Creation and Annihilation of Nonradiative Recombination Centers in Polycrystalline Metal Halide Perovskites by Alternating Electric Field and Light

Metal halide perovskites are promising optoelectronic materials. Their electronic properties however are rather unstable which is often assigned to ion migration. Ion migration can be readily influenced by an electric field (EF). Here, the response of photoluminescence (PL) of individual MAPbX₃ (MA = CH₃NH₃, X = I, Br) sub-micrometer-sized polycrystals to EF is studied. Alternating EF with frequency higher than 10 Hz is found to reversibly quench PL. It is proposed that an alternating EF when applied together with light increases ion migration. This leads to a shift in the equilibrium between creation and annihilation of defects toward higher concentration of nonradiative recombination centers. The PL quenching is found to increase with increasing frequency of the field. This can be rationalized by the frequency dependence of the dielectric constant, leading to stronger internal fields for high modulation frequencies compared to, e.g., a constant EF with the same external amplitude. PL quenching and enhancement observed under constant EF are hypothesized to be due to a reconfiguration of already existing nonradiative recombination centers situated on grain boundaries. The control of perovskite PL by alternating EF reported here can find applications in optoelectronic devices.