Vigil Julian A, Wolf Nathan R, Slavney Adam H, Matheu Roc, Saldivar Valdes Abraham, Breidenbach Aaron, Lee Young S, Karunadasa Hemamala I
Department of Chemistry, Stanford University, Stanford, California 94305, United States.
Department of Chemical Engineering, Stanford University, Stanford, California 94305, United States.
ACS Cent Sci. 2024 Apr 2;10(4):907-919. doi: 10.1021/acscentsci.4c00056. eCollection 2024 Apr 24.
The response of an oxide crystal to the atmosphere can be personified as breathing-a dynamic equilibrium between O gas and O anions in the solid. We characterize the analogous defect reaction in an iodide double-perovskite semiconductor, CsSnI. Here, I gas is released from the crystal at room temperature, forming iodine vacancies. The iodine vacancy defect is a shallow electron donor and is therefore ionized at room temperature; thus, the loss of I is accompanied by spontaneous -type self-doping. Conversely, at high I pressures, I gas is resorbed by the perovskite, consuming excess electrons as I is converted to 2I. Halide mobility and irreversible halide loss or exchange reactions have been studied extensively in halide perovskites. However, the reversible exchange equilibrium between iodide and iodine [2I ↔ I + 2e] described here has often been overlooked in prior studies, though it is likely general to halide perovskites and operative near room temperature, even in the dark. An analysis of the 2I/I equilibrium thermodynamics and related transport kinetics in single crystals of CsSnI therefore provides insight toward achieving stable composition and electronic properties in the large family of iodide perovskite semiconductors.
氧化物晶体对大气的响应可以拟人化为呼吸——即固体中氧气气体与氧阴离子之间的动态平衡。我们描述了碘化物双钙钛矿半导体CsSnI中类似的缺陷反应。在这里，碘气体在室温下从晶体中释放出来，形成碘空位。碘空位缺陷是一种浅电子施主，因此在室温下会被电离；因此，碘的损失伴随着自发的n型自掺杂。相反，在高碘压力下，碘气体被钙钛矿重新吸收，在碘转化为2I时消耗多余的电子。卤化物迁移率以及不可逆的卤化物损失或交换反应在卤化物钙钛矿中已得到广泛研究。然而，这里描述的碘化物与碘之间的可逆交换平衡[2I ↔ I + 2e]在先前的研究中常常被忽视，尽管它可能在卤化物钙钛矿中普遍存在，并且即使在黑暗中在室温附近也起作用。因此，对CsSnI单晶中2I/I平衡热力学和相关输运动力学的分析有助于深入了解如何在大型碘化物钙钛矿半导体家族中实现稳定的组成和电子性质。
