Effect of combined treatment of cesium fluoride as precursor and post-treatment on Cu(In,Ga)Se2 thin film solar cell

In this study, we investigate the combined effect of cesium fluoride (CsF) as a precursor and post-treatment on a Cu(Inx,Ga1-x)Se2 (CIGS) thin film solar cell fabricated onto sodalime glass substrates. The combined treatment improves the open-circuit voltage, fill factor, and cell efficiency of the solar cell compared with its single counter treatment. Secondary ion mass spectroscopy measurements show a higher concentration of Cs diffusion in the surface regions in the combined treatment, which change the electronic properties of the buffer/CIGS interface by reducing interfacial recombination. Solar cells fabricated using CsF as a precursor indicate a deterioration in device performance owing to the formation of bulk defects, as confirmed from admittance spectroscopy. This study unveils device performance improvement by combining a heavy alkali metal as a precursor and post-treatment on CIGS thin film solar cells.