Qiao Lu, Fang Wei-Hai, Prezhdo Oleg V, Long Run
College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing 100875, People's Republic of China.
Department of Chemistry, University of Southern California, Los Angeles, California 90007, United States.
J Am Chem Soc. 2022 Mar 30;144(12):5543-5551. doi: 10.1021/jacs.2c00319. Epub 2022 Mar 16.
Exposure to oxygen undermines stability and charge transport in metal halide perovskites, because molecular oxygen, as well as photogenerated superoxide and peroxide, erodes the perovskite lattice and creates charge traps. We demonstrate that alkaline earth metals passivate the oxygen species in CHNHPbI by breaking the O-O bond and forming new bonds with the oxygen atoms, shifting the trap states of the antibonding O-O orbitals from inside the bandgap into the bands. In addition to eliminating the oxidizing species and the charge traps, doping with the alkaline earth metals slightly increases the bandgap and partially localizes the electron and hole wavefunctions, weakening the electron-hole and charge-phonon interactions and making the charge carrier lifetimes longer than even those in pristine CHNHPbI. Relative to CHNHPbI exposed to oxygen and light, the charge carrier lifetime of the passivated CHNHPbI increases by 2-3 orders of magnitude. The ab initio quantum dynamics simulations demonstrate that alkaline earth metals passivate efficiently not only intrinsic perovskite defects, but also the foreign species, providing a viable strategy to suppress perovskite degradation.
暴露于氧气会破坏金属卤化物钙钛矿的稳定性和电荷传输，因为分子氧以及光生超氧化物和过氧化物会侵蚀钙钛矿晶格并产生电荷陷阱。我们证明，碱土金属通过打破O-O键并与氧原子形成新键来钝化CHNHPbI中的氧物种，将反键O-O轨道的陷阱态从带隙内转移到能带中。除了消除氧化物种和电荷陷阱外，用碱土金属掺杂还会略微增加带隙，并部分使电子和空穴波函数局域化，减弱电子-空穴和电荷-声子相互作用，并使电荷载流子寿命甚至比原始CHNHPbI中的寿命更长。相对于暴露于氧气和光的CHNHPbI，钝化后的CHNHPbI的电荷载流子寿命增加了2-3个数量级。从头算量子动力学模拟表明，碱土金属不仅能有效地钝化钙钛矿的固有缺陷，还能钝化外来物种，为抑制钙钛矿降解提供了一种可行的策略。
