Nonalloyed α-phase formamidinium lead triiodide solar cells through iodine intercalation

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…