Are hybrid perovskites really defect tolerant?

In recent years, great effort has been devoted to deducing the fundamental mechanisms that enable the high efficiency of hybrid perovskites. One widely accepted proposition is that, while high concentrations of point defects are present in hybrid perovskites, these defects do not cause nonradiative recombination; hence the concept of “defect tolerance”. We explicitly calculate the defect-assisted nonradiative recombination rates in the prototypical hybrid perovskite MAPbI₃ (MA=CH₃NH₃) with the multiphonon emission methodology. To achieve accurate and reliable results, all of our first-principles calculations are based on hybrid density functional theory with spin-orbit coupling included. We show that hybrid perovskites actually do suffer from defect-assisted recombination, i.e., they are not “defect tolerant”. The iodine interstitial is a strong nonradiative recombination center, and is likely responsible for the experimentally observed nonradiative recombination rates. These insights should put an end to misguided attempts to analyze and design device characteristics based on erroneous assumptions, and point to the actual fruitful directions of defect engineering toward improved efficiencies.