@misc{BaerSongCaballeroetal., author = {B{\"a}r, Marcus and Song, X. and Caballero, R. and Duarte, Roberto Felix and Gerlach, Dominic and Kaufmann, Christian and Schock, Hans-Werner and Wilks, Regan G.}, title = {Na incorporation into Cu(In,Ga)Se2 thin-film solar cell absorbers deposited on polyimide: Impact on the chemical and electronic surface structure}, series = {Journal of Applied Physics}, volume = {111}, journal = {Journal of Applied Physics}, number = {3}, issn = {1089-7550}, pages = {034903}, abstract = {Na has deliberately been incorporated into Cu(In,Ga)Se2 ("CIGSe") chalcopyrite thin-film solar cell absorbers deposited on Mo-coated polyimide flexible substrates by adding differently thick layers of NaF in-between CIGSe absorber and Mo back contact. The impact of Na on the chemical and electronic surface structure of CIGSe absorbers with various Cu-contents deposited at comparatively low temperature (420 °C) has been studied using x-ray photoelectron and x-ray excited Auger electron spectroscopy. We observe a higher Nasurface content for the Cu-richer CIGSe samples and can distinguish between two different chemical Na environments, best described as selenide-like and oxidized Na species, respectively. Furthermore, we find a Cu-poor surface composition of the CIGSe samples independent of Na content and — for very high Na contents — indications for the formation of a (Cu,Na)-(In,Ga)-Se like compound. With increasing Nasurface content, also a shift of the photoemission lines to lower binding energies could be identified, which we interpret as a reduction of the downward band bending toward the CIGSe surface explained by the Na-induced elimination of InCu defects.}, language = {en} }