Intrinsic Point Defects in Inorganic Cesium Lead Iodide Perovskite CsPbI3

• Published in: Journal of physical chemistry. C Vol. 122; no. 2; pp. 1345 - 1350
• Main Authors: Huang, Yang, Yin, Wan-Jian, He, Yao
• Format: Journal Article
• Language: English
• Published: American Chemical Society 18.01.2018
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.7b10045

Cesium lead iodide (CsPbI3) has recently emerged as a promising solar photovoltaic absorber. However, the cubic perovskite (α-phase) remains stable only at high temperature and reverts to a photoinactive nonperovskite (δ-phase) CsPbI3 at room temperature. In this work, the formation energies and transition energy levels of intrinsic point defects in γ- (more stable than α-phase) and δ-phases have been studied systematically by first-principles calculations. It is found that CsPbI3 exhibits a unipolar self-doping behavior (p-type conductivity), which is in contrast to CH3NH3PbI3. Most of the intrinsic defects induce deeper transition energy levels in δ-phase than in γ-phase. This is due to the small Pb–I–Pb bond angles in δ-phase that results in the weak antibonding character of valence band maximum (VBM). However, the strong antibonding character of VBM plays a critical role in keeping defect tolerance in semiconductors. Therefore, these results indicate the importance of the large metal–halide–metal bond angle for the performance of perovskite solar cells.