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DES-1721 Specialist - Implementation Engineer, SC Series

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DES-1721 exam Dumps Source : Specialist - Implementation Engineer, SC Series

Test Code : DES-1721
Test designation : Specialist - Implementation Engineer, SC Series
Vendor designation : EMC
exam questions : 59 existent Questions

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EMC Specialist - Implementation Engineer,

massive alterations for Dell EMC Certification software | killexams.com existent Questions and Pass4sure dumps

Written with the aid of Ed Tittel posted: eleven may additionally 2018

a yoke of years after the acquisition of EMC by course of Dell, the now-hybrid Dell EMC certification application has completed a makeover. those conventional with the historical EMC certification schema will believe reform at home.

Couple discussing business on steps with laptopin case you enjoy Pixar films, then you definately probably already comprehend it’s cost staring at the credits the entire approach through on most of them. The animators always encompass just a few tiny surprises as the prolonged evolution of names, roles, and grateful acknowledgements parades across the reveal.

one in barnone my favorite credit crawl Easter eggs rolls previous on the halt of finding Nemo, when a tiny exiguous fish engulfs and gulps down an even bigger piscine passerby. I point out this as a result of besides the fact that EMC is not the biggest portion of Dell, its lengthy-time and fairly a hit certification software seems to gain gained out in defining Dell technologies' future outlook on, and constitution for, IT certification.

(EMC changed into obtained with the aid of Dell technologies on Sept. 7, 2016, when both groups formally culminated their merger eleven months after aphorism a list-environment $67 billion cash-and-stock deal.)

in order for you proof for your self, then argue with the Dell EMC “Certification Overview” web page — or more advantageous yet, down load the Dell EMC confirmed knowledgeable Certification Framework (PDF document), which lays out the total set of the enterprise’s offerings across 6 pages of content:

there's an profile page, one web page for each of 4 tracks — control, diagram and Design, deploy, and advocate — and a ultimate page that suggests certification tiers and tracks. That terminal web page is what furnished the lifelike that accompanies this story, definitely. Behold:

Ed T motif 1 05 11 2018

supply: Dell EMC Certification Roadmap, web page 6 (PDF document)

Digging into DellEMC Certification

If certification is a online game of numbers, then the Dell EMC portfolio has lots of them to offer:

● four stages: affiliate (“fundamentals training and potential of a technology”), specialist (“function particular practising, baseline abilities in a given know-how”), knowledgeable (“advanced competencies and adventure in one or extra technologies”), and master (“area subsist counted expertise with adventure in divorce applied sciences and complicated options”)● eight certification tracks: technology Architect (TA), Cloud Architect (CA), commercial enterprise Architect (EA), Implementation Engineer (IE), programs Administrator (SA), Platform Engineer (PE), Technical aid Engineer (TSE), and statistics Scientist (DS)● 7 applied sciences: (page 1 suggests how they tie into this matrix of tracks and levels) Cloud, Storage, statistics coverage, Server, Networking, Converged Infrastructure, and facts Science● The control roadmap (page 2) shows 4 divorce affiliate exams, 13 expert tests, 5 professional assessments, and a sole master exam. It additionally makes point out of CompTIA Server+, two product/expertise exams, and Dell associate and expert assessments in networking and servers. It even mentions VCP VMware credentials as well. (VMware turned into bought by course of EMC in 2004, and they gain already outlined how EMC came to subsist where it now's.)● The diagram and Design roadmap (web page 3) shows four divorce associate checks, 7 professional tests, 3 knowledgeable checks, and the same, sole grasp examination.● The installation roadmap (web page four) shows four divorce affiliate tests, 13 specialist exams, four knowledgeable assessments, but no master exam. It additionally comprises 2 product/know-how tests, and Dell associate and expert assessments in networking, VxRail equipment, and PowerEdge. It too mentions the CompTIA Server+ exam as smartly.● The steer roadmap (web page 5) indicates a sole associate exam, 7 professional assessments, 1 expert exam, but no master exam, both. It additionally includes Dell affiliate and knowledgeable checks in networking and PowerEdge. The CompTIA Server+ exam additionally places in an look.

The context for the learn here by CompTIA Server+ appears to subsist as a prerequisite for exams involving the Dell PowerEdge server household.

The EMC offerings give the tolerable framework for the course certs are labeled and categorised, and EMC's former certification regime too looks to define the evolution throughout degrees from associate to master.

There’s a all lot to absorb here, nevertheless it seems enjoy a substantial and fairly neatly-orchestrated attempt to convey the quite a few threads of training and certification collectively below the Dell EMC umbrella. subsist sure to try it out!

in regards to the creator

ed-tittel120Ed Tittel is a 30-plus-year computing device business veteran who's labored as a software developer, technical marketer, advisor, author, and researcher. author of many books and articles, Ed blogs on certification themes for Tom’s IT seasoned, and on home windows desktop OS matter matters for TechTarget. check out his web page at www.edtittel.com.


The superior ebook to NetApp Certifications — Overview & profession Paths | killexams.com existent Questions and Pass4sure dumps

NetApp specializes in information storage and administration and is optimum accepted for its line of storage techniques known as NetApp filers. This terminology reflects the storage model that the company makes utilize of, which is file oriented This stands, in distinction, to dam storage systems from other vendors corresponding to EMC, Hitachi facts programs, and IBM. NetApp’s items initially used NFS and SMB protocols for storage communications, whereas the obscure storage system uses generic SAN technology carried out using Fibre Channel. In 2002, NetApp delivered obscure storage to its capabilities.

NetApp Certification application Overview

NetApp operates an lively and densely populated certification software. It offers a total of 14 credentials, damaged into three degrees across 5 job roles: Implementation Engineer, Storage Administrator, aid Engineer, setting up Engineer, and Converged Infrastructure. Its certification levels are moderately regular for a lot of IT certification courses and comprise birthright here:

associate Entry-stage NetApp storage administration roles that target junior to mid-career IT professionals who toil with NetApp storage programs and instruments. there is a sole NetApp affiliate credential: the NetApp licensed Storage associate — Hybrid Cloud.

SpecialistMid-profession to senior-stage IT authorities who specialize in one or greater NetApp topical or platform areas. These comprise a few SAN specialist credentials (E-sequence, data ONTAP 7-Mode and ONTAP), a data insurance diagram expert credential, an ONTAP specialist, the Cisco and NetApp FlexPod Design expert, and the Cisco and NetApp FlexPod Implementation and Administration professional.

skilled Mid-career to senior-stage IT gurus who exploit or deploy all NetApp-primarily based storage environments. These encompass NetApp licensed facts Administrator credentials in each Clustered data ONTAP and records ONTAP 7-Mode, NetApp certified Storage installing Engineer, Clustered information ONTAP, and NetApp certified steer Engineer.

NetApp Implementation Engineer

professional

· NetApp certified Implementation Engineer — SAN professional, ONTAP

· NetApp certified Implementation Engineer — records coverage expert

· NetApp licensed Implementation Engineer — SAN professional, facts ONTAP 7- Mode

· NetApp certified Implementation Engineer — SAN expert, E-series

knowledgeable

· NetApp certified information Administrator, ONTAP· NetApp licensed records Administrator, statistics ONTAP 7-Mode

Storage Administrator

knowledgeable

· NetApp licensed statistics Administrator, ONTAP

skilled

· NetApp certified records Administrator, records ONTAP 7-Mode

affiliate

· NetApp certified Storage associate — Hybrid Cloud

assist Engineer

expert

· NetApp certified aid Engineer — ONTAP expert

professional

· NetApp licensed aid Engineer

installation Engineer

skilled

· NetApp certified Storage installation Engineer, ONTAP

Converged Infrastructure

expert

· Cisco and NetApp FlexPod Design expert· Cisco and NetApp FlexPod Implementation and Administration professional

NetApp associate-degree Certification

at the moment, NetApp makes it workable for a sole associate certification. The NetApp licensed Storage affiliate — Hybrid Cloud (NCSA-HC) identifies people who gain demonstrated a primary abilities of NetApp data storage and management techniques, in addition to hybrid cloud applied sciences and products. These individuals duty indispensable administration of NetApp storage controllers working records ONTAP OS, cloud configuration and management (cloud storage, ONTAP Cloud, Cloud manager, Alta Vault), and gain primary technical potential of AltaVault, StorageGrid, and OnCommand management solutions.

NetApp specialist Certifications

The Cisco and NetApp FlexPod certifications (Design and Implementation and Administration versions) headquarters of attention on converged NetApp options that mix statistics storage, networking and server features into bendy architectures to service various enterprise workloads, always in digital machines. FlexPod hastens deployment of infrastructure and business-crucial applications and reduces can charge, complexity, and chance. The Design expert goals primarily at NetApp and partner personnel and requires exam NS0–one hundred seventy; the Implementation and Administration expert is more accepted and comprises exam NS0–171. There are no formal necessities, however NetApp suggests that candidates possess 6 to twelve months of direct journey working with FlexPod options, evaluation tools and requisites, and performance requirements.

There are four other specialist credentials, which drop beneath the Implementation Engineer role, together with:

· NCIE — SAN expert, ONTAP· NCIE — SAN professional, information ONTAP 7-Mode · NCIE — information protection specialist· NCIE — SAN specialist, E-collection

The NCIE — SAN expert, ONTAP and data insurance policy expert credentials each and every require the NetApp certified facts Administrator, ONTAP (NCDA-ONTAP) certification as a requirement, while the SAN professional information ONTAP 7-Mode credential takes the NCDA 7-Mode as a prereq. There are no prerequisite certifications required for the NCIE — SAN professional, E-sequence certification. That referred to, at the least six to twelve months’ relish is advised for barnone professional candidates.

NetApp too gives sole professional Certification in the steer Engineering function — the NetApp certified assist Engineer-ONTAP professional. The NCSE-ONTAP specialist credential proves a candidate’s talents of networking, protocols, troubleshooting SAN and NAS, WAFL, SMB, NFS, structures, and storage, as well as records ONTAP. moreover passing the NCSE-ONTAP examination, the credential takes the NCSE as a prerequisite.

NetApp skilled Certifications

The NetApp licensed information Administrator (NCDA) seems in two versions: 7-Mode and ONTAP). This certification documents individual with proven competencies with in-depth help, administrative features, and performance administration for NFS and home windows CIFS multi-protocol environments. They recognize a course to achieve high- availability controller configurations, and gain sure talents of SnapMirror, SnapRestore and SnapVault applied sciences used to manage mission-vital information. Candidates for 7-Mode pick the NS0–a hundred and fifty five examination, and ONTAP candidates pick the NS0–159 examination. No necessities are required; youngsters, NetApp recommends that candidates possess as a minimum 6 to twelve months of event working with multiprotocol statistics storage environments, including administration and implementation.

The NetApp licensed assist Engineer (NCSE) files people able to delivering on-web site or remote aid for NetApp data storage techniques running the statistics ONTAP OS in NFS and home windows CIFS multiprotocol environments. different abilities tested encompass common troubleshooting and intuition isolation, documentation, hardware alternative, node configuration application and firmware improvements for NetApp methods. No prereqs are crucial, however NetApp means that applicants first obtain the NCDA certification and preserve at least 6 to twelve months’ purposeful event. A sole examination (NS0–191) is required.

The NetApp certified Storage installing Engineer, ONTAP (NCSIE) targets authorities engaged for the installation of NetApp ONTAP environments. foremost candidates gain to subsist well-versed in barnone phases of ONTAP storage options, including testing, troubleshooting, setup, lighting, and configuration. The NCDA, along with 6 to 365 days of experience, is counseled. exam NS0–181 is required to earn the certificates.

professionals working in storage administration may too obtain the NetApp certified records Administrator (NCDA) which is available for ONTAP and information ONTAP 7-mode. The NCDA proves a candidates’ competencies of administration of NetApp facts storage controllers, SnapVault, SnapMirror, managing, SnapRestore, NetApp controllers in towering availability, multiprotocol environments, storage architecture, and storage provisioning. NCDA-ONTAP candidates pick the NSO-159 exam whereas NCDA-7-Mode candidates pick the NSO-155 examination.

NetApp Jobs

NetApp job roles headquarters of attention on the forms of positions that IT gurus with NetApp learning are likely to focus on.

Implementation EngineerThis is a mid-degree to senior IT professional who concentrates on designing and configuring NetApp options for deployment, together with integration and provisioning issues.

Storage AdministratorThis is an entry-degree to senior IT professional who operates and manages storage environments in accordance with NetApp segments at various stages of tryst and responsibility.

support EngineerThis is a mid-stage IT expert who provides both or each of on-site and remote help, accustomed troubleshooting and hardware substitute intuition isolation, node configuration documentation, and application and firmware improvements for NetApp storage techniques operating the enterprise’s facts ONTAP OS in NFS and windows CIFS multiprotocol environments.

installing EngineerThis is a mid-profession to senior IT expert who performs installations of clustered NetApp environments barnone over preliminary outfit deployments and subsequent improvements and build-outs.

Converged InfrastructureThis is a mid-career to senior IT professional who works in hybrid Cisco and NetApp environments to design or do in accommodate and manage hyper-converged infrastructure environments. The environments mix Cisco and NetApp computing, storage and community infrastructure elements.

To obtain a course of job chances accessible for NetApp licensed consultants, I performed a private quest of a yoke of job websites to gain in mind what class of need exists. I discovered 2,000 job postings from employers searching for NetApp experts on SimplyHired and truly while LinkedIn produced greater than 3,000 job posts through itself. each one of these job postings fell inside the parameters for administrator and engineering roles, although there were a number of employers seeking NetApp-certified people to fulfill analyst, advertising, and architectural applications.


The optimum-paying tech jobs you can obtain in SA without a even | killexams.com existent Questions and Pass4sure dumps

no longer everyone has the possibility to Go to college and obtain a level, but the first rate tidings is that it’s no longer always obligatory to land a high-paying job.

Many organizations cost capabilities and adventure higher than a tertiary qualification, and are willing to employ people without a level.

DVT CEO Jaco van der Merwe instructed MyBroadband that the principal shortage of abilities in some areas imply that unqualified experts with tough relish can land a excessive-paying job.

cyber web options concurred, announcing there are some fields where the reform expertise, journey, and certifications can land a candidate a profitable place.

Showmax CTO Mike Raath observed that for a application engineer, he would enjoy to discern a degree in computing device science, or an acceptable engineering self-discipline.

“however, in a scarce-potential market as they have, a person who can parade their capacity through their achievements, corresponding to applications they gain got developed and correctly submitted to the Google Play shop or Apple App keep, can import for an tainted lot,” spoke of Raath.

Derivco talked about they opt for builders who've a BSc computer Science or assistance systems diploma, or an IT Diploma.

you probably gain a confirmed song list, although, and if you are a guru in .web however haven't any skills, the enterprise is raring to fulfill you.

smartly-paying IT jobs the site you don’t want a level

under are one of the high-paying tech jobs which that you may obtain devoid of a degree.

The salaries offered are in line with senior-stage salaries from CareerJunction’s April 2015 earnings evaluation.

on-line job commercial information changed into used when the career turned into now not accessible within the CareerJunction document.

Senior Java and Microsoft builders – R43,965 per 30 days

software builders stay well-known in South Africa, with senior Java and Microsoft developers ranking inordinate on the list of preferred advantage.

counseled certifications: Oracle certified knowledgeable Java Programmer; Microsoft certified expert Developer.

Java

Java

cellular App Developer – R41,092 monthly

Android and iOS builders are in inordinate demand, as many businesses are searching for applications aimed toward cellular instruments.

Mobile app development

Mobile app development

look at various automation professional – R43,000 per 30 days

verify automation experts are accountable for testing the automation of techniques.

This contains performance checking out, load testing, test administration, verify automation assist, and code stage learn at various automation.

informed certification: certified software check Automation professional.

Software testing

Software testing

security trying out professional – R41,083 per month

A protection testing expert gain to subsist sure that IT programs are relaxed. this may encompass ethical hacking, network protection compliance, penetration trying out, and more.

advised certification: licensed utility safety specialist; certified utility safety Tester.

Security testing

Security testing

Senior Agile train – R47,040 monthly

An Agile train is chargeable for helping americans undertake the Agile approach of their jobs. Their learning comprise crew coordination, requirement analysis, planning, construction, checking out, and venture potential.

advised certification: PMI Agile certified Practitioner.

IT management

IT management

Scrum master – R47,040 per thirty days

A scrum grasp is the facilitator of a product structure team that uses scrum, a rugby analogy for a evolution methodology that allows a crew to self-organise and build alterations rapidly.

The scrum master manages the mode of how counsel is exchanged.

informed certification: licensed Scrum instruct.

Scrum master

Scrum master

Hadoop specialist – (suggested with the aid of companies)

A Hadoop specialist has huge talents of Apache Hadoop – an open-supply utility framework written in Java for allotted storage and disbursed processing of significant information units on desktop clusters.

informed certification: HDP licensed Developer; HDP licensed Administrator.

Hadoop

Hadoop

Python developer – R43,965 per thirty days

Python developers utilize Python – an interpreted, object-oriented, high-level programming language with dynamic semantics – to help functions.

Programming

Programming

Puppet Labs specialist – (suggested through organizations)

Puppet Labs offers automation application to the market. Its primary product, Puppet business, contains of a commercially-supported version of its open-source configuration management tool: Puppet.

informed certification: Puppet professional; Puppet Developer.

Puppet Labs

Puppet Labs

Open-source expert – R37,593 per thirty days

Open-supply consultants are skilled and experienced within the utilize and implementation of open-source utility.

Open source

Open source

Cisco, Huawei, and EMC licensed builders – R43,965 per thirty days

a wide gain of builders are on the competencies scarcity list, together with Cisco, Huawei, EMC, and Microsoft licensed builders.

informed certification: CCENT, CCNA, CCNP, CCIE, EMC confirmed professional application, HCNA, HCNP, HCDP, and HCIE.

Programming

Programming

systems Administrator – R35,667 per month

A outfit administrator manages the operation of a pc system or electronic communication carrier.

suggested certification: Microsoft licensed IT skilled; Linux expert Institute Certification.

Systems administrator

Systems administrator

NOC Administrator – R35,667 per thirty days

A network operations centre administrator supervises, displays, and maintains a telecommunications network.

suggested certification: Microsoft certified IT expert; Linux professional Institute Certification.

NOC

NOC

more on IT salaries in South Africa

IT salaries in South Africa in 2015

Tech jobs with the optimum stress tiers

The degrees in an pains to obtain you the optimum starting revenue in South Africa


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Know pangolins before it’s eaten to extinction | killexams.com existent questions and Pass4sure dumps

KOTA KINABALU: Elisa Panjang, a distinctive designation for a Sabahan native, is not just your tolerable Kadazandusun lass.

This PhD student from Cardiff University has a keen interest in pangolin ecology and behaviour studies, and is actively involved in conservation programs to protect the endangered wildlife species.

Pangolins, too known as scaly anteater, are a mammal inhabiting tropical forests, dehydrate woodlands and the savannah.

It is believed to subsist among the most trafficked wildlife in the world. enjoy most other pangolin species, the Sunda pangolin organize in Sabah is hunted for its skin, scales, and meat.

Born and raised in Sandakan, Elisa too holds a B.Sc. (Hons.) in Conservation Biology and a M.Sc. in Ecological Processes, both from Universiti Malaysia Sabah, and added to that has a Diploma in Civil Engineering from Politeknik Kota Kinabalu to boot.

Elisa, who decided to change her course to pursue her interest in nature and wildlife, is a member of the IUCNSSC Pangolin Specialist Group and is currently fully based at Danau Girang realm Centre.

Here she conducts her research, and sometimes accomplish her job as a Pangolin Conservation Officer, educating and raising awareness about pangolins in Sabah.

After finishing her study, Elisa hopes to utilize her learning and experiences to collaboratively help the implementation of biodiversity conservation in her country.

Pangolins are completely covered with scales made of keratin, too organize in human nails, which start off as soft and season as the creatures obtain older. The armour-like scales approach into play when pangolins are under attack, when they curl up into a spiky ball.

Its scales are sometimes made into rings as charms against rheumatic fever or powdered as traditional medicine.

Its meat is eaten by those who believe it to subsist capable for health or as a heal for arthritis, asthma and back pains.

None of these conjectural uses are backed by scientific evidence, Elisa painfully points out.

“The claim is mostly driven by the Chinese, and indigenous people who hunt for wildlife. As conservationists, they are battling to deliver the pangolin, the most illegally traded animal in the world, before it is ‘eaten to extinction’, she states as a matter of fact.

The Sunda pangolin, the only species organize in Sabah, is protected under Schedule 2 of the Wildlife Conservation Enactment 1997, significance any hunting or possession requires a licence. Unlicensed hunting is punishable with a maximum penalty of five years’ jail, a fine of up to RM50,000 or both.

“I grew up in a village in Sandakan, surrounded by forest and I first saw a pangolin when I was 10 years old. I was playing outside and saw one walking towards the trees from around my house. I believe I fell in carefor with pangolins that day because of its weird look, with its scales, the course it moved and so on.

“I ran to my mom to expose her the animal. She told me the creature was called ‘tenggiling’ (pangolin in Malay) – which too sounded weird to me at that time. Before this, I had never even heard of  ‘tenggiling’ let alone pangolins, but then they became one of my favourite animals.

“I chose to study pangolins because they are so mysterious, understudied and sadly, endangered. I believe there are many things about them that they don’t know and I am interested to uncover these mysteries as well as subsist the voice for the species.

“I started my study on pangolins in 2011 so it’s almost seven years now. Working with poachers is not current to me. I am too a Sabah Wildlife Department Honorary Wildlife warden so I sometimes patrol known hotspots where poachers wander.”

To treasure what Elisa is doing is indeed capable news? She turns out to subsist the only Sabahan and Malaysian ever to execute a PhD on pangolin with Cardiff University, thanks to the occasion provided by DGFC Kinabatangan.

One must obtain at least a glimpse on the extent of the tainted news.

The tainted tidings is at a staggering US$7,000 (approximately RM30,000) per head, wild pangolins are being rapidly hunted to depletion as it has become the most trafficked wild mammal in the world, for both its scales and meat.

The spectre of doom is not far-fetched, given spectacular tidings enjoy Vietnamese Customs seizing 6.2 tons of frozen pangolin meat from Indonesia not too long ago. Sabah contributed to 22,000 Sunda pangolins killed in 2009.

In December 2011, a newly-formed Special Marine squad seized 178 containers holding 1,068 frozen pangolins worth US$1.26 million, Sabah’s largest seizure of pangolin meat in history, after a wild goose boat chase in the East Coast, making it portion of the 23,400 pangolins confiscated worldwide between 2011 and 2013 alone.

Elisa said she’s not surprised by it.

“Sabah is considered one of the hotspots for smuggling, enjoy a point for their pangolins and too other pangolins from

the Philippines forward to Vietnam and China and so for me, enforcement, education and research is what they need to execute to obtain more information, and this is very important,” she said.

The IUCN estimated over one million pangolins were killed for meat and scales over the terminal decade.

“I am a member of the IUCN Specialist Group on pangolins so I know this is true. It’s really tainted and then in Sabah, despite it being protected, the authorities still find people capturing them, at road blocks,” Elisa said.

But barnone these known reports are probably just the tip of the iceberg on this mushrooming illegal trade.

“For me, they need to execute something about the illegal trade. Without tough measures to nick down or shut down claim and effectual measures to create pangolin strongholds in their home ranges in Africa and Asia, the survival of this uncharismatic armour-plated termite and ant-eating creature will subsist lost to a gruesome trade for its meat, foetus included, and scales.

“The problem is captive breeding had proven very difficult and breeding in the wild is just one offspring per year, never really enough to replace the population lost at the current rate. Once a species is gone, it’s extinct forever.”

To add to the problem, even conservationists tend not to give focus to this solitary, nocturnal creature as they are pre-occupied with bigger, more Famous species enjoy the elephants which are being killed at 35,000 per year for ivory and the rhinos being slaughtered at 810 heads per year.

Elisa lamented: “It is really wretched because birthright now pangolins are unpopular, not many people know about it, people don’t understand them and then they are losing them rapidly while the world still doesn’t know about them.”

Under its current exciting progression – Borneo Jungle Diaries – SZtv presents environmental photojournalist, Aaron ‘Bertie’ Gekoski, who follows Elisa to tag a Sunda pangolin for the first time ever in the jungles of Borneo.

All episodes will gain Bahasa Malaysia subtitles and subsist released on SZtv and DGFC Facebook page, as well as Scubazoo.tv

and Youtube @ScubazooTV. The episodes will too subsist featured on The Daily Express, Malay Mail Online and BorneoToday.

What’s more, viewers are encouraged to pick portion in the competition that is being held; barnone you gain to execute is reply five questions from the episode correctly each week to win a 4 day / 3 night stay at the Danau Girang realm Centre.

There will too subsist a imposing prize at the halt of the 10-series Borneo Jungle Diaries for those who got barnone questions birthright across barnone quizzes.

For more information, check out http://www.scubazoo.tv/borneo-jungle-diaries/

What execute you believe of this story?

  • Brazil Water Learning progression | killexams.com existent questions and Pass4sure dumps

    Seminar 1

    Boris E. Utria Country Operations Adviser & Head of OfficeWorld Bank GroupBrasilia, Brazil

    Boris E. Utria began his career at the World Bank in 1988. In August 2010 took over as Country Operations Advisor for the World Bank in Brazil. Among several other functions of his current position, he is accountable for managing the investment pipeline and portfolio of the World Bank in Brazil, managing the Country Office in Brasilia and is the Country Focal Point for South-South Cooperation and Gender evolution in Brazil. Prior to assuming this position, Mr. Utria held various other senior positions at the World Bank, in the realm and in Washington DC, including, Acting Country Director for Mozambique, Angola, Malawi, Zambia and Zimbabwe (AFMMZ), Acting Country Manager AFMMZ, Sector Leader for Sustainable evolution for AFMMZ,  Leader of the Thematic Group on Energy and Poverty of the World Bank, Regional Program Manager for Renewable Energy for Africa (RPTES – a World Bank-DGIS Program,), and Senior Economist at the Energy Unit for Africa. 

    Before joining the Bank Mr. Utria worked as Senior Regional Planner at the Department of Regional evolution of the Organization of American States (OAS) from 1982 to 1988.  Mr. Utria began his professional career as Research Associate at the headquarters for Technology PROMON (Rio de Janeiro), and has Masters Degrees in Agricultural Economics and Regional Planning from the University of Guelph, Canada, and a B.A. Honors in Economics from the Catholic University of Rio de Janeiro (PUC-RJ).

    Thadeu Abicalil Senior Water and Sanitation SpecialistWorld Bank GroupBrasilia, Brazil 

    Mr. Abicalil, a Brazilian national, joined the Bank in 2007 as Senior Water and Sanitation Specialist. He has been working extensively in the Brazil water, sanitation and urban portfolios, leading several investment and policy evolution lending operations to federal, state and municipal institutions. He participated in the evolution of the joint World Bank and IFC Subnational Finance loans to subnational water and sanitation utilities, and has contributed to Bank financed projects and technical assistance in water and urban evolution in the Africa and Asia regions. He is too known for his expertise on issues such as subsidies, regulation and local economic development, and being a key participant in the country's sector dialogues.  

    Prior to his arrival at the World Bank, Mr. Abicalil worked as Senior Adviser for the Brazilian Association of state Water and Sanitation Utilities (AESBE) and as the coordinator of the Federal Water Sector Modernization Program, a program that combined TA at federal even and subnational levels and investments for 3 state utilities. Prior to those assignments, he was the senior advisor for the National Secretary for Urban Development. At the local government level, he worked for the Municipality of Angra dos Reis as Municipal Secretary for Works and Public Services leading the water supply and sanitation services. He has too worked at the IDB, UNDP and CEPAL in Brazil and in Uruguay, Mexico and India. His degrees are in Architecture and Urban evolution from the Federal University of Rio de Janeiro.

    Rosa Maria Formiga Johnsson Adjunct Professor at the Universidade execute Estado execute Rio de Janeiro – UERJ (Department of Sanitation Engineering and the Environment)Director of the Water and Land Management at the Institute for theEnvironment (INEA) in Rio de Janeiro 

    Ms. Formiga-Johnsson graduated in Civil Engineering in 1987 from the Universidade Federal de Goiás. She obtained her Masters (1992) and Doctorate in Environmental Sciences from the Université de Paris XII, France.  Currently, she is an Adjunct Professor at the Universidade execute Estado execute Rio de Janeiro – UERJ (Department of Sanitation Engineering and the Environment) and the Director of the Water and Land Management at the Institute for the Environment (INEA) in Rio de Janeiro. Ms. Formiga-Johnsson has too been involved in the areas of policy, planning and water management, management of hydrographic basins, hydric resource economics, environmental management, land management, cataclysm risk management and climate global change/vulnerability and adaptation.

    Ede Jorge Ijjász-VásquezDirector for Sustainable Development, Latin American and the Caribbean RegionWorld Bank GroupWashington, DC

    Ede Jorge Ijjász-Vasquez is the Director for Sustainable evolution of the Latin America and Caribbean Region, covering the areas of infrastructure (transport, energy, water supply and sanitation, and other municipal services), environment and climate change, convivial development, agriculture and pastoral development, cataclysm risk management, and urban development. The Sustainable evolution Department of the LAC region has a diversified lively portfolio of about $17 billion.

    Prior to this position, Mr. Ijjász was the Sector Manager of the Sustainable evolution Unit for China and Mongolia and was located in Beijing, China.  Mr. Ijjasz was too the manager of the Water and Sanitation Program (WSP) and the Energy Sector Management Assistance Program (ESMAP). WSP and ESMAP are two of the longest-running global trust-funded confidence fund partnership programs administered by the World Bank, supporting technical assistance and capacity structure activities in the water, sanitation and energy sectors.

    Earlier in his career at the World Bank, Mr. Ijjász was a Senior Water and Sanitation Specialist with the World Bank’s Europe and Central Asia region, and program team leader for water and sanitation projects in Central Asia, the Caucuses and the Russian Federation.

    Mr. Ijjász is currently a lecturer with the Environmental Science and Policy Master’s Program of the Johns Hopkins University in contaminant destiny and transport modeling and policy. While live in Beijing, he too taught a course in Sustainable evolution at Tsinghua University in Beijing.

    He holds a Ph.D. and a M.Sc. from the Massachusetts Institute of Technology (MIT) in civil and environmental engineering, with specialization in hydrology and water resources. He has several publications in civil engineering, physics and geomorphology scientific journals. His most recent engage is on Sustainable Low-Carbon City evolution in China.


    Photovoltaic materials: Present efficiencies and future challenges | killexams.com existent questions and Pass4sure dumps

    Photovoltaics (PV), which directly transform solar energy into electricity, present a practical and sustainable solution to the challenge of meeting the increasing global energy demand. In recent years, the decreasing cost of PV systems has levelized the cost of PV-produced electricity to the point that it can now compete with the variable portion of consumer electricity prices in many countries worldwide: The point of “socket parity” has been reached (1). Substantial further cost reduction is needed, however, to allow PV to compete in more electricity markets and to enter the multi-terawatt regime. Aside from the solar cell and module fabrication costs, a major and increasing fraction of the cost of PV generation (typically 50%) is related to component and installation requirements such as inverters, cabling, mounting structures, and labor (1). As a result, solar cell efficiency is a key lever for PV cost reduction: For a given output power, a higher cell efficiency directly translates into a smaller and therefore less expensive PV system, reducing the levelized cost of electricity. A higher power generation rate per unit zone is too principal in urban environments where space is limited. The evolution of PV materials is experiencing an stupendous growth, and efficiency records are continually broken. Below, they systematically compare the state of the art of the 16 most studied geometries of PV materials, with stress on the limitations of each material and its potential for further improvement and large-scale application.

    Solar cells are made of semiconductor materials; given the broad solar spectrum, their fundamental efficiency confine is determined by several factors (Fig. 1). Photons with energies below the band gap are not absorbed, whereas photons with energies above the band gap are not fully converted to electrical energy because of thermalization of pervade carriers (Fig. 1A, inset). Taking these two factors into account, ∼45% of the incident spectrum-integrated solar power remains for semiconductors with a band gap of 1.1 to 1.4 eV. This is the maximum power that would subsist generated if the cell were operated at a voltage corresponding to the band gap energy and a current corresponding to full capture of barnone photons with energy above the band gap, followed by full collection of barnone generated carriers.

    (A) AM1.5 solar spectrum with divorce dips due to molecular absorption in Earth’s atmosphere. Photons with energies below the band gap (Eg, dashed black line corresponds to the band gap of Si) are not absorbed, whereas photons with energies above the band gap are not fully converted to electrical energy because of thermalization of pervade carriers. The maximum power generated by the cell is limited by voltage loss relative to the band gap voltage. Inset: Electronic band structure with the separation of the quasi-Fermi levels determining the open-circuit voltage Voc. (B) theoretical Shockley-Queisser detailed-balance efficiency confine as a duty of band gap (black line) and 75% and 50% of the confine (gray lines). The record efficiencies for different materials are plotted for the corresponding band gaps.

    Even in an exemplar case, however, the open-circuit voltage Voc is always lower than the band gap energy because thermodynamic circumstantial equilibrium requires the cell to subsist in equilibrium with its environment, which implies that there is impulsive light emission from the cell. The corresponding radiative carrier recombination represents a black current that causes Voc to subsist well below the band gap voltage Vg (Fig. 1A, inset). Furthermore, under maximum-power operation (at maximum J × V), the voltage Vmp is lower than Voc and the current density Jmp is lower than the maximum (short-circuit) current density Jsc (Fig. 2A, inset). The efficiency confine that takes barnone these factors into account was first derived by Shockley and Queisser (S-Q) in 1961 (2). motif 1B shows this limiting efficiency for a single-junction solar cell under “one-sun” illumination with the measure AM1.5 solar spectrum as a duty of band gap; the maximum efficiency occurs for a semiconductor with a band gap of 1.34 eV and is 33.7%.

    Single-junction solar cell parameters are shown as a duty of band gap energy according to the Shockley-Queisser confine (solid lines) and experimental values for record-efficiency cells. (A) Short-circuit current Jsc. Inset: A typical current-voltage J(V) curve, with Voc, Jsc, Vmp, and Jmp indicated. The product of current and voltage is highest at the maximum power point (JmpVmp). (B) Open-circuit voltage Voc. The voltage corresponding to the band gap is shown for reference, with the voltage gap Vg-VSQ indicated by the gray shaded region. (C) Fill factor FF = (JmpVmp)/(VocJsc). barnone data are for measure AM1.5 illumination at 1000 W/m2.

    In practical solar cells, not barnone incident light is absorbed in the lively layer(s) and not barnone generated carriers are collected; hence, Jsc is below the maximum value that can subsist achieved for a given band gap, Eg. The achievable Voc is too reduced below the S-Q value by such phenomena as Auger recombination, band tail recombination, and recombination at bulk, interface, and surface defects (3–5). Furthermore, resistance and contact losses and other nonidealities reduce the fill factor FF = (JmpVmp)/(VocJsc). Combined, these factors lead to practical efficiencies that are often substantially lower than the S-Q confine for a given band gap.

    Ideal and record-efficiency solar cells compared

    We distinguish three classes of PV materials: (i) ultrahigh-efficiency monocrystalline materials with efficiencies of >75% of the S-Q confine for the corresponding band gap: Si (homojunction and heterojunction), GaAs, and GaInP; (ii) high-efficiency multi- and polycrystalline materials (50 to 75% of the S-Q limit): Si, Cu(In,Ga)(Se,S)2 (“CIGS”), CdTe, methyl ammonium lead halide perovskite [CH3NH3Pd(I,Cl,Br)3], and InP; and (iii) low-efficiency materials (<50% of the S-Q limit): micro- or nanocrystalline and amorphous Si, Cu(Zn,Sn)(Se,S)2 (“CZTS”), dye-sensitized TiO2, organic and polymer materials, and quantum dot materials.

    The record efficiency for each of these materials is plotted in Fig. 1B (see too table S1). The experimental values for Jsc, Voc, and FF for the record-efficiency cell reported for each individual material are shown in Fig. 2, A to C, together with the limiting values calculated using the S-Q model (2). The experimental values for Jsc generally supervene the trend given by the S-Q limit, with some materials closely approaching this limit. Values for Voc and FF are much more scattered, with only a few materials approaching the S-Q limit. To dissect these trends, they evaluated two characteristic parameters for each material: (i) the current ratio j = Jsc/JSQ, which indicates the degree of light coupling, absorption, and trapping in the lively layer(s) of the cell, and too depends on the carrier collection efficiency; and (ii) the voltage ratio v = Voc/VSQ, which is primarily related to the degree of recombination of carriers in the bulk, surfaces, and interfaces. Together, the voltage ratio v and fill factor ratio f = FF/FFSQ indicate the total electrical limitations of a cell (6). A plot of j versus v × f for barnone evaluated materials (Fig. 3) directly indicates to what degree the cell efficiency is limited by light management or pervade carrier management. Next, they relate these data for barnone materials.

    Fig. 3 Fraction of Shockley-Queisser detailed-balance confine for voltage and current achieved by record cells.

    The current ratio j = Jsc/JSQ is plotted versus the product of the voltage and fill factor fractions (v × f = FF Voc/FFSQVSQ) for the record-efficiency cells of barnone evaluated materials. The lines around some data points correspond to a gain of band gaps taken in the S-Q calculations according to mistrust in the band gap of the record cell. Arrows on top and birthright axes indicate how improved light management and pervade carrier collection help the cell efficiency. ηSQ denotes maximum achievable efficiency according to the SQ model.

    Silicon (efficiency 25.0 to 25.6%)

    Silicon has a nearly exemplar band gap (Eg = 1.12 eV) for reaching towering efficiency (Fig. 1). Si homojunction cells are based on a p-n junction made into either p-type or n-type Si(100) substrates. Several advanced device architectures and contacting schemes gain been developed for Si solar cells. Contact recombination represents a major source of loss, so the most successful approaches minimize contact zone (e.g., by localized heavy doping or metal deposition), implement passivated contacts, or utilize a combination of these approaches. In parallel, surface passivation of Si using Si3N4, Al2O3, SiO2, or combinations of these materials has been developed to noteworthy perfection. The record efficiency for a monocrystalline Si homojunction cell was recently set at 25.1% (7) for a cell with a full-area tunnel oxide passivated rear contact and high-quality top surface passivation (the TOPCon design; Fig. 4A), slightly higher than the value of 25.0% (8, 9) reported in 1998 for a cell that used local contacts and high-quality surface passivation [the passivated emitter rear localized diffused (PERL) design].

    Fig. 4 Layer and contact geometry for solar cells with record efficiencies above 20%.

    (A) TOPCon crystalline Si (Fraunhofer). (B) IBC crystalline Si (SunPower). (C) Heterojunction IBC crystalline Si (Panasonic). (D) Multicrystalline Si (Trina Solar). (E) GaAs thin film (Alta Devices). (F) CIGS thin film (ZSW Stuttgart). (G) CdTe thin film (First Solar). (H) Perovskite thin film (KRICT). For industrial cells, the exact geometry is not publicly available.

    The TOPCon cell has excellent current generation and collection (j = 0.96), similar to the value achieved for two other record-efficiency Si solar cell designs (table S1). This results from a combination of very low surface reflection [achieved by a pyramidal (111)-faceted surface texture combined with an anti-reflection coating (ARC)] and very low recombination losses in the Si wafer and at the surfaces and contact interfaces. Low recombination is too reflected in the relatively towering voltage of the TOPCon cell (v = 0.82).

    In a radically different design, both the p-n junction and the contacts are placed at the rear of the cell. This interdigitated back-contact (IBC) design features alternating p-type and n-type contact regions (Fig. 4B). The IBC design eliminates front contact shading losses and reduces progression resistance by allowing more metal to subsist used for current collection and transport. This comes at the cost of more challenging carrier transport in the device (carriers generated near the surface must subsist collected at the back) and requires the utilize of very high-quality material. Overall current generation and collection in the IBC cell is slightly lower than in the TOPCon cell (j = 0.95 versus 0.96), as is the record efficiency (25.0% versus 25.1%) (9–11). Note that the IBC cell has an zone of 120 cm2, whereas the TOPCon cell measures 4 cm2. The IBC cell uses a doped surface layer, which creates a front surface realm that repels carriers from the surface, and has a Si3N4 top layer that serves as both an ARC and a high-quality passivation layer for the Si surface. The lower surface and bulk recombination rates lead to a slightly higher voltage (v = 0.83) for the IBC cell relative to the TOPCon cell.

    An efficiency record of 25.6% was recently reported for an IBC Si solar cell that uses silicon heterojunctions (SHJs) rather than homojunctions for carrier collection (9, 12). In this approach, a thin stack of doped and intrinsic hydrogenated amorphous Si (a-Si:H) layers is deposited onto a crystalline Si surface to shape a junction, replacing the process of junction formation by high-temperature dopant diffusion (Fig. 4C). The SHJ design avoids carrier recombination in highly doped p-type and n-type regions and is made using a low-temperature process, which better preserves the minority carrier lifetime of the Si wafer. The surface of the record SHJ cell is passivated with a-Si:H. This design led to the highest voltage observed for a Si solar cell (v = 0.84). The overall result of carrier generation and collection is similar to that of the TOPCon cell (j = 0.96). The origins of the tiny remaining losses in these high-efficiency Si cells are quite different because of their different design and mode of operation.

    As a result of the indirect band gap of Si, the absorption coefficient is relatively low and varies only gradually around the band gap energy, so that a relatively thick wafer is required to absorb barnone light with photon energies above the band gap. This, however, leads to higher bulk (Auger) recombination and thus reduces Voc. Moreover, it increases the material costs. The present tradeoff among cost, manufacturability, and performance leads to an optimum Si wafer thickness of 100 to 200 μm for commercial cells. These wafers are made by diamond wire sawing from monocrystalline Si rods produced by Czochralski crystal growth.

    Multicrystalline Si wafers are nick from cast ingots produced using directional (unseeded or seeded) crystallization, and their fabrication cost is lower than that of monocrystalline wafers. The typical grain size depends on the growth mode and can subsist as large as several centimeters. Multicrystalline Si has a lower electronic quality, due to crystal grain boundaries and intragrain defects, as well as a higher concentration of impurities. As a result, the record-efficiency multicrystalline Si cell has large voltage loss (v = 0.76). Light trapping in these cells is less efficient because the exemplar pyramidal surface texture normally formed by alkaline-etching Si(100) to the (111) surface facets cannot subsist realized on a multicrystalline surface. This, together with incomplete carrier collection due to recombination, leads to a reduced current (j = 0.91). Together, these voltage and current losses capitulate a lower efficiency (20.8%) (9, 13) than for monocrystalline Si cells. The record-efficiency multicrystalline Si cell has a passivated emitter and rear cell (PERC) p-n junction design (Fig. 4D).

    According to the S-Q model, the efficiency confine for Si solar cells is 33.3%, far above the experimental record of 25.6%. A key limiting factor that is not accounted for in the S-Q model is Auger recombination of free carriers that occurs under illumination. Taking this into account for Si, the efficiency confine for an undoped (monocrystalline) Si cell with optimized thickness (110 μm) was calculated to subsist 29.4% (14), leaving margin for further evolution of existing technologies in the coming years.

    Today the global PV market is dominated by wafer-based crystalline Si solar modules, with a total market partake of >90%. Multicrystalline Si represents ∼65% and monocrystalline Si ∼35% of this market segment (15). PV systems based on Si solar cells installed in the realm gain been shown to present towering reliability and very limited efficiency degradation over a age longer than 25 years.

    GaAs (efficiency 28.8%)

    The record efficiency for a single-junction solar cell under one-sun illumination has been achieved using GaAs (28.8%) (9, 16). This material has a direct band gap close to the optimum (1.42 eV; Fig. 1). Because of the towering optical absorption coefficient of GaAs, the cell thickness can subsist kept relatively tiny (∼2 μm) to harvest the solar spectrum up to the band gap. The record-efficiency cell design has a n-GaAs/p-Al0.3Ga0.7As junction geometry with high–band gap window layers that serve to retain minority carriers in the GaAs lively layer (Fig. 4E). The GaAs heterostructure is epitaxially grown using chemical vapor deposition, which is a relatively energy-intensive process. Interestingly, the record efficiency was achieved using a lift-off process, in which a GaAs foil ∼2 μm thick was exfoliated from the substrate (by chemical etching of an AlAs buffer layer) and laminated onto a Cu substrate. The voltage of the record-efficiency cell is very towering (v = 0.97). Light reflection, top-finger shadowing, incomplete light trapping, and absorption in the metal back contact result in some current loss (j = 0.92), leaving margin for improvement. Application of an IBC geometry, for example, could potentially further increase j. An intermediate dielectric back-reflecting geometry can reduce parasitic absorption in the metal back contact. The fill factor in these cells is very towering (f = 0.97). Taking into account Auger recombination, the maximum efficiency that can subsist achieved for a practical single-junction GaAs cell is ∼32% (17), substantially greater than the current record value.

    Whereas III-V solar cells gain traditionally been used in niche markets requiring towering efficiency on a tiny area, such as space technology, the newly developed layer-transfer technology enables fabrication of large-area resilient (single-junction) GaAs technology at reduced cost for a much broader gain of applications. Encapsulation and recycling of commercial GaAs modules is principal because of the utilize of the toxic component As.

    InP (efficiency 22.1%) and GaInP (efficiency 20.8%)

    Two other III-V compound semiconductors that gain achieved towering efficiencies are InP and GaInP. InP (Eg = 1.35 eV) has a band gap similar to that of GaAs, but the maximum reported efficiency of 22.1% (9, 18) is much lower than for GaAs; this dissimilarity is due to both lower voltage and lower current (v = 0.81, j = 0.85). Because of the existing high-efficiency GaAs alternative and the scarcity and associated towering cost of In, developments on InP cells gain been minimal in the past decade. GaInP has a relatively towering band gap (1.81 eV), for which the S-Q confine efficiency is 25.2%. The record efficiency achieved for a GaInP cell is 20.8% (9, 19). The voltage loss on the record cell is extremely tiny (v = 0.96), but current collection (j = 0.82) in these cells leaves much margin for improvement. The record-efficiency GaInP cell has the highest fill factor achieved for any material (FF = 0.89; f = 0.98), which is partly related to the towering band gap (Fig. 2C). Because of its large band gap, GaInP is used in III-V multijunction solar cell geometries. Recently, a mechanically stacked tandem composed of a GaInP top cell and a Si heterojunction base cell was reported with an efficiency of 29.8% (11).

    CIGS (efficiency 21.7%)

    The record efficiency of Cu(In,Ga)(Se,S)2 (CIGS) thin-film solar cells has steadily increased over the past 20 years, with the present record value at 21.7% (9, 20), making it the highest-efficiency thin-film solar cell material to date, very closely followed by CdTe at 21.5% (9, 21). CIGS has a chalcopyrite crystal structure and its band gap can subsist continuously tuned between ~1.0 and 2.4 eV by varying the In/Ga and Se/S ratios, with the low–band gap compositions so far always giving the best performance. Polycrystalline films of CIGS are made using sputtering or evaporation from the constituent elements and are typically deposited onto a Mo film that is sputtered on a soda-lime glass substrate. The typical lively layer thickness is ∼2 to 3 μm. Sodium diffusing from the glass substrate into the CIGS layer has been organize to play a key role in passivating defects in the CIGS layer; the record cell too incorporated traces of K. The CIGS composition is typically graded to shape an electric realm that repels minority carriers from the Mo back contact, which is a tough recombination sink. The cell is finalized by the chemical-bath deposition of CdS to shape a heterojunction followed by an intrinsic ZnO buffer layer, a transparent ZnO:Al conducting layer (TCL), and a MgF2 ARC (Fig. 4F). In some recent high-efficiency devices, the CdS layer is replaced by the more transparent ZnOxS1–x. Indium is a key component in CIGS, and its scarcity is a concern for scaling up CIGS module production to the terawatt level.

    The voltage for the record-efficiency CIGS cells (Eg = 1.13 eV) is very high, with v = 0.84, equal to the best monocrystalline Si cells. Given the polycrystalline nature of the material, this implies that grain boundaries in this material execute not act as tough carrier recombination sites. There is substantial current loss (j = 0.84) due to light reflection, incomplete light trapping, absorption in the Mo back contact, and parasitic absorption in the CdS and ZnO:Al layers. The absorption spectrum of CIGS shows a rather gradual variation with energy around the band gap, which leads to unavoidable current loss in the near–band gap spectral range. As with barnone polycrystalline materials, improving material property is a involved process that requires optimization of many different parameters such as deposition conditions, (post-)annealing procedures, and ambients. Because of the involved stoichiometry of CIGS, many secondary phases are possible, and much of the progress in efficiency has been achieved by optimizing the deposition and annealing process to avoid such detrimental by-products. Creating a capable ohmic electrical contact between Mo and CIGS (via a MoSe2 interfacial layer) is another principal factor. Replacing the CdS buffer layer with a nontoxic and more transparent material is too a key research area.

    The possibility of band gap tuning makes CIGS an quick-witted material in tandem solar cells, either by combining CIGS layers with different band gaps or by using a high–band gap CIGS top cell on top of a Si base cell. So far, however, high–band gap (Ga-rich) CIGS cells gain not yielded adequate efficiencies for a CIGS/Si tandem to beat the record-efficiency Si cell.

    CdTe (efficiency 21.5%)

    CdTe is a binary semiconductor with a cubic zincblende crystal structure and a near-ideal band gap of 1.43 eV. It can subsist deposited at relatively low temperature using evaporation from CdTe powder. Cells are typically grown in a superstrate configuration starting from a glass substrate coated with fluorine-doped tin oxide (FTO). The subsequent layer stack usually consists of CdS (generally deposited by chemical bath deposition), followed by evaporated CdTe (thickness typically 2 to 3 μm) and a metal back contact such as Al or Ti, in some cases with a CuZnTe interfacial layer between the metal and the CdTe (Fig. 4G).

    The highest reported certified efficiency for CdTe is 21.5% (9, 21), although for the purpose of this review they dissect cells with the previous record of 21.0% (22) because circumstantial data for the current record-efficiency cell are not yet available. The precipitous absorption coefficient versus energy for CdTe enables very capable current collection in CdTe cells (j = 0.96), far superior to any other thin-film technology and equal to that of the record-efficiency monocrystalline Si cells. The towering voltage loss in CdTe cells (v = 0.75) is attributed to recombination losses in the crystal grains and at interfaces in the polycrystalline material; the exact nature of this recombination is still unclear.

    CdTe solar modules are commercially produced by several companies and gain the largest market partake among present thin-film technologies, which are dominated by CdTe, CIGS, and thin-film Si. Recycling systems gain been set up for commercial CdTe modules, which is particularly principal because of the utilize of the toxic component Cd; the scarcity of Te is too a concern.

    Methyl ammonium lead halide perovskite (efficiency 21.0%)

    Hybrid organic-inorganic perovskite solar cells gain recently taken the PV research world by storm, with efficiencies above 20% achieved after only 5 years of substantial work. These materials gain the general formula ABX3, where A is an organic cation (most often methylammonium, CH3NH3), B is an inorganic cation (usually Pb), and X is a halide [typically I, often with a tiny fraction of Cl or Br: CH3NH3Pb(I,Cl,Br)3]. Depending on the halide used, the band gap can subsist continuously tuned from ~1.6 eV (pure I) to 3.2 eV (pure Cl), with the smaller–band gap materials providing better solar cell efficiencies (23). Even smaller band gaps can subsist achieved using a different organic cation (e.g., formamidinium, H2NCHNH2) or inorganic cation (e.g., Sn), and such compounds are desirable as they gain a higher efficiency confine (Fig. 1B).

    The perovskite salts shape polycrystalline films with a perovskite structure at or near margin temperature by precipitation from a variety of polar solvents (commonly dimethyl formamide or dimethyl sulfoxide). The device geometry is usually very similar to, and inspired by, those used for solid-state dye-sensitized or polymer bulk heterojunction solar cells. Typically, an FTO-coated glass substrate is coated with an electron-selective contact (usually TiO2). Subsequently, the perovskite is deposited either by spin-coating the soluble precursors (methyl ammonium iodide and lead iodide, bromide, or chloride) or evaporating the constituent powders. A low-temperature annealing process (<150°C) often helps to help crystallinity, film morphology, and device performance. Finally, the hole-selective top contact (usually Spiro-OMeTAD, C81H68N4O8) is spin-coated on top, and the back contact (usually gold) is evaporated to finish the device (Fig. 4H).

    The record perovskite solar cell efficiency is 21.0% (9, 24), although for the purpose of this review they dissect cells with the previous record of 20.1% (9, 24) because circumstantial data for the current record cell are not yet available. This cell has a very tiny zone and exhibits a relatively tiny voltage loss (v = 0.83), even better than the record-efficiency monocrystalline Si homojunction cells, which is remarkable for a solution-processed semiconductor. Even though the absorption spectrum of perovskites shows a very sharp onset, comparable to that of the best semiconductor absorbers (CdTe and GaAs), the photocurrent loss is still substantial (j = 0.88). This loss comes primarily from parasitic absorption in the hole-conducting layer and the back reflector. The fill factor in these cells (FF = 0.73; f = 0.81) is the lowest of barnone cells with efficiencies greater than 20%, most likely because of a combination of nonuniformity in the absorber (e.g., pinholes) and carrier-selective contacts that lead to carrier shunting, along with resistive losses associated with nonideal carrier-selective contacts. The fill factor (and thus the efficiency) is expected to continue to increase as these factors are optimized further.

    Despite their excellent initial performance, hybrid perovskite solar cells are known to debase within a few hours to days under measure operating conditions; at present this is the greatest barrier to commercial implementation. The origins of perovskite cell instability are currently a topic of lively research, although photoreduction by ultraviolet light and reactions with water gain already been identified as likely candidates. Also, measurements of the current-voltage characteristics can suffer from hysteresis, making efficiency analysis complex. The root of this hysteresis is still unclear, but the leading hypothesis involves ion (or vacancy) migration under operating conditions. The perovskite salts are partially soluble in water, so the cells are sensitive to humidity. Because of Pb toxicity, encapsulation and recycling are principal for this technology to become viable for large-scale application. The toxicity challenge is greater for this material than for CdTe and GaAs because the much higher water solubility and lower vaporization temperature build environmental exposure during module encapsulation failure (breakage, fire) more dangerous. Large–band gap perovskites may serve as a top cell in Si/perovskite tandem solar cells that gain a potential efficiency above 30%; such an application provides a workable entry point to the market for the perovskite technology and is currently under fierce research.

    CZTS (efficiency 12.6%)

    Cu(Zn,Sn)(S,Se)2 (CZTS) is a solar cell material similar to CIGS, but with the scarce component In replaced by Zn and Ga replaced by Sn. CZTS can crystallize to shape either a kesterite or stannite crystal structure, with kesterite being preferable for PV applications. As in CIGS, the band gap of CZTS can subsist tuned over a substantial gain (1.0 to 1.6 eV); the best results gain been achieved for a Cu-poor, Zn-rich stoichiometry with the band gap controlled by the S/Se ratio (25). The cell structure is nearly identical to what is used for CIGS. Cell fabrication can too supervene a similar process, although the record-efficiency CZTS cells gain been made using solution deposition of chalcogenides dissolved in hydrazine followed by annealing in selenium vapor. The record CZTS cell has an efficiency of 12.6% (9, 26) and suffers from large voltage loss (v = 0.58) due to recombination at defects in the bulk material and at the pervade extraction interfaces. As with CIGS, the involved nature of the material requires study of many different types of defects and observant engineering of the fabrication and device processing to minimize the most detrimental defects. Controlling interfacial reactions at the Mo metal contact is crucial for reducing interfacial recombination and minimizing progression resistance. Current loss in CZTS cells is comparable to that of CIGS (j = 0.81). Finding an alternative back contact with lower optical loss (higher reflectivity) that can withstand the full device processing and maintain low progression resistance would subsist a major breakthrough in the evolution of CZTS solar cells, although the biggest factor limiting efficiency is the low Voc, a consequence of the relatively poor material quality.

    Dye-sensitized solar cells (efficiency 11.9%)

    Dye-sensitized solar cells are a special class of devices, as they involve an electrochemical power generation process. In these cells, the absorber is not an extended solid semiconductor but a molecular dye (typically a ruthenium organometallic complex, although zinc porphyrin and even purely organic dyes gain too given very towering efficiencies) that is coated onto a highly porous nanostructured electrode (typically TiO2). The photoexcited dye injects electrons into the conduction band of the TiO2 and accepts electrons from a redox yoke (typically I–/I3–, although higher voltages gain been reached with Co-based redox couples) in a nonaqueous electrolyte. The redox lively species must then diffuse to the counter electrode (usually Pt or graphite) to subsist regenerated and complete the current circuit. Dye-sensitized solar cells are made by depositing a very thin compact TiO2 layer typically on FTO, followed by formation of mesoporous TiO2 by printing a TiO2 nanoparticle paste, annealing, TiCl4 treatment to passivate surface traps, and finally dye adsorption by immersion in solution. A glass plate covered with the counter electrode is brought very close to the substrate using spacers, and the cell is filled with electrolyte and sealed. Here, they dissect these cells according to the S-Q model, which assumes a semiconductor absorber with an absorption band edge; although this is not the case for dye-sensitized cells, the numbers for v and j then provide a reference relative to a conventional semiconductor with a band gap equal to the peak of the dye absorption spectrum (1.50 eV).

    The record dye-sensitized cell has an efficiency of 11.9% (9, 27) with a large voltage loss (v = 0.60) due to the relatively low potential of the measure I–/I3– redox couple, which introduces a large energy loss when transferring electrons to the dye. No better dye-based alternatives gain been organize despite fierce research over the past several years: Redox couples with higher potentials either react too quickly with electrons injected into the TiO2 (leading to recombination) or are too bulky for rapid ionic diffusion through the electrolyte (leading to tough losses in the fill factor at towering light levels).

    An additional challenge for dye-sensitized solar cells is the relatively towering energy and narrow bandwidth associated with molecular absorption, which makes it difficult to harvest a wide gain of the solar spectrum (j = 0.78). Using multiple dyes introduces complications with the redox chemistry, whereas using dyes with broader spectra reduces oscillator power and requires porous electrodes to become too thick for efficient pervade extraction. Despite these difficulties, dye-sensitized solar cells gain already been commercialized because of their relatively simple fabrication, low-cost materials, and availability in a variety of colors and opacities that are useful when aesthetics are important. Moreover, dye-sensitized solar cells gain served as a model system or inspiration for the evolution of a current class of nanostructured device architectures for PV solar energy conversion and solar fuel generation.

    Organic solar cells (efficiency 11.5%)

    Organic solar cells present inexpensive roll-to-roll fabrication on resilient substrates and a wide preference of materials for applications where flexibility and color are important. Organic solar cells approach in two varieties: sublimed small-molecule solar cells and solution-processed polymer/fullerene solar cells. The highest reported certified efficiency for a single-junction organic solar cell is 11.5% (28, 29), although for the purpose of this review they dissect cells with the previous record of 11.0% (9, 30) because circumstantial data for the current record-efficiency cell are not yet available. The previous record was achieved using a polymer with a 1.66-eV band gap.

    Polymer solar cells are typically prepared on ITO-coated glass or foil with the lively polymer donor–fullerene acceptor blend sandwiched between a hole-selective layer [typically poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) or MoO3] and an electron-selective layer such as ZnO, TiO2, or a low–work duty material such as Ca. The typical lively layer thickness is ~100 nm.

    Because of the low dielectric constant of organic materials, photogenerated electron-hole pairs remain tightly bound, necessitating the utilize of dedicated architectures such as bulk heterojunctions to achieve efficient pervade separation and extraction. The energy offsets needed for the heterojunction to ensure efficient exciton dissociation lead to a voltage loss of ~0.3 eV in practice, which lowers the efficiency by about 2% absolute (31). Currently, the limiting problems for organic solar cells are the towering rate of nonradiative recombination (via trap states or triplet excited states) and the large degree of static and dynamic disorder, together yielding very large voltage loss (v = 0.57). To a large extent, this voltage loss could subsist overcome by direct optical excitation of the charge-transfer state between electron donor and electron acceptor. So far, common material combinations expose a very low oscillator power of these charge-transfer states, rendering direct optical excitation nearly absent. Substantial current loss (j = 0.82) is due to parasitic absorption by the selective contacts, incomplete absorption by the polymer, and incomplete carrier collection resulting from nonradiative recombination (low mobility and diffusion length).

    As with thin-film Si solar cells, organic PV technology is suffering from the fact that efficiency is becoming an increasingly principal driver to reduce the cost of large-area PV systems. Also, organic cells often expose degradation under illumination. At the identical time, a variety of attributes—relative ease of processing, nontoxicity, low weight, potential for low cost, and possibility of forming resilient modules of many different shapes, colors, and transparencies—enables applications that may not subsist achievable with thin-film resilient CIGS, CdTe, or perovskite cells that gain much higher efficiency.

    Thin-film silicon (efficiency 10.1 to 11.4%)

    Thin-film microcrystalline or nanocrystalline Si solar cells can subsist made on a wide gain of (flexible) substrates by means of chemical vapor deposition. Typically, a p-i-n geometry is grown on a ZnO:Al-coated textured glass substrate, followed by a ZnO:Al buffer layer and Ag back contact. The record efficiency is 11.4% (9, 32). The relatively leisurely deposition rate of crystalline Si limits the cell thicknesses that can subsist practically achieved to 2 to 5 μm, and the textured substrate often leads to defected growth of the microcrystalline film. As a result of this thickness limitation, light with energies near the band gap is not fully absorbed, leading to a very tough current penalty with j = 0.67, the lowest value of barnone cells reviewed here. Crystal grain boundaries and other defects in deposited micro- or nanocrystalline Si cells are tough sinks for minority carriers, leading to a large voltage loss as well (v = 0.61).

    Amorphous Si (a-Si:H) is a semiconductor with much stronger optical absorption than crystalline Si, but with a band gap well above the optimum (1.7 to 1.8 eV). It is made using vacuum deposition techniques, typically at a much higher rate than micro- or nanocrystalline films. Despite the incorporation of hydrogen in these films to passivate bulk defects, the electronic property of this material is rather low, with a correspondingly large voltage loss (v = 0.61) for the record-efficiency single-junction cell (10.2%) (9, 33). In a-Si:H cells, the optimum efficiency is strongly determined by the trade-off between cell thickness and carrier collection efficiency: A large thickness is required to optimize the capture of incident light, but this reduces the carrier collection efficiency if the cell is thicker than the carrier drift/diffusion length, which is typically a few hundred nanometers; for the record-efficiency cell, j = 0.78. Amorphous Si cells are most often fabricated in a superstrate configuration using a textured glass substrate coated with ITO as a transparent conductor. This then forms the starting point for the subsequent growth of a-Si:H, ZnO:Al buffer layer, and Ag back contact.

    As cell efficiency becomes an increasingly principal factor in PV cost reduction, the progress of thin-film Si technology has slowed in recent years. Yet the possibility of fabricating resilient modules using a roll-to-roll process provides unique application potential—for example, in structure architecture. Thin-film Si triple-junction cells in which amorphous and microcrystalline Si cells are stacked together gain shown a record efficiency of 13.4% (34).

    Quantum dot solar cells (efficiency 9.9%)

    Quantum dot (QD) solar cells pick edge of the fact that semiconductor quantum dots can subsist synthesized using (low-temperature) solution processing, with their band gap tunable by composition and size. The best QD solar cells so far are made using PbS or PbSe QDs as the lively layer. The QDs are deposited by spin coating or drunk coating and then passivated and functionalized using organic molecules or halide salts. A p-n junction is made in the QD layer using a combination of surface ligands. QD cells are typically made on ITO- or FTO-coated glass, using a metal oxide (typically ZnO or TiO2) as an electron-selective contact. Molybdenum oxide and Au or Ag are typically used as the back contact.

    The record published efficiency for QD solar cells is 9.9% using PbS QDs with a band gap of 1.4 eV, with an architecture similar to previous toil (35). The 9.9% cells gain very large voltage loss (v = 0.56), the largest loss of barnone cells reviewed here, which is attributed to the fact that the QDs gain a distribution of sizes that results in a distribution of band gap energies. In addition, a towering density of radiative sub–band gap states and tough nonradiative surface recombination due to the large surface-to-volume ratio in the quantum dots (diameter ∼5 nm) leads to recombination. Inefficient transport of carriers by hopping through the QD film limits the QD film thickness that can subsist practically used. Together, incomplete absorption and tough recombination contribute to a towering current loss (j = 0.66). (Note that in the analysis they utilize the first excitonic peak in the absorption spectrum as the band gap of the quantum dots; taking a smaller electronic band gap correspondingly increases v and decreases j.)

    Historical efficiency trends

    There are large differences in the rate of efficiency improvement for the different materials discussed above. For example, after more than 60 years of research, single-crystalline Si is a develope technology, and the efficiency improvements that gain been achieved in recent years gain been relatively tiny and gradual. In contrast, the record efficiency for the current perovskite materials has climbed rapidly since the first cells were demonstrated, although cells with these record efficiencies are not yet stable in efficiency.

    To illustrate recent trends in cell development, Fig. 5 compares present efficiencies with the tolerable annual increase in absolute efficiency over recent years. Crystalline and multicrystalline Si gain recently shown only gradual absolute efficiency improvements in the gain of 0.04 to 0.09% per year; the increase in crystalline Si efficiencies results from progress in Si heterojunction cells. The high-efficiency thin-film materials perovskite (2.7% per year), CdTe (0.9% per year), and CIGS (0.2% per year) gain made principal steps forward over the past few years.

    Fig. 5 Rates of improvement in solar cell efficiency over recent years.

    Average improvements were calculated over a age ending 1 January 2016 and starting with the date of the terminal record preceding 2010 [with two exceptions: perovskites (starting 2013, when the first certified efficiency was reported) and CdTe (starting 2011, as no recent record before 2010 was available and much progress occurred after 2010)]. Progress in efficiency from the pre-2010 record to the current values is indicated by the plumb lines. Colors correspond to cells achieving <50% of their S-Q efficiency confine (red), 50 to 75% (green), or >75% (blue). This analysis is based on data from the National Renewable Energy Laboratory efficiency chart, Green’s tables, and publications (11, 19, 29).

    Although these recently demonstrated efficiency increases are no guarantee of improvements in the future, the realization of large yearly increases in materials with remaining margin for growth in v, j, and f hints that research efforts gain not yet become constrained by fundamental limits. Additional research will divulge whether the record efficiency of CIGS, CdTe, or perovskite cells (now 4 to 5% below that of Si IBC cells) can exceed that of Si cells. The efficiency record for thin-film GaAs cells has not been broken since 2012; a more recent record is for thin-film III-V dual-junction cells (31.6%) (29). In the low-efficiency (10 to 12%) category, quantum dot solar cells (1.3% per year) and organic solar cells (0.6% per year) continue to build tough progress. Dye-sensitized cells and CZTS gain not reported efficiency improvements since 2012 and 2013, respectively. They note that historically, when materials are developed to the even of commercialization, further efficiency increases are often observed beyond the records first achieved in a research laboratory. For example, the present efficiency records for Si IBC, GaAs, and CdTe cells are realized in manufacturing laboratories.

    Solar module efficiencies

    Two principal factors create a gap between the record efficiency of laboratory solar cells and the record efficiency of laboratory modules or tolerable efficiency of commercial modules, respectively. First, record-efficiency cells are often small-area devices made using specialized laboratory techniques that may subsist too expensive for large-scale production. For example, thin-film vacuum deposition of metal contacts may subsist used in the lab, while screen printing of contacts, leading to much lower metal conductivity, is used in industrial fabrication facilities. Second, modules are made of a number of larger-area cells connected in progression and encapsulated. In the case of wafer-based technologies, incorporation of cells in a module inevitably leads to current loss (due to incomplete filling of the module area) and fill factor loss (due to additional resistance in cell interconnects and the utilize of larger cells). Optical effects upon encapsulation may subside or increase efficiency, depending on the specifics of module design. Efficiencies of typical thin-film modules are lower than those of corresponding record cells because of the “dead area” associated with monolithic interconnection of strip-like cells, inhomogeneities or imperfections in the larger areas of the cells, and progression resistance because of larger current transport distances.

    Furthermore, in practice, solar modules never operate under conditions equal to the measure test conditions (STC). The solar spectrum and intensity change during the day and vary with the time of year. The dependence of efficiency on incident power is generally lowest for cells with towering FF. Here the high-efficiency (mono)crystalline materials as well as thin-film CIGS and CdTe (all with FF > 0.79) gain an edge over perovskites and the lower-efficiency thin-film materials (FF < 0.73). Also, solar modules heat up under solar irradiation, sometimes reducing the efficiency by 1 to 2% (absolute) relative to their STC value defined at 25°C. The temperature coefficient of efficiency depends strongly on material and is lower for Si heterojunction cells, CdTe, and CIGS than for other materials (38, 39). Another dissimilarity between practical, tolerable module efficiency and STC efficiency is related to the fact that in rehearse modules receive light from a wide gain of angles rather than perpendicularly incident light only. This leads to additional reflection losses. Finally, they note that nearly barnone cell/module combinations expose reduction in efficiency over time. This is attributable to factors including degradation of the cells, oxidation of metallic cell interconnects, and photodegradation of polymer encapsulating layers; the magnitude of these effects depends on the cell/module combination (40). Understanding these degradation mechanisms in different climates is a involved but very principal research challenge.

    On the basis of their partake in the market for PV systems, which had an estimated value of $96 billion in 2013 (1), it can subsist said that monocrystalline Si, multicrystalline Si, CdTe, and CIGS gain evolved into develope high-efficiency technologies, with Si technology having >90% of the market share. Record efficiencies for large-area (>800 cm2) modules are 22.4% for monocrystalline Si (9, 41), 18.5% for multicrystalline Si (9), 18.6% for CdTe, and 17.5% for CIGS (9, 42). These materials barnone belong to the >75% S-Q confine (for monocrystalline Si) or 50 to 75% S-Q confine (for multicrystalline Si, CIGS, CdTe) classes in Fig. 1B, directly demonstrating the significance of efficiency as a lever for large-scale application.

    A recent evolution is the demonstration of single-junction GaAs solar modules with a record efficiency of 24.1% that are fabricated on an industrial scale and are now on their course to commercial exploitation (43). It will subsist quick-witted to discern how the manufacturing costs for each of the >20% module technologies will subside in the coming years. Thin-film solar cells deposited on thin foils are too expected to find current applications in areas where low weight-specific power (in terms of watts per gram) is desired, and in novel forms of building-integrated PV where resilient shape factors or partial transparency for visible light are desired.

    Thin-film amorphous and crystalline Si modules and resilient foils gain too been developed to a commercial even but are applied on a much smaller scale because of their lower efficiency (12.2% for a module based on a tandem geometry) and higher manufacturing costs (44). Furthermore, small-area modules of dye-sensitized solar cells (efficiency 10.0%) (45, 46) and organic solar cells (9.5%) (30) are commercially available but thus far picture a tiny market. Thin-film perovskite, CZTS, and quantum dot solar cells gain been demonstrated in the lab, but modules gain not yet been demonstrated on an industrial scale. For perovskites, long-term stability and manufacturability gain not yet been demonstrated; for CZTS and quantum dot solar cells, the low efficiency limits commercial development. Table 1 summarizes technological strengths and selected research technology opportunities for barnone reviewed materials.

    Table 1 Technology strengths and key research opportunities for photovoltaic materials.

    Materials are grouped by degree of technological development. Record cell and module efficiencies are indicated, based on certified measurements. GaInP and InP are not included as no significant evolution toward commercial technology exists; n.a., not available.



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