Evidence of tunable macroscopic polarization in perovskite films using photo-Kelvin Probe Force Microscopy

Using photo-Kelvin Probe Force Microscopy (photo-KPFM) we observed macroscopic, photo-induced polarization through 200 nm thick polycrystalline methylammonium lead triiodide (MAPbI3) perovskite films in MAPbI3/charge carrier transport material (CTM) bilayers. A polarization of up to ∼600 mV was observed for some MAPbI3/CTM bilayers and the sign of polarization is dependent on the predominant charge carrier properties of the CTM used. We propose that through-film photo-KPFM polarization measurements can be useful in determining the efficacy of a CTM. Polarized perovskite films may also have applications as surfaces for performing electrochemical reactions.