Duan Chenhui, Liang Zihui, Cao Jinguo, Jin Bowen, Ming Yidong, Wang Shimin, Ma Binghe, Ye Tao, Wu Congcong
Key Laboratory for the Green Preparation and Application of Functional Materials, Hubei Key Laboratory of Polymer Materials, School of Materials Science and Engineering, Hubei University, Wuhan 430062, China.
Ministry of Education Key Laboratory of Micro/Nano Systems for Aerospace, Northwestern Polytechnical University, Xi'an 710072, China.
ACS Appl Mater Interfaces. 2022 Sep 28;14(38):43298-43307. doi: 10.1021/acsami.2c11677. Epub 2022 Sep 13.
Formamidinium (FA)-based perovskites remained state-of-the-art in the field of perovskite solar cells (PSCs) owing to the exceptional absorption and carrier transport properties, while the transition from photoactive (α-) to photoinactive (δ-FAPbI) phase is the impediment that causes performance degradation and thus limits the deployment of FA-based PSCs. The unfavorable phase transition originates from tensile strain in the FAPbI crystal lattice, which undergoes structural reorganization for lattice strain balancing. In this work, we found that the ionic liquid (IL) could be used as the strain coordinator to balance the lattice strain for stability improvement of FAPbI perovskite. We theoretically studied the electronic coupling between IL and FAPbI and unraveled the originality of the IL-induced compressive strain. The strain-relaxed α-FAPbI by IL showed robust stability against environmental factors, which can withstand ambient aging for 40 days without any phase transition or decomposition. Moreover, the strain-relaxed perovskite films showed a lower trap density and resulted in conversion efficiency improvement from 18.27 to 19.88%. Based on this novel strain engineering strategy, the unencapsulated PSCs maintained 90% of their initial efficiency under ambient-air aging for 50 days.
基于甲脒（FA）的钙钛矿由于其优异的吸收和载流子传输特性，在钙钛矿太阳能电池（PSC）领域一直处于领先地位，而从光活性（α-）到光无活性（δ-FAPbI）相的转变是导致性能下降的障碍，从而限制了基于FA的PSC的应用。这种不利的相变源于FAPbI晶格中的拉伸应变，该晶格会进行结构重组以平衡晶格应变。在这项工作中，我们发现离子液体（IL）可以用作应变协调剂来平衡晶格应变，以提高FAPbI钙钛矿的稳定性。我们从理论上研究了IL与FAPbI之间的电子耦合，并揭示了IL诱导的压缩应变的起源。通过IL实现应变弛豫的α-FAPbI对环境因素表现出强大的稳定性，能够承受40天的环境老化而不发生任何相变或分解。此外，应变弛豫的钙钛矿薄膜显示出较低的陷阱密度，并使转换效率从18.27%提高到19.88%。基于这种新颖的应变工程策略，未封装的PSC在环境空气老化50天的情况下仍保持其初始效率的90%。
