Toward High Performance Epitaxial and Low-temperature Cu ( In , Ga ) Se 2 Solar Cells
The CIGS research effort at the University of Illinois represents a three-pronged approach to understanding and solving some of the most critical issues in CIGS device. These three prongs are: (1) development of a basic understanding of the issues limiting performance in CIGS devices, (2) advancing the performance of the devices through single crystal epitaxial layers for integration into high-performance cells, and (3) developing novel growth processes that will allow lower deposition temperatures necessary to multijunction devices. This paper presents an approach for CIGS/GaAs and CIGS/Ge heterojunction solar cells for multijunction high-efficiency devices. In addition, application of ionized physical vapor deposition to lowtemperature deposition of CIGS is described. The two projects will be coupled and results from one used to enhance progress in the other as part of the Beyond the Horizon and High Performance PV programs now starting.
DOE/NREL fundamental and exploratory research into solar cells
The U.S. Department of Energy/National Renewable Energy Laboratory supports fundamental and exploratory research into solar cells. The purpose of the following set of research projects is twofold: (1) to provide fundamental experimental and theoretical foundations to existing photovoltaic (PV)/solar cell technologies, and (2) to explore whole new possibilities in PV/solar cell technologies, however revolutionary or nonconventional they might be. As surely as a number of revolutionary new solar cell technologies will most likely involve high-risk, long-term R&D to bring them to fruition, and may also well be needed as a complement to a future energy portfolio, so we also need timely results. As such, one of the primary driving motives for this effort is the possibility of developing one or more "leapfrog" technologies. These are technologies that have the distinct possibility of "leaping ahead" of existing technologies rather than taking the more characteristic development time of 10 to 20 years.
Reactive sputtered CuInSe2
Abstract The deposition of CuInSe 2 thin films by co-sputtering from copper and indium planar magnetron sputtering sources in a working gas of argon plus H 2 Se is being investigated. Near-stoichiometric coatings deposited onto glass and molybdenum-coated substrates have been found to have resistivities, Hall mobilities, absorption coefficients, band gaps, surface topographies, grain sizes and oxygen heat treatment behavior comparable with those of films produced by the more common three-source evaporation method. However, it has not been possible by reactive sputtering to deposit indium-rich films ([In]/[Cu] ≈ 1.5) of the type commonly used as a top layer in the preparation of two-layer device quality films by the evaporation method. Apparently an indium-rejection behavior, which occurs during the deposition process in H 2 Se reactive sputtering, makes it difficult to achieve indium compositions beyond the amount that can be incorporated into the CuInSe 2 chalcopyrite phase. Experiments are described which were conducted to examine the dependence of the indium-rejection behavior on the deposition conditions.