Abstract
We synthesized two types of MAPbI3 single-crystal films with dominant (001) and (100) surface orientations for solar cells. We found that both MAPbI3 (001) and (100) single-crystal films have efficient hole transfer into poly(triaryl)amine (PTAA), as evident from the reduced photoluminescence (PL) intensity and lifetime, as well as the type-II energy alignment. Unlike a MAPbI3 (100) single-crystal film with a strong PL quenching due to efficient electron transfer to phenyl-C61-butyric acid methyl ester (PCBM), the MAPbI3 (001) single-crystal film exhibits an increase in PL intensity in the presence of PCBM, which can be attributed to surface passivation. Interestingly, different from the conventional MAPbI3 (100) that suffers from a significant decrease in the PCE (from 19.3 to 14.4%), the MAPbI3 (001) single-crystal film shows an increase in the PCE (from 16.0 to 17.2%) and much better stability under ambient conditions thanks to the dual passivation on the PbI2-rich surface by PCBM and O2.