Optimization of Cd2+ partial electrolyte treatment on the absorber layer for high-efficiency Cu2ZnSnSe4 solar cells

Currently, many researchers are focused on promising new energy technologies such as Cu2ZnSnS4-based solar cells to replace fossil fuel sources. Investigations into a variety of methods have been done to analyze the interfacial problems and improve the cell interfacial properties via a variety of methods. In particular, In order to improve the electrical performance of Cu2ZnSnSe4 (CZTSe) based solar cells, the Cd partial electrolyte (Cd PE) treatment that is an effective method in CIGS solar cells prior to applying their CdS buffer layer to their absorber layer has been studied. In our study, we investigated the Cd PE treatment time, the Cd PE bath temperature, and the correlation between Cd PE treatment and CdS thickness. The optimum Cd PE absorber treatment was 7min at 70°C, with a CdS layer of 35nm thick deposited cells. This combination increased photo-carrier collection in the short wavelength range and reduced absorber-buffer interface recombination. The efficiency of a 35nm buffer layer sample without PE treatment was 8.90%. The efficiency of another 35nm buffer layer sample was 10.38% (Voc: 441mV, Jsc: 38.15mA/cm2, and FF: 61.58%) after Cd PE treatment due to the increase of Jsc, FF and Rs despite the deficit of Voc.