Anaya Miguel, Galisteo-López Juan F, Calvo Mauricio E, Espinós Juan P, Míguez Hernán
Instituto de Ciencia de Materiales de Sevilla, Consejo Superior de Investigaciones Científicas-Universidad de Sevilla , C/Américo Vespucio 49 , 41092 Sevilla , Spain.
J Phys Chem Lett. 2018 Jul 19;9(14):3891-3896. doi: 10.1021/acs.jpclett.8b01830. Epub 2018 Jul 9.
Herein we present a combined study of the evolution of both the photoluminescence (PL) and the surface chemical structure of organic metal halide perovskites as the environmental oxygen pressure rises from ultrahigh vacuum up to a few thousandths of an atmosphere. Analyzing the changes occurring at the semiconductor surface upon photoexcitation under a controlled oxygen atmosphere in an X-ray photoelectron spectroscopy (XPS) chamber, we can rationalize the rich variety of photophysical phenomena observed and provide a plausible explanation for light-induced ion migration, one of the most conspicuous and debated concomitant effects detected during photoexcitation. We find direct evidence of the formation of a superficial layer of negatively charged oxygen species capable of repelling the halide anions away from the surface and toward the bulk. The reported PL transient dynamics, the partial recovery of the initial state when photoexcitation stops, and the eventual degradation after intense exposure times can thus be rationalized.
在此，我们展示了一项综合研究，该研究涉及有机金属卤化物钙钛矿的光致发光（PL）和表面化学结构随环境氧气压力从超高真空升至千分之几大气压的演变。通过在X射线光电子能谱（XPS）室中在受控氧气气氛下分析光激发时半导体表面发生的变化，我们可以解释所观察到的丰富多样的光物理现象，并为光诱导离子迁移提供合理的解释，光诱导离子迁移是光激发过程中检测到的最显著且备受争议的伴随效应之一。我们发现了形成带负电荷的氧物种表层的直接证据，该表层能够将卤化物阴离子从表面排斥到体相中。因此，所报道的PL瞬态动力学、光激发停止时初始状态的部分恢复以及长时间强烈曝光后的最终降解都可以得到合理的解释。
