Unravelling the role of vacancies in lead halide perovskite through electrical switching of photoluminescence.

We address the behavior in which a bias voltage can be used to switch on and off the photoluminescence of a planar film of methylammonium lead triiodide perovskite (MAPbI3) semiconductor with lateral symmetric electrodes. It is observed that a dark region advances from the positive electrode at a slow velocity of order of 10 μm s-1. Here we explain the existence of the sharp front by a drift of ionic vacancies limited by local saturation, that induce defects and drastically reduce the radiative recombination rate in the film. The model accounts for the time dependence of electrical current due to the ion-induced doping modification, that changes local electron and hole concentration with the drift of vacancies. The analysis of current dependence on time leads to a direct determination of the diffusion coefficient of iodine vacancies and provides detailed information of ionic effects over the electrooptical properties of hybrid perovskite materials.