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 × 1014 Jones at 805 nm (specific detectivity: 4.26 × 1013 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 cm2). 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.