We review published literature from 1975 to the present for accelerated stress testing of flat-plate terrestrial photovoltaic (PV) modules. An important facet of this subject is the standard module test sequences that have been adopted by national and international standards organizations, especially those of the International Electrotechnical Commission (IEC). The intent and history of these qualification tests, provided in this review, shows that standard module qualification test results cannot be used to obtain or infer a product lifetime. Closely related subjects also discussed include: other limitations of qualification testing, definitions of module lifetime, module product certification, and accelerated life testing. Copyright © 2008 John Wiley & Sons, Ltd.

http://tu-freiberg.de/sites/default/files/media/institut-fuer-angewandte-physik-7681/scripts/osterwald2008.pdf

History of accelerated and qualification testing of terrestrial photovoltaic modules: A literature review

Solar technologies are projected to increase tremendously over the next 10 years. Glasses are playing an important role as transparent materials of photovoltaic (PV) cells and concentrating solar power (CSP) systems. Glasses are materials of short energy payback time and environmental compatibility suitable for sustainable energy concepts. The paper reviews recent solar applications. Surface structuring and coating of glasses are shown to improve energy efficiency for solar conversion systems substantially. Encapsulated glass-to-glass PV modules and solar photocatalytic glass surfaces are identified as elements of a green architecture combining renewable power generating and destruction of air pollutants of urban environments. Emerging solar technologies for power generation, including transparent PV modules, solar chimney and thermoelectric systems may become significant areas of future solar glass applications.

Glasses for solar energy conversion systems

Cadmium telluride (CdTe) with a room-temperature bandgap energy of 1.45 eV has been shown to be the most promising low-cost, thin-film photovoltaic material for terrestrial applications. Significant progress has been made during the past several years, and thin-film CdTe solar cells of > 1 cm2 area with conversion efficiencies higher than 12% have been prepared by several techniques. Thin-film CdTe photovoltaic modules with 10% efficiency have also been produced. They are of the heterojuntion configuration using a transparent conducting semiconductor (TCS) as the window and p-CdTe as the absorber. In this paper, the potential window materials for thin-film CdTe solar cells are discussed. Thus far, cadmium sulphide (CdS) with a bandgap energy of 2.42 eV at room temperature has been found to be best suited for efficient CdTe solar cells. the deposition techniques for p-CdTe films capable of producing efficient solar cells, including close-spaced sublimation (CSS), electrodeposition, screen printing and spraying, are briefly reviewed, and the characteristics of the resulting solar cells are discussed. It is concluded that the efficiency of thin-film CdTe solar cells can be increased to 18-19% in the near-term, leading to 15-16.5% efficient modules.

Recent progress in thin‐film cadmium telluride solar cells

Thin-film solar cells based on the chalcopyrite Cu(In,Ga)Se2 (CIGS) absorber material show high potential for further cost reduction in photovoltaics. Compared with polycrystalline silicon (p-Si) wafer technology, thin-film technology has inherent advantages due to lower energy and material consumption during production but has typically shown lower conversion efficiency. However, in the past two years, new scientific insights have enabled the processing of CIGS solar cells with efficiencies up to 21%, surpassing the p-Si wafer value of 20.4% efficiency for the first time. Now several research groups report record cell efficiency values above 20% using different deposition processes and buffer layers. The presence of potassium was observed in many CIGS devices over the years, but it is only very recently that differences with Na have started being taken into full consideration for device processing and that K was added intentionally to the absorber. In this study, previous reports showing the presence of potassium are reviewed and discussed in more detail. Furthermore, on a scale-up perspective, additional progress has also taken place with CIGS minimodules achieving efficiency up to almost 19% and where further increase can be expected in the near future with the improvements induced by the use of potassium. This shows that the CIGS technology is continuously progressing not only on scientific level but on technological level as well.

Cu(In,Ga)Se $_{\bf 2}$ Thin-Film Solar Cells and Modules—A Boost in Efficiency Due to Potassium

Surface passivation of polycrystalline, chalcogenide based photovoltaic cells

Two candidate polycrystalline thin film materials, CuInSe2, and CdTe, have emerged as potential leaders in the effort to develop low-cost photovoltaics. Until recently, most progress in these materials was on a laboratory scale. For instance, small CuInSe2 cells have reached 14.1% (ARCO Solar), Photon Energy and Ametek have achieved 12.3% and 11% efficiencies for CdTe. However, both technologies are now moving toward commercial products and are being developed for power modules. Issues relating to their scale-up to manufacturing are increasingly germane.

CuInSe2 and CdTe Scale-up for Manufacturing

Polycrystalline thin-film materials based on copper indium diselenide (CuInSe2, CIS) and cadmium telluride (CdTe) are promising thin-film solar cells for various power and specialty applications. Impressive results have been obtained in the past few years for both thin-film copper indium gallium diselenide (CIGS) solar cells and thin-film CdTe solar cells. NCPV/NREL scientists have achieved world-record, total-area efficiencies of 19.3% for a thin-film CIGS solar cell and 16.5% for thin-film CdTe solar cell. A number of technical R&D issues related to CIS and CdTe have been identified. Thin-film power module efficiencies up to 13.4% has been achieved thus far. Tremendous progress has been made in the technology development for module fabrication, and multi-megawatt manufacturing facilities are coming on line with expansion plans in the next few years. Several 40-480 kW polycrystalline thin-film, grid-connected PV arrays have been deployed worldwide. Hot and humid testing is also under way to validate the long-term reliability of these emerging thin-film power products. The U.S. thin-film production (amorphous silicon[a-Si], CIS, CdTe) is expected to exceed 50 MW by the end of 2005.

/pdf/polycrystalline-thin-film-photovoltaic-technology-4v3yrpm1wi.pdf

Polycrystalline thin film photovoltaic technology

Cells and Modules

We have attempted to select and examine the key processes for making CuInSe 2 and CdTe as well as for fabricating window materials and oxide and metal contacts. For example, we have sections on selenization of Cu and In to make CuInSe 2 and on electrodeposition and spraying to fabricate CdTe (among others). We also have sections on depositing Mo contacts and fabricating ZnO and SnO 2 . We have attempted to survey the entire process spectrum from substrate to finished cells. We have also touched upon materials issues such as availability and toxicity. We have summarized the status and issues of the various approaches as well as given a set of conclusions concerning their advantages and disadvantages in relation to the alternatives

CuInSe2 and CdTe: scale-up for manufacturing

High-efficiency, low-cost thin film solar cells are an exciting photovoltaic technology option for generating cost-effective electricity in 1995 and beyond This paper reviews the substantial advances made by several thin film solar cell technologies, namely, amorphous silicon, copper indium diselenide, cadmium telluride, and polycrystalline silicon Recent examples of utility demonstration projects of these emerging materials are also discussed 8 refs, 4 figs

/pdf/recent-technological-advances-in-thin-film-solar-cells-55oxbruct0.pdf

Kenneth Zweibel

Papers

CuInSe2 and CdTe Scale-up for Manufacturing

Polycrystalline thin film photovoltaic technology

Cells and Modules

CuInSe2 and CdTe: scale-up for manufacturing

Recent technological advances in thin film solar cells