Copper oxide appears to be a promising candidate for a hole transport layer (HTL) in emerging perovskite solar cells. Reasons for this are its good optical and electrical properties, cost-effectiveness, and high stability. However, is this really the case? In this study, we demonstrate that copper oxide, synthesized by a spray-coating method, is unstable in contact with formamidinium lead triiodide (FAPI) perovskite, leading to its decomposition. Using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and ultraviolet–visible (UV–vis) spectrophotometry, we find that the entire copper oxide diffuses into and reacts with the FAPI film completely. The reaction products are an inactive yellow δ-FAPI phase, copper iodide (CuI), and an additional new phase of copper formate hydroxide (CH₂CuO₃) that has not been reported previously in the literature.

中文翻译：

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氧化铜空穴传输层 (HTL) 上沉积的甲脒碘化铅 (FAPI) 的不稳定性

氧化铜似乎是新兴钙钛矿太阳能电池中空穴传输层（HTL）的有前途的候选者。其原因在于其良好的光电性能、成本效益和高稳定性。然而，事实真的是这样吗？在这项研究中，我们证明了通过喷涂法合成的氧化铜与甲脒三碘化铅（FAPI）钙钛矿接触时不稳定，导致其分解。使用 X 射线衍射 (XRD)、X 射线光电子能谱 (XPS) 和紫外可见 (UV-vis) 分光光度法，我们发现整个氧化铜完全扩散到 FAPI 薄膜中并与其发生反应。反应产物是不活泼的黄色δ-FAPI 相、碘化铜(CuI) 和先前文献中未报道过的氢氧化甲酸铜(CH ₂ CuO ₃ )的附加新相。