Inverted Perovskite Solar Cells with >85% Fill Factor via Sequential Interfacial Engineering

Even the most efficient inverted p–i–n architecture perovskite solar cells (PSCs) are still inferior to those with regular n–i–p architecture, which is mainly limited by interfacial loss. Herein, both wet and dry metal–halide perovskite films are regulated through organic molecules–assisted sequential interfacial engineering for high‐performance inverted PSCs. In specific, organic acetic acid treatment on the wet film potently regulates the nucleation and crystallization of perovskite films. Then, further loading 4‐(dimethylamino)benzoic acid on the dry perovskite film creates a passivating agent layer to suppress defect formation, leading to more phase‐pure and conductive perovskite films. Combined experimental and theoretical results illustrate that such sequential treatment is beneficial for decreasing surface trap states, non‐radiative recombination, and carrier transport loss. As a result, the target inverted PSC exhibits an unprecedented high fill factor (FF) of 85.31% together with a champion efficiency of 21.37%, which is greatly improved relative to the reference (FF of 79.60%, and efficiency of 19.40%). It should be noted that such a high FF is among the highest report and corresponding to 94.38% of the Shockley–Queisser limited FF (90.39%) of PSCs with a bandgap of 1.576 eV. In addition, the storage stability against moisture of target inverted PSCs is remarkably enhanced.