Overcoming the Stability Issue for Hydrophobic Hole Transporting Layers Utilized in Tin‐Lead Perovskite and Tandem Solar Cells

Abstract The stability of all‐perovskite tandem solar cells is an important issue due to the acidic nature of the hole transport layer (HTL) utilized, poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) in tin‐lead perovskite. Incorporating hydrophobic HTL, such as poly[bis(4‐phenyl)(2,4,6‐trimethylphenyl)amine] (PTAA), for tin‐lead perovskite solar cells (TLPSCs) is often hindered by poor film coverage of the perovskite layer. Herein, a non‐annealing approach is introduced to fabricate high‐quality PTAA films, which enables the formation of a dense and uniform perovskite layer. It is found that SnF 2 incorporated into the perovskite precursor promotes the horizontal spreading of PTAA, facilitates the formation of dangling bonds between N and Sn, and enhances π – π interactions combined with SnF 2 ‐induced crosslinking. Utilizing this approach in TLPSC, a record power conversion efficiency (PCE) of 22.67% is achieved for PTAA‐based devices. Furthermore, when applying TLPSC to all perovskite tandem solar cells, the polymeric PTAA HTL enables a fully covered intermediate recombination layer, ultimately for the tandem device to achieve an efficiency of 28.14% with excellent operating stability, attaining 96% for 500 h at the maximum power point under simulated one‐sun illumination. This study highlights the low cost, universality, and environment‐friendly way of the non‐annealing approach and underscores significant improvements for PTAA‐based all‐perovskite tandem solar cells.