Single-Crystal Seeds Inducing the Crystallization of High-Performance -FAPbI_3 for Efficient Perovskite Solar Cells

摘要

-phase formamidine lead iodine ( -FAPbI_3) as a competitive candidate topursue high-performance perovskite solar cells (PSCs) suffers from theweakness of random nucleation and disordered growth in chasing high-gradepolycrystalline films. Here, single-crystal seeds crystallization (SCSC) methodis proposed to obtain high-quality -FAPbI_3 perovskite films for the first time.Six single-crystals seeds (CsPbBr_3, CsPbI_3, FAPbBr_3, FAPbI_3, MAPbBr_3, andMAPbI_3) are employed to regulate -FAPbI_3 perovskite crystallization. Theseseeds act as nucleation sites and allow the perovskite to grow directly. Therapid crystallization significantly improves the crystallinity of perovskite filmswith uniform morphology, large grain size, and less defects. Of particularnote, FAPbBr_3 seed prefers to grow -FAPbI_3 epitaxially from FAPbBr_3@PbI_2heterostructure through a halogen anion exchange process. The average grainsize of FAPbBr_3-perovskite film is boosted to 2.6 μm, and the trap densityreduced by 11 times. The resultant FAPbBr_3-PSCs achieve a maximum powerconversion efficiency (PCE) of 23.84 with a high open-circuit voltage of1.18 V. The unencapsulated PSC retains 91 of the initial PCE after 3000 h ofstorage at ≈30-50 relative humidity and preserves 98.5 of the originalvalue after 155 h illumination with maximum power point tracking.