Band engineering at the interface of all-inorganic CsPbI2Br solar cells

An all-inorganic CsPbI2Br perovskite with excellent phase stability and thermal stability has been considered to be a promising candidate for photovoltaic application. However, low efficiency and high moisture sensitivity hinder its advancement. In this work, we exploit 4-bromobenzylamine hydriodate post-treatment on CsPbI2Br thin films to assist the extraction of holes and to block the flow of electrons to the hole transport layer through band engineering at the CsPbI2Br bulk/surface. We found through depth profile analysis that a small amount of BrBeAI permeates into the CsPbI2Br bulk and mainly locates at the CsPbI2Br grain boundaries. This treatment leads to an improved short-circuit current of CsPbI2Br solar cells and an enhanced efficiency from 13.10% to 14.63%. In addition, the incorporation of the hydrophobic organic component into perovskite films effectively enhances the moisture resistance. This result proves that utilizing organic ammonium salt to improve the performance of the device through band alignment is an effective strategy for all-inorganic perovskite solar cell optimization.

具有优异相稳定性与热稳定性的全无机CsPbI₂Br钙钛矿（all-inorganic CsPbI₂Br perovskite），被视为光伏应用领域极具潜力的候选材料。然而，较低的光电转换效率与较高的湿敏性阻碍了其进一步发展。本研究采用4-溴苄胺氢碘酸盐（4-bromobenzylamine hydriodate）对CsPbI₂Br薄膜进行后处理，通过在CsPbI₂Br体相与表面实施能带工程（band engineering），辅助空穴提取并阻碍电子向空穴传输层（hole transport layer）的迁移。通过深度剖面分析（depth profile analysis）我们发现，少量该改性剂渗透进入CsPbI₂Br体相，且主要分布于CsPbI₂Br的晶界处。该后处理策略使CsPbI₂Br太阳能电池的短路电流（short-circuit current）得到显著提升，光电转换效率从13.10%提升至14.63%。此外，将疏水有机组分（hydrophobic organic component）引入钙钛矿薄膜后，材料的耐湿性能得到有效增强。本研究结果证实，通过有机铵盐（organic ammonium salt）调控能带对齐（band alignment）以提升器件性能，是优化全无机钙钛矿太阳能电池（all-inorganic perovskite solar cell）的有效策略。