ILGAR technology. VIII. Sulfidic buffer layers for Cu(InGa)(S,Se) 2 solar cells prepared by ion layer gas reaction (ILGAR)

The ion layer gas reaction (ILGAR) is a novel deposition technique for chalcogenide compounds. This sequential and cyclic method, which involves a solid-gas reaction, is used to deposit sulfidic buffer layers on Cu(InGa)(S,Se)₂ (CIGSSe) absorbers. Chemical pretreatments of the absorber in several metal salt baths are investigated, which improve the device performance of the solar cell significantly. In the case of a Zn-bath a temperature above 100°C forces the modification of the absorber surface resulting in a drastic increase of the open circuit voltage with increasing bath temperature. As a first result the combination of Cd-pretreatment and ILGAR-CdS buffer in a solar cell (0.5 cm²) yields an efficiency of 14.2 % (total area) comparable with the quality of the corresponding standard device (CBD-CdS buffer, η=14.1%); the Cd-free combination of Zn-pretreatment and ILGAR-ZnS buffer also results in a device with an efficiency of 14.2 % (total area)