It was recalled that Cd-free Cu(In,Ga)(S,Se)2-based thin film solar cells with a nominal In2S3 buffer layer deposited by the spray ion layer gas reaction technique resulted in photovoltaic performances comparable to that of CdS buffered references. It had been previously argued that diffusion processes across the In2S3/ Cu(In,Ga)(S,Se)2 interface played a significant role in device quality. Investigating the interface formation by using X-ray photo-electron spectroscopy, it was possible to confirm a strong interfacial diffusion involving Cu and Na from the Cu(In,Ga)(S,Se)2.

Deposition of In2S3 on Cu(In,Ga)(S,Se)2 Thin Film Solar Cell Absorbers by Spray Ion Layer Gas Reaction - Evidence of Strong Interfacial Diffusion. M.Bär, N.Allsop, I.Lauermann, C.H.Fischer: Applied Physics Letters, 2007, 90[13], 132118