Optimizing Conjugation of Polymer Hole Transport Materials via Cyclic Alkoxylation for Highly Efficient and Stable Perovskite Solar Cells

Abstract Hole transport materials (HTMs) play a crucial role in realizing efficient perovskite solar cells (PSCs), as they improve perovskite affinity and passivation, charge transport and extraction, and ultimately the performance of PSCs. In this study, manipulating the conjugation extension in poly(triaryl amine) (PTAA) derivatives by cyclic alkoxylation of side benzene groups with benzo[d][1,3]dioxole (PTAAO5) and dihydrobenzo[b][1,4]dioxine (PTAAO6) is focused on. PTAAO6 exhibits extended π‐conjugation within the side groups, leading to improved energy level alignment with perovskite and enhanced charge carrier transport compared to both PTAA and PTAAO5. This strong conjugation also promotes interactions between PTAAO6 and the perovskite, resulting in larger grain sizes with reduced defects within the perovskite layer. Therefore, PSCs incorporating PTAAO6 as the HTM achieve an outstanding power conversion efficiency of 25.19%, along with excellent operational stability, retaining 90.2% of the initial PCE after 1000 h under ISOS‐L‐3 testing conditions. These results underscore cyclic alkoxylation as a promising approach for tailoring polymer HTMs and provide crucial insights for designing high‐performance PSCs.