Incorporation of chloride species in the perovskite precursor solution is one of the effective strategies to obtain highly crystalline perovskite films toward efficient solar cell performance. Although chloride atoms are considered to play an important role in crystallization their effect has not been fully investigated yet. In this study, the effect of chloride atoms in perovskite intermediate phase is studied using molecular modeling and simulations. The calculation validated the fact that the specific lattice plane with chloride atoms in the structure resulted in the lower growth rate compared to that of the conventional perovskite intermediate phase.

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.