Mechanism analysis of CuInS₂ and Cu(In,Ga)S₂ growth via KCN- and H₂S-free process and solar-cell application

Abstract

In this article, CuInS2 (CIS) and Cu(In,Ga)S2 (CIGS) absorbers are prepared via sulfurization by a sulfur powder source for co-evaporated Cu–In(–Ga) metal precursors without toxic KCN and H2S. The CIS and CIGS growth mechanism during sulfurization and its application to solar cells are discussed. X-ray diffraction (XRD) and Raman spectroscopy analyses, indicate that CuS and (In,Ga)2S3 exists at the frontside and the backside, respectively, in the CIGS films at the temperature between 250–350 °C. Then, these intermediate phases react at 400 °C or higher forming CIGS. Finally, CIS and CIGS solar cells with the efficiencies of 3.7% and 7.2% are achieved, utilizing optimum temperature of 600 °C.