Dark electrical bias effects on moisture-induced degradation in inverted lead halide perovskite solar cells measured by using advanced chemical probes
Dark electrical bias effects on moisture-induced degradation in inverted lead halide perovskite solar cells measured by using advanced chemical probes
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DOI：
10.1039/c7se00545h
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发表时间：
2018-04-01
影响因子：
5.6
通讯作者：
Tsoi, Wing C.
中科院分区：
文献类型：
--
作者：
Barbe, Jeremy;Kumar, Vikas;Tsoi, Wing C.
新兴的卤化铅钙钛矿材料在一系列光电器件中具有巨大的应用潜力，例如太阳能电池、发光二极管、晶体管和激光器。然而，这些技术的大规模商业化将取决于活性材料在环境和操作条件下稳定的能力。在这项工作中，我们首次测量了在不同环境中的黑暗中的电偏压诱导的倒置钙钛矿太阳能电池的降解，并得出结论，湿度与电偏压耦合导致CH3NH3PbI3快速降解为PbI2。显微拉曼和光致发光显示，由于水分进入，降解从电池的边缘开始。通过使用新的局部拉曼瞬态光电流测量，我们能够探测在退化区域和非退化区域中的局部离子迁移，并发现PbI2的形成可以通过减少离子迁移来钝化钙钛矿。二次电子高光谱成像技术是一种先进的扫描电子显微镜技术，可以从横截面探测单个晶粒的组成，显示不同晶粒的降解远非均匀。通过电位阶跃计时电流法，我们还发现偏压退化与移动的离子密度密切相关。已建立的方法与几种新型分析工具的独特结合，提供了从纳米尺度到电池水平的倒置钙钛矿太阳能电池的偏压降解起源的见解，并展示了这些新工具用于研究其他钙钛矿系统中降解的潜力。
Emerging lead halide perovskite materials have enormous potential for application in a range of optoelectronic devices, such as solar cells, light emitting diodes, transistors and lasers. However, the large-scale commercialization of these technologies will depend on the ability of the active material to be stable under environmental and operating conditions. In this work, we measured for the first time the electrical bias-induced degradation of inverted perovskite solar cells in the dark in different environments and concluded that humidity coupled with electrical bias results in fast degradation of CH3NH3PbI3 into PbI2. Micro-Raman and photoluminescence show that the degradation starts from the edge of the cell due to moisture ingress. By using novel local Raman-transient photocurrent measurements, we were able to probe local ion migration in the degraded region and non-degraded region and found that the formation of PbI2 can passivate the perovskite by reducing ion migration. The degradation is far from uniform across different grains as revealed by secondary electron hyperspectral imaging, an advanced scanning electron microscopy technique which allows probing the composition of individual grains from the cross section. By using potential step chronoamperometry, we also found that the bias degradation is closely related to the density of mobile ions. The unique combination of established methods with several novel analytical tools provides an insight into the origin of the bias-degradation of inverted perovskite solar cells from the nano-scale to the cell level, and demonstrates the potential of these novel tools for studying the degradation in other perovskite systems.