W. Luft

Second controlled light-soaking experiment for amorphous silicon modules

Dual-junction and triple-junction amorphous silicon modules from three manufacturers were subjected to light soaking at 1-sun intensity at 50/spl deg/C, loaded to the maximum power point, for 1000-2000 hours, with annealing to 70/spl deg/C in the dark after 1000 hours. Performance characterization was done periodically, both under a pulsed solar simulator and outdoors. Aperture-area efficiencies as high as 9.1% were obtained after 1000 hours of light-soaking. The power output after 1000 hours of light soaking and subsequent partial annealing ranged from 77% to 92% of the initial power output. The recovery in power due to annealing was 4%-6.5%. For a-Si/a-Si-type modules, stabilized performance was reached before 1000 hours. The validity of the results is discussed in detail.<<ETX>>

Prospects for amorphous silicon photovoltaics

Abstract Significant progress has been achieved in amorphous silicon photovoltaic technology since the first commercial square-foot-size modules were introduced in 1984. Over the years, quality control, materials, module size, and module packaging have improved, but the basic cell structure used in the modules has changed little. Based on the manufacturing experience since 1984 and prototype module research, larger and more advanced manufacturing plants have been designed, are under construction, or coming on line soon. The economics of large-scale photovoltaic systems may force reconsideration of amorphous silicon module design and construction, which, for the most part, has been directed toward small power systems. This paper summarizes progress that has been made since 1984, discusses expectations for photovoltaics in general, and presents the technological path amorphous silicon technology is pursuing to become competitive in the photovoltaics market.

Status of the DOE/SERI Amorphous Silicon Research Project: recent advances and future directions

Recent advances in material, cell, and module research in the US Department of Energy/Solar Energy Research Institute (DOE/SERI) Amorphous Silicon Research Project (ASRP) are reviewed. Advances in transparent conductive oxides, high-performance back reflectors, cell interconnection/patterning schemes, and encapsulants are surveyed. The program phase that began in 1990 has major research goals of reproducible, cost-effective multijunction modules (900 cm/sup 2/ area) with stabilized efficiencies of 10% for same-bandgap modules and 12% for different-bandgap modules. The issue of stability and reliability of amorphous silicon modules is reviewed. Multijunction cell/module structures have demonstrated improved stability in R&D cells and modules over single-junction structures.<<ETX>>

Considerations for light soaking of amorphous silicon photovoltaic modules

To estimate the stabilized performance a priori, laboratory tests under controlled, simulated 1-Sun, conditions have been performed on hydrogenated amorphous silicon (a-Si:H) multijunction solar cell modules by various organizations. Such tests generally use an arc light source and maintain the module temperature at some fixed value, e.g. 50/spl deg/C. Because the spectra of various light sources used for light soaking do not match that of the Sun and because the operating temperature for real systems is not constant and differs from the fixed temperature in laboratory tests, the validity of the laboratory light soaking tests has been questioned. The paper examines the most significant parameters in light-soaking tests to determine their effect and to indicate test strategies to minimize any errors caused by these parameters that may tend to invalidate the results. There is a significant difference (up to a factor of 3) in the relative (to AM 1.5) intensity to which various layers of solar cells are subjected depending on the light source spectra. The effect of temperature during light exposure on the stabilized performance varies between a-Si devices of different structures. The aim of this paper is to determine whether a specific standardized, continuous light-soaking test in principle can predict the stabilized performance that will be observed when modules with different a-Si:H-based layers are deployed outdoors.

Needs of the amorphous silicon program with respect to stabilized module performance

Abstract Amorphous silicon technology offers an avenue for low-cost thin film photovoltaic applications. The performance of amorphous silicon-based solar cells is limited by light-induced degradation. Inadequate description of the electronic phenomena in these materials and devices hampers resolution of this problem. We are posing questions which should stimulate researchers to develop better descriptions for device performance and better microscopic models for defect sites. The issue of Staebler-Wronski degradation should not be addressed separately from initial performance, but research should focus on material and device properties in the stabilized state. The main focus of a-Si:H research sponsored by the U.S. Department of Energy will be improvement of stabilized performance, which we anticipate to accomplish through focused development of optimized multijunction device structures, combined with an improved understanding of materials.

The US DOE/NREL amorphous silicon photovoltaics program

The recent advances of the US Department of Energy (DOE)/National Renewable Energy Laboratorys (NRELs) amorphous silicon photovoltaics program are reviewed. Research conducted at universities, industry, and government laboratories is addressing the critical technological issues of increasing photovoltaic module reliability and improving the stabilized performance. Multijunction device structures have demonstrated higher stabilized efficiencies than those of single-junction devices. In addition, novel deposition techniques and modifications to conventional deposition techniques have produced intrinsic amorphous films with improved stability that have not been fully realized in devices. Results are given for multijunction module performance after continuous 1000 h of illumination at one-sun intensity and 50 degrees C module temperature. These conditions are used as a predictor for stabilized performance.<<ETX>>

Advances in material/cell/submodule research in the DOE/SERI amorphous silicon research project

Advances in material, cell, and submodule research in the DOE/SERI Amorphous Silicon Research Project (ASRP) are reviewed. The program was initiated in 1987, directed toward achieving the following objectives in 1990: (i) efficiencies of 10% and 13% respectively, for amorphous silicon single-junction and multijunction submodules (1000 cm/sup 2/) and (ii) an efficiency of 18% for multijunction cells (1 cm/sup 2/), with associated stability criteria. Efficiency levels are currently at 9.4% and 11.1% for single-junction and multijunction submodules and at 13.14% for multijunction cells. A review is also given of major highlights in fundamental research activities.<<ETX>>

Stabilized module performance as a goal for the photovoltaic amorphous silicon program in the United States

Amorphous silicon technology offers an avenue for low‐coast, thin‐film photovoltaic applications. The performance of amorphous silicon‐based solar cells is limited by light‐induced degradation. The inadequate existing understanding of the electronic phenomena in amorphous silicon materials and devices hampers resolution of this problem. We are posing questions that should stimulate researchers to develop better descriptions for device performance and better microscopic models for defect sites. The issue of Staebler‐Wronski degradation should not be addressed separately from initial performance, but research should focus on material and device properties in the stabilized state. The main focus of the a‐Si:H research sponsored by the United States Department of Energy will be on improving the stabilized performance, which we anticipate to accomplish through focused development of optimized multijunction device structures combined with an improved understanding of materials.

THE UNITED STATES PHOTOVOLTAIC AMORPHOUS SILICON PROGRAM: STABILIZED MODULE PERFORMANCE

Amorphous silicon technology offers an avenue for low-cost, thin-film photovoltaic applications. The performance of amorphous silicon-based solar cells is limited by light-induced degradation. Inadequate description of the electronic phenomena in these materials and devices hampers resolution of this problem. We are posing questions that should stimulate researchers to develop better descriptions for device performance and better microscopic models for defect sites. The issue of Staebler-Wronski degradation should not be addressed separately from initial performance, but research should focus on material and device properties in the stabilized state. The main focus of a-Si:H research sponsored by the United States Department of Energy will be on improving the stabilized performance, which we anticipate to accomplish through focused development of optimized multijunction device structures combined with an improved understanding of materials.