Low temperature growth (001) facet-oriented p-type FAPbI perovskite solar cells.

Various atomic arrangements and coordination of facets significantly influence the photoelectric properties of perovskites. When preparing FAPbI with a (001) crystal facet, the presence of other crystal facets such as (011) or (111) can adversely affect the carrier extraction efficiency and device stability. In this study, the desired (001) orientations of FAPbI are greatly promoted without the presence of other crystal planes attributed to the formation of 2D PEAFAPbI. This enhancement in the crystallographic orientation of FAPbI concurrently enabled a transition in its conductivity type from n-type to p-type. Furthermore, our DFT results revealed that the holes in the (001) facet exhibit superior carrier transport properties in FA-based perovskites. As a result, the devices show a power conversion efficiency of 23.02% with a of 1.19 V.