Nonalloyed α-phase formamidinium lead triiodide solar cells through iodine intercalation
Yu Zhang, Yanrun Chen, Yanrun Chen, Guilin Liu, Yuetong Wu, Zhenyu Guo, Rundong Fan, Kailin Li, Huifen Liu, Yepin Zhao, Tim Kodalle, Yihua Chen, Yihua Chen, Cheng Zhu, Yang Bai, Qi Chen, Huanping Zhou
Abstract
Formamidinium lead triiodide (FAPbI 3 ) is considered the most promising composition for high-performing single-junction solar cells. However, nonalloyed α-FAPbI 3 is metastable with respect to the photoinactive δ-phase. We have developed a kinetic modulation strategy to fabricate high-quality and stable nonalloyed α-FAPbI 3 films, assisted by cogenetic volatile iodine intercalation and decalation. The intercalation of iodine facilitated the formation of corner-sharing Pb-I framework building blocks and reduced the kinetic barrier for α-FAPbI 3 formation, whereas the iodine decalation improved the final perovskite film quality in terms of composition purity and overall homogeneity. Solar cells based on this nonalloyed α-FAPbI 3 (free of other extrinsic composition ions) achieved a power conversion efficiency of >24%. The devices also exhibited excellent durability, retaining 99% of their original power conversion efficiency after operating for more than 1100 hours at 85° ± 5°C under illumination.