Tuning Polymer Dipole Moment of Hole Transport Materials with a Glycol Ethyl Substituted Strategy for Inverted Perovskite Solar Cells

Abstract The dipole moment of hole transport materials (HTMs) plays a vital role in improving the photovoltaic performance of inverted perovskite solar cells (PSCs). However, manipulating dipole moments of polymer HTMs, which have great operational and bias stability, remains challenging. In this work, polymer HTMs with varying lengths of glycol side chains, PTAC‐DEG and PTAC‐TEG, are developed. Using a random‐walk model extended from polymer chain conformation, PTAC‐DEG (with shorter glycol side chains) achieves a higher cumulative dipole moment than PTAC‐TEG. This finding can be attributed to the fact that smaller dipole angles in PTAC‐DEG enable better dipole alignment, while larger dipole angles in PTAC‐TEG promote dipole aggregation that reduces the integrated dipole moment. Perovskite films on PTAC‐DEG show enhanced crystallinity and lower trap density due to improved interfacial charge transport, a stronger built‐in electric field, and a better affinity due to the higher polymer dipole. PTAC‐DEG devices achieve a PCE of 25.8%, which is among the highest for PSCs based on polymer HTMs, and the devices exhibit outstanding stability under ISOS‐L‐3 (t₉₅ = 1300 h) and ISOS‐D‐3 (t₉₅ = 1200 h) conditions. This study highlights dipole moment modulation as a promising strategy for designing efficient, stable polymer HTMs for perovskite solar cells.