Halogen Radical‐Activated Perovskite‐Substrate Buried Heterointerface for Achieving Hole Transport Layer‐Free Tin‐Based Solar Cells with Efficiencies Surpassing 14%

Sn‐based perovskites have emerged as one of the most promising environmentally‐friendly photovoltaic materials. Nonetheless, the low‐cost production and stable operation of Sn‐based perovskite solar cells (PSCs) are still limited by the costly hole transport layer (HTL) and the under‐optimized interfacial carrier dynamics. Here, we innovatively developed a halogen radical chemical bridging strategy that enabled to remove the HTL and optimize the perovskite‐substrate heterointerface for constructing high‐performance, simplified Sn‐based PSCs. The modification of ITO electrode by highly active chlorine radicals could effectively mitigate the surface oxygen vacancies, alter the chemical constitutions, and favorably down‐shifted the work function of ITO surface to be close to the valence band of perovskites. As a result, the interfacial energy barrier was reduced by 0.20 eV and the carrier dynamics were optimized at the ITO/perovskite heterointerface. Encouragingly, the efficiency of HTL‐free Sn‐based PSCs was enhanced from 6.79% to 14.20%, representing the record performance for the Sn perovskite photovoltaics in the absence of HTL. Notably, the target device exhibited enhanced stability for 2000 h. The Cl‐RCB strategy is also versatile to construct Pb‐based and mixed Sn‐Pb HTL‐free PSCs, achieving efficiencies of 22.27% and 21.13%, respectively, all representing the advanced device performances for the carrier transport layer‐free PSCs.