Enhanced perovskite crystallinity via short-term ultraviolet irradiation

Despite the recent rapid development in the organic–inorganic halide perovskite solar cells (PSCs), the crystalline stability of the perovskite (PVK) material, particularly of the MAPbI3, remains a significant impediment to PSC applications. We proposed that short-term ultraviolet (UV) irradiation under air conditions can stabilize the PVK phase and increases the film crystallinity. Detailed investigations indicated that the electrons can be released from the bridging hydroxyls (OHB) bonds under UV irradiation to generate a small amount of active oxygen (O2−) on the TiO2 film surface, forming stable Pb–O bonds and α phase PVK. A 25% increases in photovoltaic conversion efficiency with a considerable stability, and the device maintains over 90% efficiency after 400 h of storage in N2. This study provides a simple and effective method to produce efficient and stable PSC devices at low cost.