Insight into the Improved Phase Stability of CsPbI3 from First-Principles Calculations

The effect of organic cation doping with aziridinium (Az+) on the material properties of CsPbI3 was investigated by applying first-principles calculations. The results showed that the phase stability is greatly improved by incorporating the organic cation Az+ at the A site of CsPbI3. However, the band gap of CsPbI3 is further enlarged from 1.76 to 2.27 eV when 12.5% of Az doping is used. The optical absorption coefficient of Cs0.875Az0.125PbI3 is also decreased in the visible light region. The reasons of the improved phase stability and the enlargement of band gap arising from the organic cation doping are revealed. Our calculated results can provide theoretical guidance for improving the phase stability of halide perovskites.