Surface and Interface Characterization by X ray and Electron Spectroscopies Revealing the Peculiarities of Cu In,Ga Se2 Chalcopyrite and CH3NH3PbI 3 x Clx Perovskite based Thin Film Solar Cell Structures

This thesis focuses on the investigation and characterization of the surfaces and interfaces of chalcopyrite based Cu In,Ga Se2 CIGSe and organo metal mixed halide perovskites, specifically CH3NH3PbI 3 x Clx thin film solar cell absorbers using various x ray and electron spectroscopies. In particular, the impact of alkali treatments on the chemical and electronic surface and near surface structure of CIGSe absorbers is studied. For CH3NH3PbI 3 x Clx the compound formation is monitored and the peculiarities of the interface formation of CH3NH3PbI 3 x Clx on compact and mesoporous TiO2 are examined. Laboratory and synchrotron based photoelectron spectroscopy are used to gain a depth dependent picture of the chemical and electronic structure in the surface and near surface region of CIGSe absorbers, focusing on the influence of NaF and NaF KF post deposition treatments PDT when compared to alkali free CIGSe absorbers. The alkali free and NaF PDT absorbers show similar chemical properties, having a Cu and Ga poor surface region compared to the nominal bulk and the same chemical environment for indium and selenium. For the NaF KF PDT samples a K In Se compound is present on top of a Cu In Ga Se compound, with a nanopatterned surface. The NaF KF PDT has a surface regionthat is almost devoid of Cu and Ga. Further, for the NaF PDT sample a near surface electronic band gap of ?? eV is derived. In contrast, a large and more gradual change towards the surface is obtained for the NaF KF PDT absorber with exhibiting a significant band gap widening of the surface, which is ascribed in agreement withto a Cu and Ga devoid surface region and the formation of a K In Se surface compound. To in situ monitor the compound formation of CH3NH3PbI 3 x Clx on compact TiO2 c TiO2 hard x ray photoelectron spectroscopy is used. While During in situ annealing a drop casted layer of precursor solution on c TiO2 shifts in the perovskite related core levels can be observed upon reach during the transition temperature of 80 100 C are observed. ...