Preparation of CIGSS Thin-Film Solar Cells by Rapid Thermal Processing

Abstract

Rapid thermal processing (RTP) provides a way to rapidly heat substrates to an elevated temperature to perform relatively short duration processes, typically less than 2–3min long. RTP can be utilized to minimize the process cycle time without compromising process uniformity, thus eliminating a bottleneck in CuIn1−xGaxSe2−ySy (CIGSS) module fabrication. Some approaches have been able to realize solar cells with conversion efficiencies close or equal to those for conventionally processed solar cells with similar device structures. A RTP reactor for preparation of CIGSS thin films on 10cm×10cm substrates has been designed, assembled, and tested at the Florida Solar Energy Center’s PV Materials Lab. This paper describes the synthesis and characterization of CIGSS thin-film solar cells by the RTP technique. Materials characterization of these films was done by scanning electron microscopy, x-ray energy dispersive spectroscopy, x-ray diffraction, Auger electron spectroscopy, electron probe microanalysis, and electrical characterization was done by current–voltage measurements on soda lime glass substrates by the RTP technique. Encouraging results were obtained during the first few experimental sets, demonstrating that reasonable solar cell efficiencies (up to 9%) can be achieved with relatively shorter cycle times, lower thermal budgets, and without using toxic gases.