Nam-Gyu Park1
Sungkyunkwan University1
Since the seminal work on a 9.7% efficient solid-state perovskite solar cell in 2012, its power conversion efficiency (PCE) reached over 25% within a decade. Although PSCs demonstrated a high PCE comparable to silicon solar cells, stability is still the remaining issue. In order to improve substantially the stability of PSCs, perovskite materials and interfaces should be carefully manipulated. In this talk, the importance of crystal facets and interfaces is emphasized in improving stability. We found that moisture stability depends on crystal facets. Among the three facets of (100), (110) and (111) in FAPbI<sub>3</sub> film, the (100) facet was found to be unstable but the (111) facet was quite stable under moisture. Experimental combined with theoretical studies revealed that a crystal facet with moisture instability provided a strong water adhesion via the hydroxylation of Pb atoms, leading to phase transformation. Perovskite films with abundant moisture-tolerant (111) facets were successfully prepared via additive engineering, which showed exceptional stability against moisture without additional surface passivation. A buried interface with homojunction was found to play a critical role in the stability of PSCs. A band alignment via interface engineering led to leveling off the work function at the homojunction, which improved stability significantly.