Regulating Bifacial Surface Potential of Perovskite Film Enables Efficient Perovskite Solar Cells Universal for Different Charge Transport Layers

Abstract Planar perovskite solar cells (PSCs) show huge promise as an efficient photovoltaic technology, where the inefficient carrier transport at the hetero‐interface largely limits their performance advancement. Herein, bifacial surface potential regulation is realized in a monolithic perovskite film through interface doping, leading to optimized dual‐interfacial energy level alignment. In a n‐i‐p planar device, the up‐shift of Fermi level on the perovskite bottom surface is first achieved through bottom‐up diffusion of Li ⁺ . Then, vitamin D2 is incorporated into the methoxy‐Phenethylammonium iodide (MeO‐PEAI) passivator, which can neutralize the up‐shift of the Fermi level of perovskite top surface induced by MeO‐PEAI passivation and further induce its down‐shift. Both experimental measurements and theoretical simulation reveal that the bifacial surface potential regulation effectively promotes interfacial carrier transport and reduces carrier recombination, enhancing the adaptability of efficient PSCs to different charge transport materials. Impressively, the PSCs with 2,2′,7,7′‐Tetrakis [N, N‐di(4‐methoxyphenyl) amino]‐9,9′‐spirobifluorene (Spiro‐OMeTAD) and 2,4,6‐Trimethyl‐N, N‐diphenylaniline (PTAA) achieve efficiencies of 26.05% (certificated 25.80%) and 24.65%, respectively. Besides, the device can maintain 99% of its highest efficiency after aging more than 2200 h in ambient air with a relative humidity of ≈20%, showing excellent stability.