Correlating Photoluminescence Heterogeneity with Local Electronic Properties in Methylammonium Lead Tribromide Perovskite Thin Films

We conduct correlated laser scanning confocal photoluminescence (PL) microscopy, scanning kelvin probe microscopy, and conductive atomic force microscopy (c-AFM) to understand the origins and effects of local heterogeneity in films of the hybrid organic–inorganic perovskite semiconductor methylammonium lead tribromide (MAPbBr₃). We compare PL between perovskite films deposited on glass and on hole-transporting contacts. In both systems, we observe heterogeneous PL, but this heterogeneity is due to different mechanisms. On glass substrates, we observe that the PL maps are dominated by lateral carrier diffusion, and on hole-transporting contacts, we observe an anticorrelation between PL and local hole injected current as measured by c-AFM. We conclude that the local variations are due to heterogeneous electronic coupling at the perovskite–electrode interface. We also show that correlated PL and AFM studies are expected to play a key role in studying the electronic heterogeneities in the perovskite itself, which are currently screened by the perovskite–contact interfaces. Our results suggest the need for new selective contacts to improve the charge transfer at the perovskite–contact interfaces