Chalcopyrite ternary and kesterite quaternary thin films, such as Cu (In,Ga)(S,Se)2and Cu2ZnSn (S,Se)4generically referred to as CIGSSe and CZTSSe, respectively, have become the subject of considerable interest and study for semiconductor devices in recent years [1,2]. These materials are of particular interest for use as an absorber layer in photovoltaic devices. In thin film solar cells, the p-type CIGSSe or CZTSSe layer is combined with an n-type semiconductor thin film such as CdS buffer layer to form the p-n heterojunction of the device. The synthesis process of the CIGSSe or CZTSSe absorber layer requires temperatures ranging between 400 and 600 °C to form the photoactive chalcopyrite or kesterite phases [3,4]. During the synthesis process, the formation of trace amounts of binary/ternary compositions (i.e., undesirable secondary or impurity phases consisting of selenides, oxides, carbonates, etc.) may occur. These trace amounts of impurity phases may form at the nascent absorber surfaces, which could negatively affects the photovoltaic conversion efficiencies of solar cells [5-7]. Therefore, prior to the deposition of the CdS buffer layer, there is a need to clean the CIGSSe or CZTSSe surfaces to remove any possible traces of such impurities.
Effect of Prefabricated Layer Structure on Properties of CZTS Thin Films and Solar Cells
