P-N junction passivation in kesterite solar cells by use of solution processed TiO2 layer

In this work, we used a solution processed TiO2 layer between Cu2ZnSnSe4 and CdS buffer layer to reduce the recombination at the p-n junction. Introducing the TiO2 layer showed a positive impact on VOC but fill factor and efficiency decreased. Using a KCN treatment, we could create openings in the TiO2 layer, as confirmed by transmission electron microscopy measurements. Formation of these openings in the TiO2 layer led to the improvement of the short circuit current, fill factor and the efficiency of the modified solar cells.