Correctly Assessing Defect Tolerance in Halide Perovskites

The notion of "defect tolerance" has often been invoked to explain the excellent performance of halide perovskites in optoelectronic applications. However, this concept has not been rigorously defined or assessed. A common interpretation is that all of the energetically favorable intrinsic defects are shallow. On the basis of examples in the prototypical halide perovskite CsPbI3, we show that this is not the case. The antisite defects PbI and IPb are energetically favorable, but also have levels deep in the band gap. Still, because of strong anharmonicity, they are not efficient nonradiative recombination centers. Our study demonstrates how to correctly evaluate the "defect tolerance" of halide perovskites.