Cascade Reaction in Organic Hole Transport Layer Enables Efficient Perovskite Solar Cells

Abstract The doped organic hole transport layer (HTL) is crucial for achieving high‐efficiency perovskite solar cells (PSCs). However, the traditional doping strategy undergoes a time‐consuming and environment‐dependent oxidation process, which hinders the technology upgrades and commercialization of PSCs. Here, we reported a new strategy by introducing a cascade reaction in traditional doped Spiro‐OMeTAD, which can simultaneously achieve rapid oxidation and overcome the erosion of perovskite by 4‐tert‐butylpyridine (tBP) in organic HTL. The ideal dopant iodobenzene diacetate was utilized as the initiator that can react with Spiro to generate Spiro⋅ + radicals quickly and efficiently without the participation of ambient air, with the byproduct of iodobenzene (DB). Then, the DB can coordinate with tBP through a halogen bond to form a tBP‐DB complex, minimizing the sustained erosion from tBP to perovskite. Based on the above cascade reaction, the resulting Spiro‐based PSCs have a champion PCE of 25.76 % (certificated of 25.38 %). This new oxidation process of HTL is less environment‐dependent and produces PSCs with higher reproducibility. Moreover, the PTAA‐based PSCs obtain a PCE of 23.76 %, demonstrating the excellent applicability of this doping strategy on organic HTL.