First-principles Study of Intrinsic and Extrinsic Point Defects in Lead-Based Hybrid Perovskites

Intrinsic and extrinsic defects play a major role in determining solar cell efficiencies of lead halide hybrid perovskite absorbers. Here, we present the results of first-principles computations performed on MAPbBr 3 (MA= methylammonium) to study the energetics and defect levels of intrinsic point defects, namely vacancy, self-interstitial and anti -site, and extrinsic Pbsubstitution defects. While vacancies are the lowest formation energy intrinsic defects and create shallow transition levels, a number of extrinsic defects can have comparable formation energies under desirable chemical potential conditions. Therefore, carrier concentrations may be tunable with these substituents. Further, some extrinsic defects create deeper transition levels which can potentially be exploited to enhance solar cell efficiencies via sub-gap absorption.