Effect of UV-ozone treatment for KCl interlayer in perovskite solar cells

The performance of perovskite solar cells (PSCs) is significantly governed by the interface of perovskite layer. Therefore, a great deal of attention has been paid to the interface engineering of perovskite layer to improve the performance of PSC. In the meantime, KCl is one of the popular molecules being utilized for the interface treatment between SnO₂ and perovskite. In this study, we investigate the effect of UV-ozone (UVO) treatment of KCl interlayer on the photovoltaic performance. A device employing UVO-treated KCl shows a higher power conversion efficiency mainly based on an increased open-circuit voltage (V_OC). Ultraviolet photoelectron spectroscopy analysis indicates that the UVO treatment induces a rearrangement of energy level at the interface, being responsible for the increase in V_OC. Accordingly, an increased charge recombination resistance is evidenced by impedance spectroscopy owing to the inhibited recombination at the SnO₂ and perovskite interface by the aid of the aligned energy level.