Impact of Compact TiO2 Interface Modification on the Crystallinity of Perovskite Solar Cells

The effect of TiO2 interfacial morphology on perovskite crystallinity was investigated by modifying the micro and nanoscale surface roughness of compact TiO2. The surface treatment of compact TiO2 layer is considered as an effective strategy to improve a photovoltaic performance of perovskite solar cells although there is little discussion about the crystallinity of perovskite on top of TiO2. In this research, we have examined the impact of micro and nano scale surface roughness and its influence on perovskite crystal as well as the device performance. Surprisingly, while any noticeable voids were not observed at the interface between the compact TiO2 and perovskite layer, the morphology of the perovskite crystal showed a remarkable improvement by either the micro or nano scale interfacial modification and eventually resulted in an enhancement in photoconversion efficiency and I-V hysteresis. This result pointed out the importance of an underlayer surface morphology in perovskite crystallization process and the possibility that grain boundaries existing in perovskite layer may also be a factor affecting I-V hysteresis in perovskite solar cells.