Cadmium-free buffer layers deposited by atomic later epitaxy for copper indium diselenide solar cells

As a soft and highly controllable deposition technique, atomic layer epitaxy (ALE) is well suited to deposit buffer and window layers on CIS thin solar films with high interface quality. In this work we have investigated ALE buffer layers of zinc oxysulfide, indium sulfide and aluminum oxide deposited at low temperature (160°C). The most promising results have been obtained with using indium sulfide buffer layers, with a record efficiency of 13.5% (30.6 mA /cm2, 604 mV, FF=0.73 under 100 mW /cm2, without AR coating) achieved on a standard CIGS absorber. This opens a route for a dry cadmium-free buffer process fully compatible with the other vacuum deposition techniques (coevaporation, sputtering).