Star‐Shaped Organic Semiconductor with Extraordinary Thermomechanical Property and Solution Processability for Stable Perovskite Solar Cells

Abstract Achieving the desired thermomechanical properties for highly solution‐processable organic semiconductors is challenging but crucial for heat tolerance of emerging optoelectronic devices. To this end, the successful synthesis of triphenylene–ethylenedioxythiophene‐dimethoxytriphenylamine (TP–ETPA), a star‐shaped organic semiconductor, is reported through a direct arylation reaction that involves ETPA, an electron donor, being grafted densely onto TP, which possesses six electron‐equivalent functionalization sites. Remarkably, TP–ETPA exhibits significantly improved hole mobility compared to 2,2′,7,7′‐tetrakis( N , N ‐di‐ p ‐methoxyphenyl‐amine)‐9,9′‐spirobifluorene (spiro‐OMeTAD) at a given hole density, owing to its lower energetic disorder, larger average centroid distance, and smaller reorganization energy. TP–ETPA, with a molecular weight of 2888 Da and lacking flexible chains, demonstrates extraordinary solubility in nonpolar solvents, enabling the formation of dense, pinhole‐free films through solution codeposition with an air‐doping promoter. By utilizing the p‐doped TP–ETPA composite as the hole transport layer, perovskite solar cells with an average power conversion efficiency of 23.4% are successfully fabricated. Notably, these devices display significantly enhanced operational stability and thermal stability at 85 °C. Molecular dynamics simulations reveal that the TP–ETPA‐based hole transport layer possesses a high cohesive energy density, resulting in a large elastic modulus and slow diffusion of external species.