Functional Group Transposition Enables Antiparallel–Parallel Packing Switching in Dithieno[3,2‐b:2′,3′‐d]pyrrole Self‐Assembled Molecules for Efficient Organic Photovoltaics

Concurrently regulating interfacial and bulk charge dynamics, which requires simultaneous control over indium‐tin‐oxide (ITO) interfacial properties and active layer morphology, is critical for advancing and integrating organic solar cells (OSCs) and photodetectors (OPDs). However, designing universal hole‐transport‐layers (HTLs) compatible with diverse photovoltaic platforms remains a fundamental challenge. We propose two regioisomeric acceptor–donor–acceptor type self‐assembled molecules (SAMs) with dithienopyrrole (DTP) core. Simply swapping ortho‐/para‐ positions of trifluoromethyl and chlorine on the phenyl termini switches molecular stacking from disordered antiparallel to well‐ordered parallel. This programmable assembly benefits to yield uniform HTLs on ITO with homogeneous surface potential, alongside enhanced crystallinity and vertical phase segregation in the PM6:Y6 active layer. Optimized OSCs and OPDs achieve 18.70% power conversion efficiency (PCE) and a shot‐noise‐limited specific detectivity of 6.52 × 10 14 Jones at 805 nm (specific detectivity: 4.26 × 10 13 Jones). The versatility of the optimized SAM is validated across state‐of‐the‐art binary/ternary systems (PCE of 20.92% for D18:L8‐BO:BTP‐eC9 system), even upon scaling up (PCE of 19.1% for PM6:L8‐BO:BTP‐eC9 system, device area = 0.6 cm 2 ). This work not only elevates DTP as a competitive alternative against carbazole for SAMs, but also establishes functional group transposition as a finely tuned molecular lever that co‐engineers interfacial order and active‐layer morphology toward high‐performance organic optoelectronics.