Fabrication of selenization-free superstrate-type CuInS2 solar cells based on all-spin-coated layers

Today manufacturing of high efficiency chalcogenide thin film solar cells is based on high cost vacuum-based deposition processes at high temperature (>500 °C) and in chalcogen -containing atmosphere. In this paper, we introduce a simple vacuum-free and selenization-free, solution processing for fabricating a superstrate-type CuInS2 (CIS) solar cell. The absorber, buffer and blocking layers were all deposited by spin coating of molecular precursor inks. We demonstrate the deposition of In2S3 buffer layer by sol-gel spin casting for the first time. The rapid sintering process of CIS layer was carried out at 250 °C that is considered a very low temperature in CIGS thin-film technologies. A novel molecular-ink route to deposit In2S3 type buffer layer is presented. For the back contact we employed carbon, deposited by simple knife coating method. Different parameters including type of buffer, thickness of absorber layer, CIS and In2S3 annealing temperature and morphology were optimized. Our air stable simple device structure consisting of  showed promising power conversion efficiency (PCE) of 2.67%.