Three Birds with One Stone: Triple Defect Passivation of Tris(2,2,2-trifluoroethyl) Phosphate Enables 25.69% Efficient Inverted Perovskite Solar Cells.

Defect passivation is widely acknowledged as a crucial strategy for enhancing the efficiency and stability of perovskite solar cells (PSCs). However, it remains a formidable challenge to effectively address multiple defects simultaneously on both the top and bottom surfaces of perovskite films, as well as within the bulk, through a facile method. To tackle this dilemma, we have devised a triple passivation strategy, aiming to achieve a holistic passivation of defects at the aforementioned locations using a singular passivator. Specifically, a multifunctional molecule, tris(2,2,2-trifluoroethyl) phosphate (TTFP), is meticulously engineered as an additive in the antisolvent. This approach capitalizes a top-down gradient distribution of TTFP along the perovskite film, thereby enabling to mitigate the interfacial and bulk defects. Meanwhile, the unique molecular structure of TTFP facilitates simultaneous interactions with both cationic and anionic defects. Additionally, TTFP exerts a pronounced influence on the crystallization kinetics, thereby promoting the formation of highly crystalline perovskite films with substantially enlarged grain sizes. Consequently, the TTFP-based devices exhibit a champion power conversion efficiency (PCE) of 25.69%, accompanied by a notable improvement in stability. This work represents the successful implementation of comprehensive defect passivation, marking a significant instance in the advancement of efficient and stable PSC technology.