T his Photovoltaic Program Five-Year Planis being published today, January 1,2000. It is the first day of a new century

that will eventually be powered by renewableenergy technologies like photovoltaics (PV).

In the PV community, there is a sense of excite-ment and challenge — the same feeling mem-bers of the Apollo program must have felt atthe start of the moon race. In 1999, we cele-brated the 30th anniversary of Apollo 11'ssuccessful mission. A little more than a yearago, the Mars Sojourner Rover, entirely poweredby PV, completed its mission. The challenge weface in this century is to enable PV to go as faras any other energy technology here on Earthby making the scientific and technologicaladvances that will put PV on every rooftop andin every corner of the globe. Like the spaceprogram, a balanced, aggressive PV researchand development program has the potential toopen a new frontier here on Earth.

When John F. Kennedy challenged the nationto put a man on the moon within a decade,the scientists who would lead the effort hadlittle more than a mission from their Presidentto guide them. But that was enough toinspire them to the hard work and dedicationit took to create a plan, a program, and finally,the technology that would open a new fron-tier in space. Our mission is alsobold and inspiring —

to offer the world a cost-effective, reliabletechnology that turns sunlight into energywith no pollution, wherever it is needed.

Apollo’s scientists, engineers, and astronautspursued their mission with perseverance, inge-nuity, and scientific curiosity and in the processchanged the way we view our planet and ourfuture. They were the first to capture the view,featured on the cover of this five-year plan, ofthe Earth as a lone planet surrounded by thevastness of space. For many, it signified the lim-its of the Earth and our resources, and theoverriding need to protect our environment.For others, the fact that science and technologyhad allowed people to leave Earth and lookback on our planet from the moon signified theability of science and technology to overcomeall limitations. The entrepreneurs, scientists, andengineers that make up the PV communityrepresent the best of both views — a beliefthat science and technology, guided by pur-pose and vision, can overcome all limitationsand tap new energy resources that also protectour global environment.

The PV industry has created a new technologyroadmap to chart industry’s course. This five-year plan provides a strategy for research and

Taking Steps Toward a New Energy Front

Taking Steps Towarda New Energy Frontier . . . . . . .2

Photovoltaics — Energy for the New Millennium . . . . . . . . .4

• The Promise of Photovoltaics• A National Endeavor

• Guiding the Effort

The Research Program —Delivering the Promise . . . . . .10

• Research and Development• Technology Development

• Systems Engineering & Applications

2

development to advance the technology.Considering just the opportunities that we canforesee from where we stand today, at thestart of the century and with a new five-yearplan, PV has enormous untapped potential.

Early in the new century, highly efficient PVcells will power the exploding market intelecommunications. New technologies will linkautomobiles to satellites and the Internet forcommunications, information, location anddirections, tracking, and even video on demandfor the backseat — all of which will rely ondirect-current electricity coming from PV inte-grated into the car roof or hood.

As the use of personal computers, digital cellularphones, and other portable electronic devicesflourishes, more of the appliances we value mostwill be powered by batteries and encased in PVmaterials so they can recharge themselves — theultimate wireless convenience.

As the next century rolls on, we will see PVsystems grace millions of American homes.We’ll see a proliferation of PV systems builtonto the rooftops of factories and businesses,or integrated directly into the “skin” of houses,skyscrapers, and commercial buildings to pro-vide supplemental or stand-alone power. And

we’ll see the emergence

of “PV farms” that range in size from a fewacres to square miles of PV systems, to provideelectricity for entire communities or for entireregions of the nation.

We’ll also witness the growing impact that PVwill have in developing countries, home to the40 percent of the world’s population that hasno access to electricity. Modules on therooftops of houses and huts will provide fami-lies with electricity for light and other essentials.Ground-mounted arrays will provide power forpumping water for drinking and irrigation.Moderate-size systems will supply entire villageswith power to run lights, communication, andsmall industries, and will supply health clinicswith power for operations and for refrigeratingmedicines. Photovoltaics and satellite telecom-munications will open remote villages to worldcommerce, education, and virtual medicine. Allof this will happen without building powerlines or telephone poles.

The new energy frontier that PV will helpopen is vast. Opening it will take manysmall, meticulous steps, like those outlinedin this five-year plan. In research and devel-opment, we often fail to appreciate theimplications of the steps that are takenevery day to advance a program’s mission.Sometime early in this new century, we willtake one of those small steps for photo-

voltaics and suddenly realize we haveaccomplished our own giant

leap for mankind.

ier

ServingAmerica . . . . . . . . . . . . . . . . .18

Five-Year PV Program TechnicalAreas and Milestones . . . . . . .18

Industry Roadmap2000–2020 . . . . . . . . . . .end flap

3

James E. RannelsDirector, Office ofSolar Energy Technologies

A t the dawn of the new millennium, the worldfaces dramatic change. Nations are expandingtheir economies. Growing populations spawn

spiraling needs for food, shelter, and materials.Burgeoning demands burden the Earth's ecosystems.

Underlying these trends is the expanding demand forenergy. In the last 20 years, the world has increasedits consumption of energy by 40%, to more than390 quads of energy per year. More than 85% of thiscomes from fossil fuels. Although fossil fuels have longdriven the engines of economic growth, consequencesof their use are becoming apparent — limited supplies(in the long term), air pollution, and an increase inatmospheric carbon dioxide.

But nations can continue their economic ascent andincrease their energy consumption while becomingmore harmonious with the environment and whileensuring sufficient supplies of energy. Key to the successof this vision is technology and its ability to provide theworld with a wide portfolio of energy choices.Significant among these is photovoltaics, a semicon-

ductor technology that converts sunlight directlyinto electricity.

The Photovoltaics Program is helpingto turn the promise of PV into a

reality. The partners of the pro-gram — the National

Renewable EnergyLaboratory (NREL),

Sandia NationalLaboratories, the

U.S. Departmentof Energy

(DOE), andthe

nation’s universities and PV indus-try — explore the interaction of PVmaterials with sunlight, synthesizematerials to exploit the interaction,model devices, engineer sys-tems, and develop technolo-gies that will help the nationand the world make the transi-tion from today's fossil fuel real-ity to a sustainable, clean, andprosperous world.

The Promise ofPhotovoltaics Good for Our Nation'sEnergy Supply

PV is a versatile electricity technol-ogy that can be used for any appli-cation, from the very small to thevery large. A modular technology that enables electricgenerating systems to be built incrementally to matchgrowing demands. A technology in which systems areeasy to install, maintain, and use. A convenient tech-nology that can be used anywhere there is sunshineand that can be mounted on almost any surface.

PV gives us domestic reserves of energy that we willnever deplete. PV semiconductor materials are abun-dant. And sunshine, the “fuel” for PV, is something wecan never overtax or squander. Yearly, the Earthreceives 6000 times more sunlight energy thanhumans consume.

Moreover, because sunshine is available everywhere toeveryone, any nation that builds a PV infrastructurewill be less vulnerable to international energy politicsand volatile fossil fuel markets.

Good for Our Economy

In 1998, worldwide PV module shipments jumpedto more than 150 million watts, resulting in about$1.5 billion in sales. When the PV Program firstbegan in the 1970s, there was no market forterrestrial photovoltaics. The market since thattime has grown steadily. And in the last fiveyears, it has grown at an annual rate of 20%.

This is just the beginning. The Program andindustry feel that a sustained growth rateof 25% is achievable. At such a growthrate, worldwide shipments wouldapproach 18 billion watts per year by

Photovoltaics — Energy for the New Mill

Photovoltaicspromises greatthings for our

nation's energysupply, economy,

environment...and future.

4

ennium

5

2020, representing a direct PV market of about$27 billion and an indirect market double that. AndU.S. PV shipments would reach 7 billion watts by 2020,with more than 3 billion watts for domestic use. Thismeans that PV would be supplying about 15% ofAmerica’s added generation capacity.

A large, growing market bodes well for Americanworkers. According to some estimates, the PV industrycreates more than 3000 direct and indirect jobs forevery $100 million in direct module sales. As thisindustry grows toward its potential, it will generatehundreds of thousands of jobs.

The race for technology and market leadership, how-ever, will be hard fought. Although PV technology isAmerican born and bred, and although the UnitedStates has long been the technological leader, anynation that makes the commitment can build a PVindustry. Those that do will create domestic jobs,export energy technology, keep energy dollars athome for further domestic investment, and reap theancillary economic benefits of controlling a technologywhose impact will reach well beyond energy.

Good for Our Environment

PV produces no greenhouse gases, so its use will helpoffset carbon dioxide emissions. Consequently, build-ing a PV infrastructure will provide insurance againstglobal warming and climate change. A 4-kilowatt(kW) system, for example, will supply the electricity fora typical U.S. home; furthermore, the annual amount

of carbon dioxide saved by the system is approximatelyequal to that emitted by a typical family car.

PV also produces no atmospheric emissions. Its usecurtails air pollution, which produces acid rain, soildamage, plant and animal damage, and human res-piratory ailments.

Good for Our Future

Photovoltaics is sophisticated science and high tech-nology — an open-ended technology in which there isyet much to discover and much to reap. It will have animportant impact on technologies ranging from com-puters, to thin-film transistors, to uninterruptible powersupplies, to space power and the increasingly impor-tant field of telecommunications.

As such, PV will be an integral part of the march oftechnology that will spur economies and promote amore cohesive and affluent world.

Photovoltaics will help create a more prosperousworld because it can be used by anyone, anywhere,for any application requiring electricity. It will promotea more equitable world because the resource is hugeand universal, and because the technology can beused by everybody.

But the promise of PV goes well beyond electricity.Photovoltaics is a versatile technology that can beintegrated with electrochromic windows, to help con-serve energy while providing electricity. It can alsobe used to electrolyzehydrogen from water;the hydrogen can thenbe used to produceelectricity, heat ourbuildings, and run ourtransportation. Electricity,conservation, and hydro-gen from PV and the sun— inexhaustible, clean, andfor everyone.

Whether the PV markets continue to grow at their historical rate (from 15% to 20%) or at an accelerated rate of 25%, PV will provide the nation with alarge amount of electricity by 2020.

A bright future atour fingertips —hydrogen from

sunlight, water,and PV electricity.

Electricity, fuel,and heat —

inexhaustible and clean.

A National Endeavor The purpose of the U.S. Department of EnergyPV Program is twofold: to accelerate the developmentof PV as a national and global energy option, and toensure U.S. technology and global market leadership.

Building Technology Leadership

Technological leadership is essential to U.S. industrialcompetitiveness in photovoltaics. Although PV is fastbecoming a multibillion-dollar industry, to become asignificant energy player, it must extend itsinfluence into more and larger mar-kets. To do this, costs must bedecreased by addressing keytechnical issues, including:

• Making dependable PVdevices that convert sunlightto electricity efficiently

• Developing low-cost, high-yield processes formanufacturing PV modules

• Developing a strong scientific base to ensure thecontinued technical progress that will enable PVcost to become competitive for large, price-sensitive energy markets.

Working with the U.S. PV Community

To address technical issues, the DOE PV Program fol-lows a well-established national paradigm — the form-ing of partnerships among national laboratories, indus-try, and universities — that has built U.S. leadership in

many important technolo-gies, including integratedcircuitry, computers, andbiotechnology.

In its version of the para-digm, the Program hashelped build a nationaleffort, supporting partner-ships that span the range

from basic and applied research, to manufacturing tech-nology, to product development, to commercialization.The work is performed by the National Center forPhotovoltaics (NCPV) and other associated research cen-ters at the National Renewable Energy Laboratory,Sandia National Laboratories, and Brookhaven NationalLaboratory, and by more than 180 leading companies,universities, and utilities from 40 states across the nation.

Companies compete for contracts and share in theircosts. They then integrate results of successfulresearch with their own considerable in-house effortsand apply them to manufacturing processes andproducts. Industry generally provides a supportingrole for basic and applied research and development

(R&D); but when thetechnologies approach

manufacturing and com-mercialization, industry

assumes the lead.

Working closely with thenational laboratories and

companies, universities performadvanced R&D, explore funda-

mental scientific phenomena, createinnovative concepts, and provide a fertile learningground for tomorrow's PV scientists and engineers.

The national laboratories of the NCPV — NREL,Sandia, and Brookhaven — provide the PV communitywith program management and centralized technicalsupport, characterize PV materials and devices, per-form research on fundamental concepts, and conductinnovative research on materials, devices, and process-ing. The laboratories generally take a lead role in theearly stages of a technology’s development, butassume a more facilitating role as the technologyapproaches commercialization.

Paying Off

When the PV Program began in the early 1970s,there were no markets for terrestrial applica-tions. But R&D and innovation havedropped costs more than 100-fold andhave enabled PV to enter more andlarger markets. Today, PV systems gracea quarter of a million American homes,and the industry is arching towardmultibillion-dollar markets and produc-tion capacities of hundreds of millionsof watts per year.

In the early days, the DOE Program supportedmainly crystalline silicon technologies. Asa result, the technologies progressedsignificantly, with constantly improvedmanufacturing capabilities, grow-ing device efficiencies, greaterreliability, and longer modulelifetimes. Today, these arethe dominant PVtechnologies.

The PV Program workswith the nation’s PVcommunity to build

technology leadershipthat is paying off.

6

But other PV materials — most notably, thin-film amor-phous silicon — are grabbing market share. And productsmade of the thin-film materials of copper indium di-selenide and cadmium telluride are also being introduced.

The commercialization of copper indium diselenide,cadmium telluride, and (earlier) amorphous silicon areparticular success stories of Program partnerships. Itwas the Program that performed the initial R&D onthese materials and nurtured the technologies to thepoint where they could begin to be commercialized.

The same is true with multijunction high-efficiencydevices made from gallium arsenide and its alloys. TheProgram and its partners have brought these technolo-gies to where companies are now introducing them tomarkets as varied as space, concentrator, and thermo-photovoltaic applications (in which PV systems exploitinfrared radiation from heat to produce electricity).

An Even More Promising Future

Crystalline silicon technologies are beginning to entera new era, in which structures that increase sunlightabsorption will enable crystalline cells to be made withvery thin layers. This will cut device costs while increas-ing conversion efficiencies.

New approaches for thin-film technologies are pushingconversion efficiencies nearly as high as those of crys-talline silicon. By continuing this trend and consolidat-ing improvements, thin films will substantially lowerthe cost of PV electricity to where PV will be able tocompete for large markets.

Companies are developing manufacturing technologiesfor thin-film photovoltaics that will produce 50 to 100million watts of modules on a single production line

yearly. Such economies of scale will also greatly

lower costs. Because of the progress made by scien-tists under the sponsorship of the Program and ofDOE’s Office of Basic Energy Sciences,researchers can now controlimportantproper-ties ofthe gal-liumarsenidefamily of mate-rials. This is leading tothe ability to make multilayer devicesthat will eventually achieve conversion efficiencies of40% or more. An extension of this work has led toimportant inroads in developing simple systems thatefficiently split water into hydrogen and oxygen,which has implications for fuel cells and clean powerfor the nation's industries and transportation.

And, looking into the needs of the future, theProgram is working with its university partners, theCenter for Basic Sciences at NREL, and others toexplore futuristic concepts that may someday sup-plant even today's most advanced and sophisticatedtechnologies. Among the ideas being investigatedare PV devices that do not need the junction thathas heretofore been necessary to separate chargecarriers, and PV systems that mimic biological sun-light-to-electricity conversion.

By working with the U.S. PV community, the PVProgram is paying off today, and will pay off in a bigway in the future. Photovoltaics is a fast-paced semi-conductor technology with the potential to becomeone of the world's most important industries. Toreach that potential, the Program and its partners willcontinue to address scientific and technical chal-

lenges using the complementary strengths of thepublic and private sectors.More than 180 universities,

companies, and utilities from acrossthe United States take part in thenational photovoltaic endeavor.

UniversitiesCompanies

UtilitiesDOE HQ, NREL, Sandia

7

Working withthe Program, theU.S. PV industryhas greatlyincreased itsmanufacturingefficiency andcapacity andhas substantiallydecreased thecost of modules.

Guiding the EffortSomething as crucial to the nation’s well-being as ener-gy R&D requires national guidance — a federally coor-dinated effort that relies on national policies, a nationalorganization, national strategies, and national funding.

Establishing Policies

Reflecting the recommendations of the Chief Executiveand national energy advisory boards, the Secretary ofEnergy develops overarching federal energy policiesthat guide the DOE PV Program. The Secretary also

develops a national energystrategy with broad nationalgoals for R&D that promote:

• Energy system efficiencyand increased economicproductivity

• Energy security for thenation

• Environmental quality andhealth

• Future energy choices for Americans

• Solutions to international global issues.

Managers of the PV Program develop operating plansthat respond to national policies and goals, toCongress, and to the Program’s constituents. The man-agers also ensure that the budget allocations, direc-tion, and individual elements of the Program meettheir objectives and stay on target.

Organizing the National Program

DOE’s Office of Energy Efficiency and RenewableEnergy (EERE) oversees the PV Program through itsOffice of Solar Energy Technologies. To ensure that thenational photovoltaiceffort meets itspromise in anefficient andtimely manner,the PV

Program is organized to effectively usher technologiesalong the development path from basic R&D, throughapplied research, through technology develop-ment, to engineering and appli-cations. These efforts are aug-mented by the Office of BasicEnergy Sciences, which providessubstantial support for basic R&Din several areas of PV technology.

To mobilize national resources inphotovoltaics, the PV Programrecently established the NationalCenter for Photovoltaics at its twoprimary research centers: theNational Renewable EnergyLaboratory in Golden, Colorado,and Sandia National Laboratoriesin Albuquerque, New Mexico.The Center performs world-classR&D, promotes partnering andgrowth opportunities, and servesas a forum and informationsource for the PV community.

NREL and Sandia not only serve as core members ofthe NCPV; they are also responsible for the day-to-dayoperations of the Program and for meeting theProgram’s technical goals. Staff members at these labsperform R&D, form R&D partnerships with universitiesand industry, and manage subcontracts.

Other NCPV members also have Program responsibili-ties. For example, Brookhaven National Laboratory inUpton, New York, is responsible for the Program’s envi-ronmental, safety, and health research. DOE’s GoldenField Office administers contracts with the private sec-tor in some program areas. The University Centers ofExcellence at the Institute of Energy Conversion(University of Delaware) and at the Georgia Institute ofTechnology support the industry and the R&D infra-structure with research to advance thin-film and crys-talline silicon technologies. And the Florida SolarEnergy Center and the Southwest TechnologyDevelopment Institute are regional experiment stationsthat test modules and systems under different environ-ments and field conditions.

Strategies, Schedules, and Plans

"The Plan is nothing. Planning is everything."– Winston Churchill

Although meant for the process of planning war-timestrategy, this saying is also germane for planning andexecuting R&D. It is through the planning process thatthe Program sets the wheels in motion toward impor-tant goals and milestones. The Program then revisitsand revises plans in accordance with progress, growth,competition, and emerging priorities.

In simple terms, PV planning consists of three cycles:long-range, mid-range, and short-range. Long-rangeplanning is done by industry with a planning horizon

Through policies,organization, strategies,

and funding, the PVProgram coordinatesthe nation's R&D for

photovoltaics.

8

of 20 years. The NCPV provides a forum for this plan-ning and facilitates its process. Industry’s primary con-cerns are goals for growth and markets and theprocesses, equipment, systems, and R&D it will needto meet these goals.

The Program’s approach to planning not only encom-passes American industry’s long-term agenda for tech-nological and industrial preeminence, but also heedsthe national agendas for economic growth, energysecurity, and environmental quality and health.

The Program’s principal planning cycle has a five-yearhorizon. This effort is performed under the guidanceof the Director of the Office of Solar EnergyTechnologies. Planning is coordinated by the NCPVand involves project leaders and managers from NRELand Sandia, and program managersfrom the DOE in Washington, DC, andthe Golden Field Office.

The planners determine the direction forthe Program, set five-year goals for eachof 10 major project areas in three R&Dcategories, establish annual or biannualmilestones for each of those areas, anddevise strategies for meeting milestonesand goals. The plan then is sent out tothe entire PV community for review. Thepublished plan serves as a guide for allthe participants in the DOE PV Program.

Although this is a five-year plan, it is scheduled forrevision every two years in accordance with newprogress, a new five-year horizon, and new require-ments and funding.

Short-term planning is done on an annual basis in anAnnual Operating Plan. Program managers and projectleaders detail the R&D, facilities, equipment, expertise,and progress needed to reach the milestones stipulatedin the five-year plan. The NCPV coordinates this plan-ning to make sure that participants are heading towardthe correct goals, to pare redundancy, and to ensurethat the Program efficiently performs its R&D mission.

Funding the Program

Congress provided $72.2 million for photovoltaics infiscal year (FY) 1999. (An additional $2.8 million wasallocated to the Office of Basic Energy Sciences foruse in basic R&D on PV sciences and technologies.)With an eye on how best to achieve its strategicgoals, the Program distributed this funding amongthe Program’s major elements and participants.

Federal support for the PV Program is more thanmatched by industry. The private sector outspends thegovernment PV R&D by more than a factor of two —by typically paying for at least 50% of the costs ofshared R&D projects, by pursuing their own R&D, andby developing manufacturing facilities.

More than 70 U.S. companies participate in the pro-gram. By doing so, they and the government leveragefunds and expertise, accelerating the technologytoward the goals of indus-try and of the nation.

These collaborations withindustry and academia arespurring PV to its incredi-ble promise of taking thenation along the high-tech highway toward itsenergy, economic, andenvironmental futurein a sustainable andclean manner.

9

For FY 1999, the Program splitits $72.2 million budget among its three pro-gram elements in this manner: $33.6 million (47%)to Research & Development, $18.9 million (26%)to Technology Development, and $19.7 million(27%) to Systems Engineering & Applications.

1995 2000 2005 2020–2030

Module efficiency* (%) 7–17 8–18 10–20 15–25

System cost ($/W) 7–15 5–12 4–8 1–1.50

System lifetime (yrs) 10–20 >20 >25 >30

U.S. cumulative sales (MW) 175 500 1000–1500 >50,000

*Range of efficiencies for commercial flat-plate and concentrator modules

Relying on past progress and prognoses for further technological progress, theProgram sets general mid- and long-term goals (costs given in 1999 dollars).

10

Photovoltaicshas come along way since

the DOE PVProgram beganmore than twodecades ago.We have seena profusion of

technologies —new materials,

new device con-cepts, and new

growth techniques and man-ufacturing processes. We have seen efficiencies riseconsistently, module lifetimes increase beyond 20 years,and costs plummet more than 100 fold.

And we have witnessed a fledgling industry strength-en and grow, producing new products for new appli-cations, and penetrating new markets.

Yet, there is much to be done. To deliver PV’s promisefor the new millennium, we must reduce its cost, makeit more competitive for more applications, make

devices more efficient andreliable, and make systemsthat last longer.

To accomplish these aims,we have crafted a programin which we explore awide portfolio of concepts,materials, and technol-ogies; a program thatsteers the technologiesfrom seminal idea, throughbasic and applied research,through engineering, to

commercial readiness. This program involves threemajor elements — research and development, technol-ogy development, and systems engineering and appli-cations — each of which is guided by technical goals.

Research & DevelopmentIn this area, scientists conduct basic research onpromising new materials, processes, devices, and pro-duction techniques. This includes research in thinfilms, high-performance concepts, crystalline silicon,characterization techniques, and basic research onunconventional ideas.

Thin Films

Imagine making PV absorbers less than 1 micrometerthick on long, thin, flexible sheets. Or mass producingsquare miles per year of inexpensive, efficient PV mod-ules. Such is the motivation behind the Program'sresearch on thin-film PV materials.

Thin films represent a success story. In the late 1970s,the Program began research on what were then “non-conventional” thin-film materials. For those materialsthat showed promise, the Program cooperated withindustry and universities to further develop the tech-nologies. Today, these materials — amorphous silicon(a-Si), cadmium telluride (CdTe), copper indium dise-lenide (CIS), and thin-film silicon — are among theleading candidates for low-cost photovoltaics.

A success story in progress is the cooperation that istaking place under the Thin Film PV Partnership. Eachthin-film technology has formed a national team com-prising the nation’s best research and engineering talentdrawn from industry, universities, and the nationallabs. Together, the teams are overcoming technicalbarriers and are accelerating the state of the art.

Amorphous silicon. This was the first thin-film materialto go commercial. Initially, a-Si was used mostly in con-sumer items such as calculators. With increasingefficiencies, proven manufacturability, and innovativeproducts such as modules that double as roof shingles,a-Si is rapidly expanding its markets.

The primary challenge is to raise the stabilized conver-sion efficiencies for a-Si devices, which lose efficiency

To deliver the PVpromise of plentiful

clean, versatile, low-cost, high-tech energy,the Program explores

a wide portfolio oftechnologies.

The Research Program — Delivering the The Research Program — Delivering the

Since the inception of the Program's R&D on thin filmof cells have risen steadily, reaching today’s highs o15.8% for CdTe cells, and greater than 12% for a-Si

P

11

when first exposed to light. The national a-Si researchteam is pursuing the challenge by investigating degra-dation mechanisms that cause this initial loss of effi-ciency and by exploring innovative designs to increaseefficiencies. The team has already made progress, withthe best stabilized efficiencies to date around 12% and10% for cells and modules, respectively. The goal is toproduce a stable 15%-efficient device.

Copper indium diselenide. After two decades ofR&D, CIS has been introduced to the market, withmodules consistently reaching stable efficienciesgreater than 11% — beating the goal set in the lastfive-year plan by more than a year.

CIS is also enjoying success in the lab, with cell effi-ciencies climbing to a world-record 18.8% (nearly ashigh as that of polycrystalline silicon cells). Thisprogress bodes well for meeting the year 2001 cell-efficiency goal of 20%.

Researchers are investigating ways in which to pushefficiencies even higher, by exploring the chemistryand physics of the junction formation, and by examin-ing concepts to allow more of the high-energy part ofthe solar spectrum to reach the absorber layer.

They are also trying to drop costs and facilitate thetransition to the commercial stage by increasing theyield of CIS modules (i.e., by increasing the percent-age of modules and cells that make it intact throughthe manufacturing process).

Cadmium telluride. With more than 50,000 watts ofmodules being field tested, CdTe is on the verge of

going commercial. Thismaterial is consideredpromising largely becauseit can be made using low-cost techniques, such aselectrodeposition andhigh-rate evaporation.Using a variation on thislast method, one companyis obtaining a throughputrate of one large moduleevery 30 seconds. This ap-proach could be geared upto produce 100 megawattsof modules per year, whichwould considerably dropthe cost of PV electricity.

Prototype CdTe modulesare reaching efficienciesbeyond 9%, while labora-tory cells are approaching16%. Researchers on theCdTe team are trying toboost efficiencies by,

among other things,exploring innovativetransparent conduct-ing oxides that letmore light into thecell to be absorbedand that more efficient-ly collect the currentgenerated by the cell.

Some CdTe devices, how-ever, appear to exhibitsome degradation at thecontacts. Understandingthe degradation andredesigning devices tominimize it will be majorefforts of the Program dur-ing the next few years.

Thin-film silicon. This approach combines the lowcost of thin films with the high efficiency of crys-talline silicon by using innovative designs thatemploy low-cost substrates, porous polycrystallinesilicon, and techniques that trap light in silicon fortotal absorption. This allows the use of silicon layersas thin as 10 micrometers (20 to 30 times thinnerthan traditional crystalline silicon) while getting highefficiencies. Although this approach is relatively new,the Program is already making working modules.

High Performance

Consider a 40%-efficient cell 2.5 centimeters in diame-ter. Under a normal sun in the southwest UnitedStates, it could produce about 0.2 watt of power.Now consider concentrating the sun 1000 times onjust 100 of these cells — it would produce 20,000watts! That is the attraction of high-performance cells:using small, highly efficient cells with inexpensive con-centrators produces large amounts of low-cost power.

This avenue of research represents another Program tri-umph. Researchers have gained a deep understandinginto the microscopic order of gallium arsenide alloys,allowing them to control the growth parameters of thealloys and “tune” their band gaps. This enables them toroutinely make 2-junction devices (which employ twocells with different band gaps grown one on the other,to capture a larger portion of the solar spectrum) thatobtain efficiencies greater than 30%.

This technology is now being used by industry tomake cells that power satellites. Although this hasgreat potential for satellite power and telecommunica-tions, it has greater potential for power on Earth. Andit is already leading to 3- and 4-junction cells thatpromise 40% efficiency, which could double the effi-ciency of current commercial concentrator systems.

NREL scientistshave pioneered thecapability of tuningband gaps of III-Vmaterials, by precisely controllingtemperature andgrowth parameters. Such a capability isleading to thedesign of 3- and 4-junction high-efficiency cells.

PromisePromise

ms, conversion efficienciesof 18.8% for CIS cells,i cells.

This approach can also be applied to polycrystallinethin-film materials to get the best of both worlds: lowcost with high efficiency. By first optimizing singlejunction concepts, and then tuning band gaps andmonolithically (i.e., one on top of the other) growing2- and 3-junction polycrystalline, thin-film devices, wemay be able to double the efficiencies of today’s thin-film modules. This could nearly halve the cost of thin-film PV electricity.

Crystalline Silicon

Crystalline silicon (c-Si) has a well-established technologybase and the c-Si industry controls nearly 90% of the PVmarket. It should continue to dominate the market for atleast five more years. The technical progress will be evo-lutionary, but the advances will be quickly integrated into

the marketplace. Thiswill help build theinfrastructurerequired for contin-ued rapid growth.The Program is push-ing technologicaladvancement in twoways: throughresearch on materialsand research onprocess and devices.

Materials. The concept is simple: improve the startingmaterial and your knowledge about it, and you'llimprove devices made with the material. To this end,

researchers are investigating the fundamentals ofimpurities and defects in crystalline silicon —

their effects and their evolution dur-ing different types of process-

ing steps. As an example,researchers are explor-

ing a method widelyused in the

computerindustry

(“gettering”) to remove impuri-ties from crystalline siliconusing heat treatments. Suchmethods along with funda-mental understanding mayallow the use of less purematerials, which can reducethe cost and increas the avail-ability of startingmaterial.

Process and devices. Anothersimple concept: improve pro-cessing and innovative devicestructures, and you‘ll increaseefficiencies while decreasing fabrication costs. Forexample, expensive laboratory cells have achieved effi-ciencies as high as 24.7%, whereas commercially pro-duced cells typically have efficiencies less than 16%.The trick is to develop fabrication processes and devicestructures that can translate some of the performancefeatures of laboratory cells into manufacturing. To mas-ter this trick, researchers are exploring highly versatiletechniques — such as plasma processing, which canetch surfaces, deposit dielectric coatings, and passivatesurface and bulk defects — to form high-efficiency cellstructures using manufacturing procedures.

A second thrust of c-Si research is to develop newprocesses that require less energy, material, and laborthan conventional approaches and that will result ingreater throughput. The goal is to double the outputof a manufacturing plant without increasing its size;this will help industry reduce manufacturing costswhile increasing output. One research approach thatcould help reach this goal is rapid thermal process-ing, a low-cost method that uses high-intensity lightto rapidly heat substrates and optically enhance pro-cessing steps.

Finally, researchers are investigating radically newdevice structures that have the potential to significant-ly reduce the cost of cells and modules. Although theProgram and its partners have continually reducedcosts, it has been done largely through constantrefinement in manufacturing processes. The basicdesign of crystalline silicon devices has remainedessentially the same for 20 years. New approachesthat are based on cells and modules specificallydesigned for easy manufacturability will considerablysimplify the assembly of PV modules and reduce costs.

Measurements and Characterization

To make a device that works well is not enough. Tooptimize the device or to push the concept beyond itspresent confines requires knowing the doping profile,

R&D on thin films, high-performance devices, silicon

materials, characterizationtechniques, and innovative

concepts will deliver low-costPV and fill the technology

pipeline for future progress.

An early candidate for in-line diagnostics is thisNREL-developed technique — radio-frequency photo-conductive decay. It quickly and easily measures theminority-carrier lifetimes of wafer material, an impor-tant characteristic indicative of material quality.

12

morphology, short-range order, stoichiometry, perfor-mance characteristics, and more.

Such knowledge is garnered using measurement andcharacterization capabilities that span more than tenorders of magnitude — from atoms to arrays — and thatprecisely determine microscopic and macroscopic proper-ties of a material, device, or process. Once we know theproperties, we are in a position to push the technology.

This area of research cuts across all strata of theProgram, from basic R&D to module and system per-formance. Researchers also work with the nationaland international PV communities to set standards sothat devices and systems can be fairly and adequatelymeasured and compared.

And now, the Program is extending its analytical services.Together with the PV community, the Program is definingthe needs of manufacturers for diagnostic tools. In accor-dance with these needs, the Program will develop tech-niques and tools for in-situ diagnostics and smart process-ing. These will include tools that can be inserted intogrowth chambers to analyze growth parameters, and toolsthat can be incorporated into processing lines to analyzewafer and device quality. Such tools will help manufactur-ers make better products, with better material utilization,and greater manufacturing yield and throughput.

Basic Research

Where do innovative ideas come from? Ideas that allowyou to meet or beat cost and performance goals? Ideasthat help reinvigorate the Program? Many of themcome from the Program’s own researchers, or fromresearchers supported by related areas (such as theOffice of Basic Energy Sciences), and from universities

across the nation. The Program funds promising con-cepts, eventually winnowing out those that do notcome to fruition and backing those that continue toflourish. Some of these become Program triumphs.

Recently, the pipeline of innovation was refilled withconcepts whose success could eradicate remainingbarriers to our goals or could take us well beyond tothe next generation of technologies.

To tap the latest ideas for innovation, the Programheld a conference on future-generation technologiesand funded some of the most promising concepts. Italso solicited unconventional ideas from the nation’suniversities, funding 18 of the proposals.

Among the ideas being explored under this project are:

• High-efficiency devices that use III-V nitride alloysand various growth methods to make 3- and4-junction cells. The nitride alloys can be used tolower band gaps, enabling the cells to efficientlyconvert the red end of the spectrum.

• Quantum dot solar cells, in which semiconductorabsorbers are grown at nanoscale sizes and embed-ded in a polymer/C60 composite. This uses quan-tum confinement for controlling band gaps. It alsopromotes the rapid transfer of charge carriersacross the nanocrystal/composite interface, whichmimics one part of the photosynthetic process.

• Dye-sensitized photochemical cells, which usenanocrystalline titanium oxide (TiO2 — the cheapwhite pigment in most paints and in toothpaste)to convert sunlight to electricity, and inexpensivedyes to make TiO2 sensitive to a broader range ofthe solar spectrum. When used with an elec-trolyte, this system generates electricity throughelectron and hole transfer to electrodes.

From this work may arise technologies thatrequire no p/n junction, that can pro-duce “square miles” of cheap buthigh-quality PV material, andthat give us new insight intomaterial properties.

Cell performance can be improved by gettering,which removes impurities. Once a cell has beengettered (right), its photoresponse is better thanbefore (left). A higher photoresponse (denoted bygoing from pink to green and from green to red)indicates a greater generation of charge carriersthat can be collected by the grid.

One of the innovativeconcepts being exploredfor future-generation PV is a device that usesnanocrystals of CdSe embedded in a polymer/C60composite for electron-hole trans-fer. This concept has the potential forlow-cost, large-area fabrication.

13

TechnologyDevelopmentIn its roadmap, the U.S. PV industry set its long-termgoals — 40% of the world PV market with annualsales of 7 billion watts and domestic sales of 3.2 bil-lion watts by 2020. Reaching these goals will require

the industry toincrease manufac-turing capacity bynearly 100 fold anddomestic sales byeven more.

This calls for strenu-ous efforts. It callsfor translating R&Dadvances in materi-

als, devices, and processes to the manufacture ofproducts. It calls for decreasing costs to capture widermarkets. It calls for increasing the reliability of mod-ules, components, and systems so that they lastlonger and perform better throughout their lifetime.

And it calls for close cooperation between the PV indus-try and the Program, to leverage expertise, facilities, andfunds and to accelerate the development of technology.

Manufacturing R&D

R&D partnerships. Since the early 1990s, theProgram and the PV industry have worked assidu-ously to push the state of the art in manu-facturing technology. This hasbeen a model of coopera-tion in whichthe

Program has formed a series of R&D partnerships withmore than two dozen PV companies, and in which thecompanies have shouldered 50% of the R&D costs.

These partnerships have improved manufacturing tech-nology by improving equipment, reducing the numberof steps in a process, automating assembly processes,reducing breakage and waste, and increasing through-put — the rate at which PV materials and devices arepassed through themanufacturing process.

The R&D partnershipshave strengthened theperformance and relia-bility of products byincreasing the conversion efficiencies of cells andmodules, increasing module lifetime with bettermounting techniques and encapsulants, and byimplementing internationally recognized qualityassurance procedures.

Since 1992, this R&D has helped drop modulemanufacturing costs for industry partners bymore than 30%. It has helped increase produc-tion capacity by more than five fold. And we antic-ipate that this type of progress will continue, so thatby 2004 we expect to see manufacturing capacitygrow another seven fold and module manufacturingcosts drop another 50%.

All of this has resulted in a win-win situation, with thepublic and industry recovering their investments,through cumulative decreased product costs for theconsumer and through increased profit (decreased loss)for the manufacturer. By 2004, industry will have recov-

ered 15 times its initial investment, and the publicwill have benefited by a factor of23. This trend will enhance theopportunity for investment ingreater production capacity forU.S. PV manufacturers.

The investment opportunities willbe further enhanced with ongo-ing manufacturing R&D partner-ships, which are continuing toimprove module manufacturingprocesses as well as investigatingconcepts such as:

• AC modules for easy plug-in resi-dential use (PV modules normally

produce DC electricity)

• Less expensive, easy-to-install residentialsystems that integrate the modules with stor-

age and inverter capabilities

• In-situ diagnostics and intelligent processing inte-grated directly into manufacturing lines.

The Program and industrywork together to move tech-

nology from the laboratoryto manufacturing, and to

increase the reliability andperformance of modules.

14

Under an R&D partnership with the Program, Energy ConversionDevices improved its high-quality production yields of a-Si cells. In thislong, 600-meter run, greater than 98% of the cells met specifications.

Other R&D issues in manufacturing include concernsabout materials utilization in thin films. For example, inmanufacturing a-Si modules, more than 90% of thegermanium (to alter the band gap of a-Si) is wastedduring deposition. Increasing the utilization rate to25% or higher would result in significant savings.

Also, the primarymethod for depositing

commercial a-Si — glow discharge —has a deposition rate of 1 to 3 Å/sec. Increasing

this rate to 10 to 100 Å/sec would also drop costsappreciably. A possible candidate for this would be avariation on the hot-wire deposition developed byNREL researchers.

Component reliability. All PV systems use compo-nents — batteries, control systems, inverters, etc. — toconvert, deliver, and store electricity generated bymodules. These components represent about half thecost of a system, but are responsible for the greatmajority of repair problems. Notorious among theseare inverters, whose failure in the field represents theprimary cause of system problems.

Recognizing this, Sandia is launching an initiative todesign and build an “inverter for the 21st century;” onethat would cost 25 cents per watt and have failure ratesless than 1%. To do so will take advances in circuit inte-gration, packaging, custom magnetics, and manufactur-ing. And it will take cooperation with industry, whichwill specify and design the inverter. Sandia will workhand-in-hand with industry and testing labs to evaluatethe inverter. Similarly, Sandia will evaluate the smallerinverters being designed and built by industry underother cooperative R&D projects with the Program.

Module Performance and Reliability

Companies bring their modules and systems to NRELand Sandia for testing and analysis, to improve systemreliability. By “reliable,” we mean that a system bothshould last long (up to 30 years, the long-term goal)

and generate 80% as much electricity toward the endof its lifetime as it did at the beginning. To this end,the Program investigates and improves reliability ofsystems using a five-prong approach:

Module testing. By subjecting modules to a vari-ety of outdoor conditions and acceleratedstress tests (under which modules arecycled through extreme condi-tions), researchers measuremodule performanceand identify failuremechanisms. Failuremechanisms and degra-dation rates from thesetests are correlated withlong-term field tests, andused to validate computermodels for predicting servicelifetime. Manufacturers use thesetests to re-engineer modules to cir-cumvent failures.

Accelerated testing of encapsulation materials.Browning, chemical decomposition (which affectsoptical, electrical, and mechanical properties of amodule), and delamination can limit module lifetimeand electricity production. Accelerated testing pro-motes a better understanding of the mechanisms ofaging and decomposition. This, in turn, leads to bet-ter module production techniques and better encap-sulation materials.

Solar radiometric measurements. Measuring thesolar radiation and its spectral content, with an accuracytraceable to national and international standards, pro-vides a base against which to measure and comparemodule and system performance. Also, knowing thespectral content of solar irradiance (i.e., the energyand intensity incident at particular solar wavelengths)enables us to understand degradation mechanisms,especially with respect to the ultraviolet portion oflight, which can be highly damaging to some materials.

Module and array performance. How do commer-cial modules perform over the long haul under fieldconditions? Answering this question helps correlate long-term performance with failure mechanisms identifiedunder accelerated stress testing. This helps manufacturersto design systems to overcome the failures and boostperformance. Efforts include developing outdoor moduleand array test procedures; characterizing electrical, ther-mal, and optical attributes of commercial modules; anddeveloping numerical tools that accurately model thepower and annual energy production from PV systems.

Module field durability research. Thoroughly ana-lyzing the degradation mechanisms of modules underlong-term exposure helps manufacturers developimproved processes to mitigate problems. This under-standing also lends to the Program's development ofmodule qualification testing, which can help manufac-turers produce long-term, high-performance modules.

Part of anautomated systemdeveloped bySpire under cooperative R&Dwith the Program,this assemblersolders solar cellstogether withinterconnecting

ribbon to formcell strings.

Aninfrared

technique developed bySandia for long-term testing ofmodules indicates“hot spots” and“cold spots” tolocate short-circuited cells.

15

Systems Engineering & ApplicationsMeeting the long-term goals of the PV Program andPV industry requires nothing less than launching theindustry anew in the 21st century, with systems andinnovative products that can accelerate expansion intowhole new markets.

This obliges the PV industry to make systems that meetthe performance, maintenance, and lifetime demandsof the user; that meet mechanical, electrical, andsafety codes and standards; and that may be easilyintegrated into a myriad of applications. And it obligesthe Program and industry to adequately informbuilders, developers, utilities, industry, and the publicabout PV systems, their capabilities, and applications.

Systems Engineering In the final analysis, it is performance, reliability, andlifetime of systems that are important to customers.

Consequently, the Program and industry areworking together to test how well systems per-form under real conditions for long periods oftime. These data will be entered into databasesand will be used to define standards by whichfield performance may be measured.

Similar testing is taking place to determine thereliability of systems in the field — how longthey last, how well they perform during theirlifetime, and how much maintenance they need.These data will be used to establish require-ments for a reliable 30-year system lifetime.

To boost the confidence that new systems willperform reliably for 30 years, the Program isdevising qualification protocols — establishingaccelerated test procedures whereby systems aresubjected to cycles of extreme temperature,humidity, mechanical, and electrical conditions todetermine how long they can be expected to lastand how well they can be expected to perform.For systems that pass these protocols, customerswill be assured of their quality and reliability.

Grid-tied systems should also meet connectionstandards (e.g., producing a high-quality AC sig-nal, and being able to automatically detach fromthe grid in case of emergency). To be sure theydo, the NCPV is working with utilities, the ElectricPower Research Institute, the Gas ResearchInstitute, and others to devise standards for grid-tied PV systems. This will help PV be ready tomeet the needs of the utility market.

PV Buildings Integration

The more than 100 millionresidences andcommercialbuildings inthe UnitedStates con-sume two-thirds of thenation’s electricity. Thisneed not be so. By incorpo-rating PV systems, buildings couldproduce electricity — for lights, coolingloads, fans, and more.

The concept of integrating PV into buildings has beenevolving for some time. In the 1970s, remote buildingsbegan using PV modules to supply small amounts ofelectricity. In the 1980s, residences and commercialbuildings started mounting PV arrays on their roofsand connecting them to the grid. In the 1990s, theProgram brought together PV manufacturers withmanufacturers of building products to develop PVsystems for integration directly into the building enve-lope — to be used in awnings, windows, spandrels,skylights, roofing shingles, and other structures.

Today, the idea is spreading, with architects, engi-neers, and builders incorporating PV into their build-ing designs. But more must be done for this conceptto become widespread. First, costs must drop. Due tocustomized designs, integrated PV systems can beexpensive. This may be mitigated by product standardi-zation, which would allow PV systems to be bought“off the shelf” and integrated into buildings.

Second, the PV industry must pay close attention to theneeds of the buildings industry, by making sure theirproducts meet codes, standards, and insurance require-ments, and that they design new products that meetreal building needs. Toward this end, the Program, thePV industry, and the buildings industry are cooperatingto develop cost-effective systems that blend well withbuilding materials and components. These include:

• PV-powered electrochromic windows (to shadesunlight and offset heating loads)

• Transparent thin-film products

• Alternating current PV modules

• Hybrid PV products that can offset both electricand heating loads

• New inverters that can be used with a string ofPV modules

• New roofing products.

Technology IntroductionIn June of 1997, President Clinton announced anambitious plan — the Million Solar Roofs Initiative — toput a million solar systems on American roofs by 2010.

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The 4 Times Square Building in New YorkCity integrates thin-film PV panels intothe mirror glass spandrels from the 35thto 48th floor. The panels produce 1.5%of the building‘s electrical needs.

This is a plan in which Americans — communities,organizations, state and federal agencies, businesses,institutes, and private citizens — cooperate to put PVto work for clean energy.

The role of the Program and the NCPV is to act as afocal point for technical information and education onPV, provide technical services, and provide a forumthrough which various organizations coordinate theiractivities. This is a paradigm of cooperation, in which alittle investment and much initiative may have impor-tant consequences.

The Million Solar Roofs Initiative is representative of thepartnerships that the NCPV forms to provide technicalinformation and services to help organizations imple-ment the technology. The NCPV also works with:

• Insurance companies and the Federal EnergyManagement Agency — who want to know howPV can power communication, light, and heat tomitigate the burden incurred by natural disasters

• Federal agencies such as the U.S. Forest Serviceand the National Park Service — who are interestedin using PV for remote power and communications

• Utilities and regulatory agencies — who want toknow how to use PV for on- and off-grid applica-tions, and who are concerned about PV perfor-mance and interconnection issues

• Farmers and ranchers — who could use stand-alone PV for electric fences and for pumpingwater for cattle or irrigation.

For the international market, PV is becoming a power ofchoice for applications ranging from water pumping,communications, and lighting, to village power.This is a fast-growing market, and the competitionis fierce to bring PV to more than 2 billion peoplein developing countries who are without electricity.

To help the U.S. industry make inroads and to helpcountries establish a PV infrastructure, the NCPV per-forms several functions, including:

• Facilitation — by working with U.S. industry, gov-ernment agencies, financial institutions, technicaland research organizations, and nongovernmentorganizations, to clear barriers to PV installations

• Education/testing — by working with indigenousgroups and national institutes to provide educationand training, perform testing, and devise testingprotocols

• Standardization — bycooperating withnational and interna-tional organizations todevelop PV perfor-mance, measurement,and interconnectionstandards

• Evaluation — by per-forming studies toassess the social, eco-nomic, environmental,and technologicalimpacts of PV

• Demonstration — by demonstrating new tech-nologies to ascertain their technical feasibility fornew or remote applications.

To date, the Program has helped introduce PV toBrazil, China, Ghana, India, Indonesia, Kenya, Mexico,Morocco, Pakistan, the Philippines, Russia, SouthAfrica, and Venezuela. In the next five years, theProgram will continue to extend and deepen this list.

As this list is extended, and as domestic and interna-tional markets expand throughout the next century,we will witness the unfolding of PV’s promise tobring clean, low-cost, high-tech energy to peopleand industry in allcorners of theglobe.

17

The Program — withindustry, governments,national and internationalorganizations — improvesperformance and reliabilityof systems and introducestechnology to domesticand foreign markets.

In a cooperative effort between DOE and India, 300 homes in West Bengal installed stand-alone PV systems to provide electricity for lights. This “seed” project stimulated the installation of 2000 more systems.

This 15-kW system uses innovativemodules developed in a cooperativeprogram with industry to supply ACelectricity for the Pentagon inArlington, Virginia.

Thin Films

High-Performance and Concentrator Research

Crystalline Silicon

Measurements andCharacterization

Basic andUniversity Research

ManufacturingResearch and Development

Module Performance and Reliability

SystemsEngineering and Reliability

Partnerships forTechnology Introduction

Program Integrationand Industry

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P hotovoltaics is an investment in America’sfuture. As we expand the boundaries ofenergy, PV serves America and improves

the quality of life on Earth. Our exploration iscovering new frontiers in:

• Science — where we investigate con-densed matter physics, quantum physics,photochemistry, photosynthesis, and bio-logical systems to push the limits ofknowledge on the interaction of lightwith matter . . . and where we synthesizenew materials and create new devicestructures to convert light to electricity.

• Technology — where we develop mod-ules and systems and engineer new tech-nologies to enhance manufacturingcapabilities . . . and where we are introduc-ing new thin-film and high-efficiencymaterials and devices that will continue torevolutionize the industry and drop thecost of electricity.

• Applications — where PV systems todayare being used in space, for communica-tions, on houses, and in remote places,expanding to every corner of the globe. . . and where tomorrow’s systems will beused in ever larger, more energy-signifi-cant applications as new materials anddevices emerge into the marketplace.

The promise of photovoltaics, however, goesbeyond energy. In synergy with other advanc-ing technologies — biology, solid-state andother materials, medicine, telecommunications,superconductivity, and renewable energy —PV will greatly influence our lives. It will helpbolster our economy and will spur us to rede-fine how we work and how we communicate.

The year 2000 is more than the start of a newmillennium. It is the start of a new energy era,in which PV will touch the lives of billions ofpeople on our planet.

18

Serving America

Support the successful transition of CIS tomulti-megawatt production

Demonstrate a monolithic, series-connected,multijunction polycrystalline thin-film device

Assess processes for solar-grade Si feedstockproduction

Refine and transfer manufacturing-friendlyelectro-optical-based diagnostic to PV industry

Assess results of EERE/Office of Science collaborations

Determine need for additional manufacturingR&D and identify areas of maximum impact, if appropriate

Document performance of commercial modules,based on energy production

Assess Million Solar Roofs Initiative, documentingnumber of residential and commercial systemsinstalled

Assess environment, safety, and health issuesassociated with multi-hundred-megawattmanufacturing and deployment of PV

• Technically assess thin-film system performance

• Demonstrate technology for remote dispatchof PV inverters

Demonstrate 10%-efficient commercial CdTemodule

Demonstrate achievement of voltage addition in4-junction device

Demonstrate 19%-efficient Si solar cell using allhigh-throughput processes

Complete capability to evaluate multiple-junctionconcentrator cells and modules to 1000X with±3% uncertainty

Identify promising PV options for future R&D

• Implement new partnerships to address processescapable of $1/watt direct module manufacturingcosts with gigawatt production capacity

• Demonstrate soft-switching inverters with 97%efficiency and < 1% failures

Validate accelerated test methods that reproducefailures/degradation observed in the field

• Validate 25-year lifetime for PV systems

• Develop PV system qualification test

Support insurance industry in adopting apremium benefit for owners of PV-poweredbuildings

Examine PV Program contributions to meeting 20-Year Industry Roadmap

Five-Year PV Program Technical Areas and Milestones

Assess progress and structure of Thin FilmPartnership and begin recompetition process

Initiate projects targeting a doubling of PVperformance from 1999 commercial levels

Assess viability of back-contact Si solar cells

Initiate R&D on process diagnostics andintegration

Expand fundamental R&D for conventional andnonconventional PV technologies

Identify and focus on new projects on intelligentprocessing, in-situ diagnostics, and related areasto meet industry needs

• Establish qualified databases to assess operationand maintenance and lifetime for grid-tied andstand-alone systems

• Facilitate development of PV interconnectionstandard (IEEE 929)

Assess impact of PV in developing countries anddocument performance from past projectinitiatives

Industry publishes PV 20-Year Roadmap

• Demonstrate stable 13%-efficient a-Si cell

• Demonstrate 20% polycrystalline thin-film cell

Assess technical issues for high-concentrationsystems

Demonstrate potentially low-cost, high-quality,thin-layer crystalline Si growth on a foreignsubstrate

Develop and implement an electro-optical-baseddiagnostic compatible with manufacturingenvironments

Assess viability of dye-sensitized solar cell

Evaluate balance-of-systems componentprogress and future needs

Publish comparison of module energy-ratingmethods

• Obtain national accreditation and certificationprogram for installation and acceptance ofPV systems

• Complete development of test procedure todetermine performance of stand-alone systems

NCPV to assess contributions of TechnologyExperience to Accelerate Markets in UtilityPhotovoltaics (TEAM-UP) to U.S. utilityPV program

Start construction of NCPV Science andTechnology Facility

• Demonstrate 17%-efficient CdTe cell

• Support the successful transition of CdTe to multi-megawatt production

Demonstrate feasibility of a 3-junction device for38%-efficient solar cell under concentration

Demonstrate 18%-efficient, large-area multi-crystalline-Si solar cells using commerciallycompatible processes

Initiate next in series of international cell andmodule performance intercomparisons

Assess contributions of Historically Black Collegesand Universities projects

Achieve module manufacturing processes capable of $2/watt direct module manufacturingcosts with 250-megawatt production capacity

Document failure/degradation mechanisms ofthin-film and crystalline modules

• Establish requirements for 25-year systems

• Facilitate and lead IEEE development ofinterconnection standard for distributedgeneration

Increase adoption of PV backup power suppliesby federal and state disaster relief organizations

Issue revised DOE PV Program Five-Year Plan

• Help develop and publish a qualificationstandard for concentrator modules (Institute ofElectrical and Electronic Engineers [IEEE] 1513)

• Update performance indicators of 30-yearmodule lifetime

2000 2001 2002 2003 2004

T his Photovoltaic Program Five-Year Planis being published today, January 1,2000. It is the first day of a new century

that will eventually be powered by renewableenergy technologies like photovoltaics (PV).

In the PV community, there is a sense of excite-ment and challenge — the same feeling mem-bers of the Apollo program must have felt atthe start of the moon race. In 1999, we cele-brated the 30th anniversary of Apollo 11'ssuccessful mission. A little more than a yearago, the Mars Sojourner Rover, entirely poweredby PV, completed its mission. The challenge weface in this century is to enable PV to go as faras any other energy technology here on Earthby making the scientific and technologicaladvances that will put PV on every rooftop andin every corner of the globe. Like the spaceprogram, a balanced, aggressive PV researchand development program has the potential toopen a new frontier here on Earth.

When John F. Kennedy challenged the nationto put a man on the moon within a decade,the scientists who would lead the effort hadlittle more than a mission from their Presidentto guide them. But that was enough toinspire them to the hard work and dedicationit took to create a plan, a program, and finally,the technology that would open a new fron-tier in space. Our mission is alsobold and inspiring —to offer the

world a cost-effective, reliable technologythat turns sunlight into energy with no pollu-tion, wherever it is needed.

Apollo’s scientists, engineers, and astronautspursued their mission with perseverance, inge-nuity, and scientific curiosity and in the processchanged the way we view our planet and ourfuture. They were the first to capture the view,featured on the cover of this five-year plan, ofthe Earth as a lone planet surrounded by thevastness of space. For many, it signified the lim-its of the Earth and our resources, and theoverriding need to protect our environment.For others, the fact that science and technologyhad allowed people to leave Earth and lookback on our planet from the moon signified theability of science and technology to overcomeall limitations. The entrepreneurs, scientists, andengineers that make up the PV communityrepresent the best of both views — a beliefthat science and technology, guided by pur-pose and vision, can overcome all limitationsand tap new energy resources that also protectour global environment.

The PV industry has created a new technologyroadmap to chart industry’s course. This five-year plan provides a strategy for research and

Taking Steps Toward a New Energy Front

Taking Steps Towarda New Energy Frontier . . . . . . .2

Photovoltaics — Energy for the New Millennium . . . . . . . . .4

• The Promise of Photovoltaics• A National Endeavor

• Guiding the Effort

The Research Program —Delivering the Promise . . . . . .10

• Research and Development• Technology Development

• Systems Engineering & Applications

2

Industry Roadmap 2000–2020

T he U.S. photovoltaic industry has long been theworld’s leader in research, technology, manufactur-ing, and markets. During the last several years, how-

ever, other nations have recognized the importance of thistechnology and have accelerated their own strategic incen-tives toward securing dominant global positions.

To meet growing market demand, confront increasingforeign competition, and retain and build its leadershipposition, U.S. PV companies have devised a unified indus-try roadmap with a vision, and with long-term (throughthe year 2020) strategies and goals.

The Vision

. . . to provide the electrical/energy consumer competitiveand environmentally friendly energy products and servicesfrom a thriving United States-based solar-electric powerindustry.

The Strategies

• Maintain the U.S. industry’s worldwide technologicalleadership.

• Achieve economic competitiveness with conventionaltechnologies.

• Maintain a sustained market and PV productiongrowth.

• Make the PV industry profitable and attractive toinvestors.

The Goals

• Maintain a 25% annual production growth rate.

• During 2020, ship approximately 7 peak gigawatts(GWp) of PV for installation worldwide, 3.2 GWp ofwhich will be used in domestic installations.

• Drop costs to the end user (including costs for opera-tion and maintenance) to $3.00 per watt AC by 2010and to approximately $1.50 per watt AC by 2020.

The roadmap serves as a guide for the industry and thePV community. Its success depends on the direction,resources, best scientific and technological approaches,use of the best and most advanced technologies, andcontinued efforts of the “best and brightest” amongindustry, federal laboratory, and university partners.

Printed with renewable-source ink on paper containing at least50% wastepaper, including 20% postconsumer waste

Credits

Pages 2-3 Sandia NationalLaboratories/PIX04923 • p.4 Warren Gretz,NREL/PIX07158 • p.5 Richard Peterson/PIX01443 •p.6 Jim Yost Photography/PIX01816 • p.7 Siemens SolarIndustries/PIX06142 • p.8 U.S. Department of Energy/PIX04125 • p.9 Idaho Power Company/PIX01585 • p.10Jim Yost Photography/PIX01436 • p.11 Jim Yost Photography/PIX01462 • p.12 Jim Yost Photography/PIX07103 • p.13Bhushan Sopori, NREL/PIX03521 • p.15 Spire Corporation/PIX07526 • p.15 Sandia National Laboratories/PIX08309 •p.16 Kiss + Cathcart Architects/PIX06456 • p.17 John Thornton,NREL/PIX06249 • p.17 Harin Ullal, NREL/PIX04579.

Special thanks to Gary Cook, Ray David, Don Gwinner, andAlfred Hicks at the National Renewable Energy Laboratory forwriting, design, layout, and editing. Robert McConnell andJack Stone served as technical advisors.

For More InformationU.S. Department of EnergyJames E. Rannels, Director

Office of Solar Energy Technologies

1000 Independence Ave., SWWashington, DC 20585(202) 586-1720

U.S. Department of EnergyRichard King, Team Leader

Photovoltaics Program1000 Independence Ave., SWWashington, DC 20585(202) 586-1693

National Renewable Energy Laboratory

Lawrence Kazmerski, DirectorNational Center for Photovoltaics

1617 Cole BoulevardGolden, CO 80401-3393(303) 384-6600

National Renewable Energy Laboratory

Thomas SurekTechnology ManagerPhotovoltaics Program

1617 Cole BoulevardGolden, CO 80401-3393(303) 384-6471

Sandia National LaboratoriesChris Cameron, Manager

Photovoltaics ProgramP.O. Box 5800Albuquerque, NM 87185-5800(505) 844-3154

http://www.eren.doe.gov/pv

Produced for the U.S. Department of Energy1000 Independence Avenue, SWWashington, DC 20585

by the National Renewable Energy Laboratory1617 Cole Boulevard • Golden, Colorado, 80401-3393 • (303) 275-3000

NREL is a national laboratory of the U.S. Department of Energyoperated by Midwest Research Institute • Battelle • BechtelContract No. DE-AC36-99GO10337DOE/GO-10099-940January 2000