Atomic-scale understanding on the physics and control of intrinsic point defects in lead halide perovskites

Lead halide perovskites (LHPs) have attracted considerable attention as promising materials for photovoltaic and optoelectronic applications. Intrinsic point defects play an important role in determining the performance of semiconductor devices. LHPs exhibit strong ionic character and unique electronic structure; thus, their defect properties are quite different from conventional covalent bond semiconductors. Understanding the defect science is crucial to the performance optimization of LHP-based devices. State-of-the-art first-principles calculation methods enable one to explore atomistic mechanisms of various defect-related processes, and tremendous efforts from theoretical simulations have provided invaluable insights to the defect physics and defect control of LHPs. In this review, we summarize recent progress, made with the help of theoretical modeling, on atomic-scale understanding about intrinsic point defects and related processes in LHPs. The fundamental properties of intrinsic point defects in LHPs are first introduced, including defect formation energy, charge transition level, and defect tolerance and its origin. A particular emphasis is given to the effects of band edge position on calculated defect properties. The impact of these defects on structural properties, carrier dynamics, and photoluminescence of LHPs is then presented. Advanced strategies to engineer the defects in LHPs are also reviewed, such as growth condition, defect passivation, and doping. Finally, we discuss open issues and outline directions toward a better understanding of defects of LHPs from a theoretical perspective. The goal of the review is to provide a comprehensive summary of atomic-scale understanding of intrinsic point defects in LHPs and to help further related research in the perovskite community.