All‐in‐One Molecule Regulated Buried Interface and Crystallization of Tin–Lead Perovskite for Efficient All‐Perovskite Tandem Solar Cells

Mixed tin-lead (Sn-Pb) perovskite solar cells (PSCs) are critical for advancing all-perovskite tandem solar technologies, as they resolve the efficiency limitations of single-junction devices. However, the widely used hole transport layer (HTL) poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) restricts performance and durability due to its acidic nature and moisture absorption. Additionally, the rapid crystallization of Sn-containing perovskites hinders the fabrication of uniform, high-quality mixed SnPb perovskite films. To address these challenges, this study incorporates 4-sulfophthalic acid triammonium salt (SATS) as a multifunctional additive into both the PEDOT:PSS layer and perovskite precursor solution. SATS modifies the physicochemical properties of PEDOT:PSS and slows perovskite crystallization, promoting films with enhanced crystallinity. Through these synergistic effects, the optimized single-junction SnPb PSCs achieve a power conversion efficiency (PCE) of 23.85%. Integrating these devices into two-terminal all-perovskite tandem architectures further delivers a remarkable efficiency of 28.74%.