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.