Electron–Phonon Coupling-Mediated Ultralong Carrier Lifetime in an All-Inorganic Two-Dimensional Cs<sub>2</sub>PbI<sub>2</sub>Cl<sub>2</sub> Perovskite: Explanation for the High Antisite Defect Tolerance
Xingyun Luo, Xiaoji Zhao, Xiaoji Zhao, Xian Zhao, Xian Zhao, Yanlu Li
Abstract
Two-dimensional (2D) halide perovskite are appealing candidates for applications in optoelectronics and photovoltaics, but their energy conversion efficiency is severely limited by nonradiative electron–hole recombination. In most investigations, point defects with deep defect levels and deep charge-state transition levels in the band gap are treated as the carrier recombination centers. For the all-inorganic 2D Css 2 PbI 2 Cl 2, the I Pb antisite defect is the most likely to form and cause nonradiative electron–hole recombination. By using density functional theory and ab initio nonradiative molecular dynamics calculations, we found that the I Pb defect can introduce the deep acceptor and donor levels into the band gap. Because electron–phonon coupling gives rise to weak nonadiabatic coupling and rapid loss of electronic coherence, those levels lead to a reduction of the carrier loss and the prolongation of the excited-state carrier lifetime, thereby enhancing the photoelectric and defect tolerance properties of the Cs 2 PbI 2 Cl 2 material. These results could deepen the understanding of the chemistry of defects and carrier dynamics in perovskite materials.