• 
  Weinhardt, L.; Bär, M.; Pookpanratana, S.; Morkel, M.; Niesen, T.P.; Karg, F.; Ramanathan, K.; Contreras, M.A.; Noufi, R.; Umbach, E.; Heske C.: Sulfur gradient-driven Se diffusion at the CdS/CuIn(S,Se)₂ solar cell interface. Applied Physics Letters 96 (2010), p. 182102/1-3

10.1063/1.3425666

Abstract:
The diffusion behavior of Se at the CdS/Cu(In,Ga)(S,Se)2 thin film solar cell interface was investigated by x-ray photoelectron spectroscopy and x-ray excited Auger electron spectroscopy. Buffer/absorber structures with S/Se ratios between zero and three at the initial Cu(In,Ga)(S,Se)2 surface were analyzed. Samples from a high-efficiency laboratory process (NREL) as well as from an industrial large-area process (AVANCIS) were investigated. We find selenium diffusion into the CdS buffer layer, the magnitude of which strongly depends on the S content at the absorber surface. The associated modification of the heterojunction partners has significant impact on the electronic structure at the interface.