Segregation of Native Defects to the Grain Boundaries in Methylammonium Lead Iodide Perovskite.
Weitao ShanWissam A SaidiPublished in: The journal of physical chemistry letters (2017)
Native point and grain boundary (GB) defects are ubiquitous in methylammonium lead iodide (MAPbI3) sensitizers employed in solar cells that are polycrystalline in nature. Here we use density functional theory (DFT) in conjunction with a thermodynamic approach to determine the stability and electronic properties of all native point defects and their interplays with Σ5-(210) GB in MAPbI3. The transition levels of charged defects are investigated with inclusion of electrostatic charge corrections and spin-orbit coupling. We find that the GB region is a sink for most of the native point defects under different synthesis conditions. For the crystalline and bicrystalline MAPbI3 with Σ5-(210) GB, we find respectively that the p-type antisite defects MAI and PbI, where I substitutes for MA or Pb, introduce deep levels, and both are relatively stable under I-rich conditions. Hence, I-poor conditions are more preferable for synthesis of MAPbI3 to have defects with electronically benign character.