A Synergistic Hybrid Hole Transport Material for Efficient and Stable Tin–Lead Narrow Bandgap Perovskite Solar Cells

ABSTRACT Poly(3,4‐ethyleneldioxythiophene)‐poly(styrenesulfonate) (PEDOT:PSS) and poly[bis(4‐phenyl) (2,4,6‐trimethylphenyl)amine] (PTAA) are two common hole transport materials (HTMs) widely used in inverted perovskite solar cells (PSCs). However, they suffer from limitations: PEDOT:PSS exhibits inherent acidity and hydrophilicity, while PTAA shows low conductivity and hydrophobicity. To address this, we introduced PEDOT:PSS into the PTAA precursor solution. Owing to the self‐assembly behavior of the hybrid polymer in the solvent, some conductive PEDOT molecular chains liberated from the PEDOT:PSS macromolecular chains. These liberated conductive PEDOT molecules subsequently bind to PTAA via N–S bonds, forming a novel PTAA:PEDOT (P‐PTAA) polymer. The hybrid HTL leverages the conductive PEDOT:PSS and the newly formed P‐PTAA molecular chains to bridge hydrophobic PTAA domains, thereby establishing a continuous charge transport pathway. Consequently, both conductivity and wettability of the PTAA‐based hole transport layer (HTL) are enhanced. This optimization simultaneously improves perovskite crystal quality and facilitates charge transfer between the HTL and perovskite layer, resulting in significantly improved photoelectric conversion efficiency and stability of Sn–Pb NBG PSCs. Ultimately, we achieved an efficiency of 21.12% in inverted Sn–Pb NBG PSCs. Furthermore, a four‐terminal (4‐T) all‐perovskite tandem solar cell (APTSC), constructed by coupling this device with a semi‐transparent wide‐bandgap (WBG) PSC, exhibited efficiencies exceeding 24%. Remarkably, the 4‐T tandem device retained its initial PCE without degradation after 1200 h of storage, demonstrating exceptional stability for 4‐T APTSCs.