Molecular Doping Synergistic Effect Enables Efficient and Stable Wide-Bandgap Perovskite Solar Cells

In recent years, (4-(3,6-dimethyl-9<i>H</i>-carbazol-9-yl)butyl)phosphonic acid (Me-4PACz) has emerged as a promising interfacial material for wide-bandgap perovskite solar cells (WBG PSCs). However, it suffers from several inherent drawbacks, such as spontaneous aggregation, poor film wettability, low coverage, and weak anchoring to the substrate, which severely compromise interfacial contact between the perovskite and the hole transport layer (HTL), ultimately degrading device performance. In this work, we constructed a co-self-assembled monolayer (Co-SAM) HTL by incorporating pentafluorobenzylphosphonic acid (pFBPA) into Me-4PACz. This strategy not only effectively suppresses the self-aggregation of Me-4PACz but also significantly enhances the hole transport capability of the HTL. Additionally, the interaction between the phosphonic acid groups of pFBPA and PbI₂ in the perovskite precursor facilitates controlled nucleation of the perovskite film. Furthermore, the fluorine atoms confer excellent hydrophobicity on the buried perovskite interface. Ultimately, this approach yields a dense, pinhole-free buried perovskite interface along with enhanced crystallinity and moisture resistance of the perovskite layer. The optimized device achieves a power conversion efficiency (PCE) of 20.9% with a high open-circuit voltage (<i>V</i>_OC) of 1.36 V. Moreover, the encapsulated device retains 80% of its initial efficiency after 1920 h of storage under ambient conditions (60% relative humidity) and the device retains 80% of the initial PCE after 460 h of maximum power point tracking.