Microstructural characterisation of CuInS2 polycrystalline films sulfurised by rapid thermal processing

CuInS2 layers for solar cells have been sequentially prepared by a rapid th ermal process using sulfurisation in molecular S. Samples taken from the pr ocess at different sulfurisation times have been analysed by Raman scatteri ng, AES and TEM in combination with EDX in order to investigate the sulfuri sation process. After deposition of the Cu and In precursors, a bilayer str ucture is formed: Cu at the lower part and a Cu-In alloy at the upper. The results indicated that the sulfurisation starts at the surface by directly converting the Cu-In alloy into CuInS2. During further processing, the sulf urisation continues at the already formed CuInS2-(Cu-In) alloy and CuS is f ormed at the surface of the sample. After only 120 s of processing, complet e sulfurisation is achieved, leading to a bilayer structure CuS/CuInS2. The electrical performance of solar cells made from the absorber layers show n o diode behaviour as long as binary Cu-ln phases are present acid, for the latter sample, a record 11.4% efficiency has been achieved. (C) 2001 Elsevi er Science B.V. All rights reserved.