Low temperature growth (001) facet-oriented p-type FAPbI₃ perovskite solar cells

Various atomic arrangements and coordination of facets significantly influence the photoelectric properties of perovskites. When preparing FAPbI₃ 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 FAPbI₃ are greatly promoted without the presence of other crystal planes attributed to the formation of 2D PEA₂FA_n-1Pb_nI_3n+1. This enhancement in the crystallographic orientation of FAPbI₃ 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 V_oc of 1.19 V.