@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} } @misc{GerlachWipplerWilksetal., author = {Gerlach, Dominic and Wippler, David and Wilks, Regan G. and Wimmer, Manuel and Lozac'h, Micka{\"e}l and Duarte, Roberto Felix and Ueda, Shigenori and Yoshikawa, Hideki and Lips, Klaus and Rech, Bernd and Sumiya, Masatomo and Kobayashi, Kaoru and Gorgoi, Mihaela and H{\"u}pkes, J{\"u}rgen and B{\"a}r, Marcus}, title = {p-Type a-Si:H/ZnO:Al and μc-Si:H/ZnO:Al Thin-Film Solar Cell Structures—A Comparative Hard X-Ray Photoelectron Spectroscopy Study}, series = {IEEE journal of photovoltaics}, volume = {3}, journal = {IEEE journal of photovoltaics}, number = {1}, issn = {2156-3381}, pages = {483 -- 487}, abstract = {The chemical and electronic properties of a- Si:H(B)/ZnO:Al and μc-Si:H(B)/ZnO:Al thin-film solar cell structures are studied by hard X-ray photoelectron spectroscopy (HAXPES). Using a combination of different X-ray excitation energies and deliberate sample design, we were able to select the probed volume, i.e., the silicon capping layer only or the silicon and zinc oxide layer (including the buried interface). For the a-Si:H(B) material, we find a higher deposition rate and a smaller value for the modified Auger parameter than for μc-Si:H(B). In addition, we find indications of a pronounced band bending limited to the very surface of the a-Si:H(B) and the μc-Si:H(B) layers, which is more distinct in the latter case.}, language = {en} } @misc{BaerTheisenWilksetal., author = {B{\"a}r, Marcus and Theisen, J.-P. and Wilks, Regan G. and Erfurth, Felix and Duarte, Roberto Felix and Gerlach, Dominic and Haas, S. and Tati-Bismaths, L. and Reinert, F. and Kronast, F. and Niesen, T. P. and Palm, J{\"o}rg and Visbeck, Sven and Weinhardt, Lothar}, title = {Lateral inhomogeneity of the Mg/(Zn+Mg) composition at the (Zn,Mg)O/CuIn(S,Se)2 thin-film solar cell interface revealed by photoemission electron microscopy}, series = {Journal of Applied Physics}, volume = {113}, journal = {Journal of Applied Physics}, number = {19}, issn = {1520-8850}, doi = {10.1063/1.4804413}, pages = {193709}, abstract = {Spatial variations in the chemical composition of the (Zn,Mg)O/CuIn(S,Se)2 thin-film solar cell interface were studied by photoemission electron microscopy (PEEM). Energy filtered PEEM images indicate significant differences in the magnesium and zinc distribution. Local photoemission measurements reveal a relative difference in the derived Mg/(ZnþMg) composition of the (Zn,Mg)O material of up to (11.460.7)\%, which can be expected to induce band gap fluctuations of (60630) meV. Furthermore, local areas with significant accumulations of sodium could be observed.}, language = {en} } @misc{GorgoiGerlachWilksetal., author = {Gorgoi, Mihaela and Gerlach, Dominic and Wilks, Regan G. and Wippler, David and Wimmer, Manuel and Lozac'h, Micka{\"e}l and Duarte, Roberto Felix and M{\"u}ck, Leonie Anna and Meier, M. and Ueda, Shigenori and Yoshikawa, Hideki and Lips, Klaus and Rech, Bernd and Sumiya, Masatomo and H{\"u}pkes, J{\"u}rgen and Kobayashi, Kaoru and B{\"a}r, Marcus}, title = {The silicon/zinc oxide interface in amorphous silicon-based thin-film solar cells: Understanding an empirically optimized contact}, series = {Applied Physics Letters}, volume = {103}, journal = {Applied Physics Letters}, number = {2}, issn = {1077-3118}, pages = {023903}, abstract = {The electronic structure of the interface between the boron-doped oxygenated amorphous silicon "window layer" (a-SiOx:H(B)) and aluminum-doped zinc oxide (ZnO:Al) was investigated using hard x-ray photoelectron spectroscopy and compared to that of the boron-doped microcrystalline silicon (μc-Si:H(B))/ZnO:Al interface. The corresponding valence band offsets have been determined to be (-2.87 ± 0.27) eV and (-3.37 ± 0.27) eV, respectively. A lower tunnel junction barrier height at the μc-Si:H(B)/ZnO:Al interface compared to that at the a-SiOx:H(B)/ZnO:Al interface is found and linked to the higher device performances in cells where a μc-Si:H(B) buffer between the a-Si:H p-i-n absorber stack and the ZnO:Al contact is employed.}, language = {en} } @phdthesis{Gerlach, author = {Gerlach, Dominic}, title = {Surface and interface characterization of thin-film silicon solar cell structures}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-28254}, pages = {128}, language = {en} } @misc{WipplerWilksPietersetal., author = {Wippler, David and Wilks, Regan G. and Pieters, Bart E. and Albada, Sacha Jennifer van and Gerlach, Dominic and H{\"u}pkes, J{\"u}rgen and B{\"a}r, Marcus and Rau, Uwe}, title = {Pronounced surface band bending of thin-film silicon revealed by modeling core levels probed with hard x-rays}, series = {ACS Applied Materials \& Interfaces}, volume = {8}, journal = {ACS Applied Materials \& Interfaces}, number = {27}, issn = {1944-8252}, doi = {10.1021/acsami.6b04666}, pages = {17685 -- 17693}, language = {en} }