Green-Solvent Processable Polymeric Hole Transport Materials with Functional Groups for Inverted Perovskite Solar Cell

Exploring novel hole transporting materials (HTMs) with high hole mobility and eco-friendly processability are imperative for the commercialization of perovskite solar cells (PSCs). However, there is a "trade-off" that the introduction of large-conjugated units aiming to ensure high hole mobility, inevitably compromises the green-solvent solubility of HTMs. In this work, a hybrid strategy of rigidity and flexibility is proposed, in which the conjugated unit is assembled by the rigid binaphthylamine core, and the amide-bond constitutes the flexible backbone. Polar solubilizing units ethylenedioxythiophene and thiophene are used as bridges to construct two kinds of polymers, cited as EDOT-SMe and T-SMe, respectively. Both polymers achieve high hole mobility, well-matched energy levels and efficient defect passivation effect toward the perovskite films. When processing the HTM films with the green solvent (2-methylanisole), the corresponding PSCs deliver fill factors as high as 82.7% for EDOT-SMe and 81.9% for T-SMe, respectively. Consequently, PCEs of 20.25% for EDOT-SMe and 20.09% for T-SMe are realized, outperforming that of commercial polymer poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA, 19.71%). Moreover, PSCs with these polyamides achieve good long-term stability. This work paves a new path for exploring efficient and green-solvent processable polymeric HTMs.