Lu Yue, Si Zhixiang, Liu Hongpeng, Ge Yang, Hu Jingcong, Zhang Zeyu, Mu Xulin, Selvakumar Karuppaiah, Sui Manling
Beijing Key Laboratory of Microstructure and Properties of Solids, Institute of Microstructure and Properties of Advanced Materials, Faculty of Materials and Manufacturing, Beijing University of Technology, Beijing, 100124, P. R. China.
Chemistry. 2021 Feb 19;27(11):3729-3736. doi: 10.1002/chem.202003121. Epub 2021 Jan 14.
Theoretical studies have shown that surface terminations, such as MAI or PbI layers, greatly affect the environmental stability of organic-inorganic perovskite. However, until now, there has been little effort to experimentally detect the existence of MAI or PbI terminations on MAPbI grains, let alone disclose their effects on the humidity degradation pathway of perovskite solar cell. Here, we successfully modified and detected the surface terminations of MAI and PbI species on polycrystalline MAPbI films. MAI-terminated perovskite film followed the moisture degradation process from MAPbI to hydrate MAPbI ⋅H O and then into PbI , with penetration of water molecules being the main driving force leading to the degradation of MAPbI layer by layer. In contrast, for the PbI-terminated perovskite film in a humid atmosphere, a deprotonation degradation pathway was confirmed, in which the film preferentially degraded directly from MAPbI into PbI , here the iodine defects played a key role in promoting the dissociation of water molecules into OH and further catalyzing the decomposition of perovskite.
理论研究表明，表面终止层，如MAI或PbI层，会极大地影响有机-无机钙钛矿的环境稳定性。然而，到目前为止，几乎没有努力通过实验检测MAPbI晶粒上MAI或PbI终止层的存在，更不用说揭示它们对钙钛矿太阳能电池湿度降解途径的影响了。在此，我们成功地修饰并检测了多晶MAPbI薄膜上MAI和PbI物种的表面终止层。MAI终止的钙钛矿薄膜遵循从MAPbI到水合物MAPbI·H₂O再到PbI₂的水分降解过程，水分子的渗透是导致MAPbI层逐层降解的主要驱动力。相比之下，对于在潮湿气氛中PbI终止的钙钛矿薄膜，证实了一种去质子化降解途径，其中薄膜优先直接从MAPbI降解为PbI₂，这里碘缺陷在促进水分子离解为OH⁻并进一步催化钙钛矿分解中起关键作用。
