The unprecedented speed at which the performance of solar cells based on solution‐processed perovskite thin films has increased, in some ways, appears to violate conventional understanding of device optimization. The relatively poor coverage of the TiO₂ electron transport layer by the absorber should cause shunting of the cell. This, however, is not the case. In this paper, it is attempted to explain this “discrepancy.” Insights into coverage, morphology, local elemental composition, and spatially resolved electronic structure of CH₃NH₃PbI_(3−x)Cl_x perovskite absorbers wet‐chemically deposited on planar compact TiO₂ electron transport material (ETM) are revealed. Microscopy images indicate an incomplete coverage of the ETM. Depending on the degree of coverage, a variation in iodine oxidation and metallic lead formation is found. With the electronic structure of the absorber and the ETM established experimentally and taking literature on the commonly used hole transport material spiro‐MeOTAD into account, it is revealed that excellent charge selectivity occurs at the interfaces between the absorber and both the hole and electron transport layers. It can also be surmised that, crucially, any direct interface between the TiO₂ and spiro‐MeOTAD would be characterized by a large recombination barrier preventing shunts; to some extent minimizing the negative effects of absorber pinholes.

中文翻译：

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对溶液加工钙钛矿化学和电子结构的空间分辨洞察力—为什么（不）担心针孔

基于固溶钙钛矿薄膜的太阳能电池性能以前所未有的速度提高，在某些方面似乎违反了对器件优化的传统理解。吸收剂对TiO ₂电子传输层的相对较差的覆盖应导致电池分流。但是，事实并非如此。本文试图解释这种“差异”。对湿法化学沉积在平面致密TiO ₂上的CH ₃ NH ₃ PbI _{（3- x）} Cl _x钙钛矿吸收剂的覆盖范围，形态，局部元素组成和空间分辨的电子结构的见解揭示了电子传输材料（ETM）。显微镜图像表明ETM的覆盖范围不完整。根据覆盖程度，发现碘氧化和金属铅形成的变化。通过实验建立吸收体和ETM的电子结构，并考虑到常用的空穴传输材料spiro-MeOTAD的文献，可以发现，在吸收体与空穴和电子传输层之间的界面处都具有出色的电荷选择性。还可以推测，至关重要的是，TiO ₂和spiro-MeOTAD之间的任何直接界面都将具有防止分流的大型复合势垒。在某种程度上最大程度地减少了吸收器针孔的负面影响。