A New Descriptor for Complicated Effects of Electronic Density of States on Ion Migration

Halide perovskites have attracted much attention because of their excellent optoelectronic properties, such as high light absorption, long carrier diffusion length, and high defect tolerance. Ion migration induced device performance degradation, which is not yet fully understood, has become the key obstacle for commercialization of halide perovskites. Here, a general mechanism is proposed, which can build up the connection between the ion migration barrier and the electronic density of states, to clarify the origin of low barrier for ion migration. Density functional theory (DFT) simulation results show that the low barrier is caused by a significant energy difference in band centers between Pb2+ and the isolating halogen anion or by the small number of density of states. Following the explored mechanism, two strategies are proposed to boost barriers via DFT combination CI-NEB simulations: 1) halide double perovskites and 2) B-site doping. Furthermore, the finding not only deepens the understanding of ion migration in halide perovskites but also paves a new path for the commercialization of halide perovskite optoelectronic devices.