Dissecting the relationship of lateral substituents in organic semiconductors with molecular packing motif, charge transfer integral, and thin film morphology is of paramount importance to enhancing the mobility of hole-transporting layers and photovoltaic performance of emerging perovskite solar cells (PSCs). In this work, two dimethyltriphenylamino-substituted dithieno[3,2-b:2′,3′-d]pyrroles are synthesized for the hole-transporting layer in triple-cation lead halide PSCs. X-ray crystallographic analysis of organic single crystals and theoretical modeling on the microscopic hole transport paths have disclosed that with respect to AZ1 possessing one n-propyl lateral substituent, the AZ2 hole transporter with 4-methoxyphenyl is characteristic of a closer intermolecular packing owing to a less short-axis slipped cofacial π-stacking configuration, and a larger averaged domain of molecule aggregates, which jointly contribute to a higher thin film hole mobility. The AZ2-based PSC exhibits an excellent power c...