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

Rapid thermal processing (RTP) provides a way to rapidly heat substrates to an elevated temperature to perform relatively short duration processes, typically less than 2–3 minutes long. RTP can be utilized to minimize the process cycle time without compromising process uniformity, thus eliminating a bottleneck in CuIn_1-xGa_xSe_2-yS_y (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. Florida Solar Energy Center (FSEC) PV Materials Lab has developed excellent facilities for the preparation of CIGSS thin-film solar cells. A RTP reactor for preparation of CIGSS thin films on 10 cm × 10 cm substrates has been designed, assembled and tested at the FSEC PV Materials Lab. This paper describes the synthesis and characterization of CIGSS thin-film solar cells by RTP technique. Materials characterization of these films was done by SEM, XEDS, XRD, AES, EPMA and electrical characterization was done by current-voltage measurements on soda lime glass substrates by 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.