Origin of Enhanced Nonradiative Carrier Recombination Induced by Oxygen in Hybrid Sn Perovskite
Yuhang Liang, Xiangyuan Cui, Feng Li, Catherine Stampfl, Simon P. Ringer, Xudong Yang, Jun Huang, Rongkun Zheng
Abstract
Oxygen ingression has been shown to substantially decrease the carrier lifetime of Sn-based perovskites, behind which the mechanism remains yet unknown. Our first-principles calculations reveal that in prototypical MASnI 3 (MA = CH 3 NH 3 ), oxygen by itself is not a recombination center. Instead, it tends to form substitutional O I through combining with native I vacancies (V I ) and remarkably increases the original recombination rate of V I by 2–3 orders of magnitude. This rationalizes the experimentally observed sharp decline of carrier lifetime in perovskites exposed to air. The significantly enhanced carrier recombination is due to a smaller electron capture barrier of O I, resulting from lattice strengthening and the suppressed structural relaxation upon electron capture. These insights offer a route to further improve device performance via anion engineering in broad Sn-based perovskite optoelectronics operating in ambient air. Moreover, our results highlight the important role of lattice relaxation for nonradiative carrier capture in materials in general.