Performance Optimization of Perovskite Solar Cells via Fluorinated Carbonyl Additives

Perovskite solar cells (PSCs) have emerged as a promising photovoltaic technology due to their long carrier diffusion lengths, tunable bandgaps, and high light absorption coefficients. However, instability remains a significant barrier to their commercialization. In this study, we introduce two carbonyl small molecule additives with varying fluorine atom counts: 4,5-difluoro-phthalic anhydride (2FPA) and tetrafluorophthalic anhydride (4FPA). The fluorine atoms and carbonyl groups interact to passivate defects in the perovskite structure. The strong interaction between 4FPA and the perovskite facilitates slow crystal growth and effective defect passivation, significantly suppressing nonradiative recombination and enhancing carrier transport efficiency. Consequently, the power conversion efficiency (PCE) of PSCs incorporating 4FPA has improved from 21.49 to 23.21%. Additionally, the fluorine atoms in the additive interact with FA⁺ in the perovskite to form strong hydrogen bonds and coordinate bonds with Pb²⁺, thereby enhancing device stability. In unencapsulated conditions, after approximately 1000 h in ambient air with 50 to 60% humidity, the 4FPA device retains 87% of its initial efficiency.