Binary Additives Synergistically Modulate Crystallization for Enhanced HTL‐Free Sn–Pb Perovskite Solar Cells

ABSTRACT The architecture of hole‐transport‐layer (HTL)‐free Sn–Pb perovskite solar cells (PSCs) structure simplifies the layered structure and reduces the solution processing steps, thereby enhancing the manufacturing compatibility and scalability of tandem solar cells. Sn–Pb PSCs application in HTL‐free architectures is hindered by rapid crystallization, severe interfacial defects, and Sn 2 + oxidation. Here we report a synergistic binary additive strategy employing semicarbazide hydrochloride (SCH) and N‐fluorobenzenesulfonimide (NFSI) to simultaneously regulate crystallization kinetics, passivate defects, and stabilize Sn–Pb perovskites in HTL‐free devices. SCH serves as a primary crystallization regulator, while NFSI interacts with undercoordinated Sn 2 + /Pb 2 + through sulfonyl coordination and π–metal interactions, enabling delayed crystallization, improved crystal orientation, and suppressed Sn 2 + oxidation. The combined additives (SCH&NFSI) markedly reduce the roughness of buried perovskite surface, suppress nonradiative recombination, and enhance interfacial charge extraction. As a result, HTL‐free mixed Sn–Pb PSCs achieve a power conversion efficiency (PCE) of 22.73% with a high open‐circuit voltage ( V OC ) of 0.877 V, together with excellent storage stability retaining over 91% of the initial efficiency after 1500 h. This work demonstrates an effective molecular‐level strategy for overcoming the intrinsic limitations of HTL‐free Sn–Pb perovskites, offering a viable pathway toward simplified and stable photovoltaic architectures.