Defect Management and Ion Infiltration Barrier Enable High-Performance Perovskite Solar Cells

The stability of perovskite solar cells (PSCs) has been considered as one of the major obstacles toward practical application. Defects in the perovskite layer and ion infiltration from the hole transport layer (HTL) can trigger degradation of n-i-p PSCs. Herein, phenylhydrazine-4-sulfonic acid (PHPA) was employed as an additive to modulate perovskite crystallization during film formation, enlarging the perovskite crystal grain sizes to ∼3 μm. Density functional theory (DFT) calculations revealed that PHPA could effectively inhibit the formation of iodine vacancies (VI) and passivate the under-coordinated Pb2+ ions. Additionally, perfluorooctanoic acid (PFOA) was adopted to passivate the surface located dangling Pb2+ defects, improve the surface hydrophobicity, and inhibit Li+ ion migration from the HTL to the bottom perovskite, thus enhancing the device's environmental and operational stability. Consequently, the resulting devices delivered a champion efficiency of 25.1% with an excellent maximum-power-point (MPP) tracking stability.