Hydroxyl‐Rich d‐Sorbitol to Address Transport Layer/Perovskite Interfacial Issues toward Highly Efficient and Stable 2D/3D Tin‐Based Perovskite Solar Cells

Abstract 2D/3D mixed tin (Sn)‐based perovskites serving as excellent active layers possess a potential for enhancing film/device stabilities, open‐circuit voltage, and power conversion efficiency (PCE) of perovskite solar cells (PSCs). Unfortunately, the poor morphology and low film coverage of these 2D/3D perovskites jeopardize their device performance and stability. Herein, doping of hydroxyl‐rich d‐sorbitol into hole transport layer poly(3,4‐ethenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) can effectively address the PEDOT:PSS/perovskite interfacial issues. The multihydroxyl groups from d‐sorbitol can sufficiently anchor iodide ions ([SnI₆]⁴⁻ or free I⁻) of PEA_0.1(FA_0.75MA_0.25)_0.9SnI₃ perovskite via hydrogen bond, which not only introduces more nucleation sites with improved crystallinity along the preferential crystal orientations, but also reduces the trap states’ density and suppresses the iodide ions’ migration. In the meanwhile, the content of SnI₂ is reduced in the resulting perovskite films. All of these are conducive to form compact and smooth high‐quality perovskite films with less traps and enhanced stability. Benefitting from these, an inverted PSC with a champion PCE of 10.46% and a lifetime of 700 h (25% attenuation in N₂) is eventually achieved. This work provides a promising approach to manufacture highly efficient and stable Sn‐based PSCs based on 2D/3D mixed perovskites.