Interface formation between polycrystalline Cu(In,Ga)Se/sub 2/ and II-VI-compounds

The interface between Cu(In,Ga)Se/sub 2/ (absorber) and CdS (buffer) is crucial for the performance of CIGS thin film solar cells. We have performed systematic studies of interface formation between Cu(In,Ga)Se/sub 2/ and II-Vl semiconductors CdX and ZnX (X= S, Se, Te) using in-situ photoelectron spectroscopy. Clean Cu(In,Ga)Se/sub 2/ surfaces with Cu deficient surface composition were prepared by heating-off of Se layers, which were deposited onto the absorber layers in the deposition chamber directly after absorber deposition. Interfaces with II-VI compounds were prepared by stepwise evaporation. The determined band alignments are compared to theoretical calculations.