Department of Materials Science and Engineering, City University of Hong Kong, Kowloon, Hong Kong 999077, P. R. China.
Department of Chemistry, City University of Hong Kong, Kowloon, Hong Kong 999077, P. R. China.
J Am Chem Soc. 2023 Mar 15;145(10):5920-5929. doi: 10.1021/jacs.2c13566. Epub 2023 Mar 6.
Functional additives that can interact with the perovskite precursors to form the intermediate phase have been proven essential in obtaining uniform and stable α-FAPbI films. Among them, Cl-based volatile additives are the most prevalent in the literature. However, their exact role is still unclear, especially in inverted perovskite solar cells (PSCs). In this work, we have systematically studied the functions of Cl-based volatile additives and MA-based additives in formamidinium lead iodide (FAPbI)-based inverted PSCs. Using in situ photoluminescence, we provide clear evidence to unravel the different roles of volatile additives (NHCl, FACl, and MACl) and MA-based additives (MACl, MABr, and MAI) in the nucleation, crystallization, and phase transition of FAPbI. Three different kinds of crystallization routes are proposed based on the above additives. The non-MA volatile additives (NHCl and FACl) were found to promote crystallization and lower the phase-transition temperatures. The MA-based additives could quickly induce MA-rich nuclei to form pure α-phase FAPbI and dramatically reduce phase-transition temperatures. Furthermore, volatile MACl provides a unique effect on promoting the growth of secondary crystallization during annealing. The optimized solar cells with MACl can achieve an efficiency of 23.1%, which is the highest in inverted FAPbI-based PSCs.
在获得均匀稳定的α-FAPbI 薄膜方面，能够与钙钛矿前驱体相互作用形成中间相的功能添加剂已被证明是必不可少的。其中，基于 Cl 的挥发性添加剂在文献中最为常见。然而，它们的确切作用仍不清楚，特别是在倒置钙钛矿太阳能电池（PSC）中。在这项工作中，我们系统地研究了基于 Cl 的挥发性添加剂和基于 MA 的添加剂在甲脒碘化铅（FAPbI）基倒置 PSC 中的作用。通过原位光致发光，我们提供了明确的证据来揭示挥发性添加剂（NHCl、FACl 和 MACl）和基于 MA 的添加剂（MACl、MABr 和 MAI）在 FAPbI 的成核、结晶和相变过程中的不同作用。基于以上添加剂，提出了三种不同的结晶途径。发现非 MA 挥发性添加剂（NHCl 和 FACl）可促进结晶并降低相变温度。基于 MA 的添加剂可以快速诱导富含 MA 的核形成纯α相 FAPbI，并显著降低相变温度。此外，挥发性 MACl 在退火过程中对促进二次结晶的生长具有独特的作用。使用 MACl 的优化太阳能电池可实现 23.1%的效率，这是倒置 FAPbI 基 PSC 中的最高效率。
