The Interaction of Ion Migration with Shockley-Read-Hall Recombination in the Bulk of Perovskite Solar Cells Explains Anomalous Voltage and Luminescence Transients

Slow transient responses in perovskite solar cells have been attributed to a range of possible mechanisms, but the migration of ionic charge is a leading candidate. In this paper, we present an overview of the results of a transient numerical model of drift-diffusion in a semiconductor device, to which we add mobile ionic charge, to demonstrate that a range of monotonic and non-monotonic transient voltage and luminescence responses described in the perovskite literature can be replicated with the movement on ionic charge. These include some unusual non-monotonic responses that have previously been attributed to multiple, competing mechanisms. We observe that the key mechanism instead is the interaction of the ionic charge on the distribution of electrons and holes and a subsequent change in the distribution of trap-mediated recombination that is modelled after Shockley-Read-Hall statistics. These results are evidence for the value of a rigorous computation of the interaction of ion migration and traditional semiconductor charge transport models to reveal interactions between ion migration and recombination in perovskite solar cells that might otherwise escape our intuition.