Synergistic Energetics and Exciton Management Driven by Interfacial Dipoles Enable 20.1% Efficient Organic Solar Cells.

Poly(3,4ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS, PP) is widely employed as a hole-transport layer in organic solar cells due to its optical transparency and solution-processability. However, PP application is often hindered by non-radiative recombination arising from interfacial energy-level misalignment, charge trapping, and suboptimal compatibility with the active layer. Herein, we propose an interfacial engineering strategy based on a donor-acceptor molecule with a rigid planar acceptor core and diphenylamine-based electron-donating peripheries, which facilitates intramolecular charge transfer. This intrinsic electronic asymmetry establishes an interface dipole layer upon the PP surface, effectively modulating the energy-level alignment to promote hole extraction and superior electron blocking. Simultaneously, the dipole layer optimizes the interfacial surface energy, thereby promoting molecular ordering in the active layer and nanoscale morphology. Furthermore, the dipole layer modulates exciton dynamics and suppresses non-radiative losses, leading to a champion power conversion efficiency (PCE) of 20.1% (compared to 18.5% for the control device) in a bulk-heterojunction device. The PCE of 19.9% in the quasi-bilayer structure also confirms the role of the interface dipole effect. This work establishes that the engineered interface dipole serves as an effective approach that unifies interfacial energetics and exciton management, offering a new strategy for high-performance, stable organic photovoltaics.