• • Ternary all-PSC with PM6:PBDTF-DTP:PYIT achieves a power conversion efficiency of 18.01%, a 16.1% relative improvement over the binary PM6:PYIT baseline (15.51%), demonstrating the efficacy of the guest donor strategy.
• • The large dipole moment of the DTP-2T unit increases the dielectric constant of the active layer, which suppresses non-radiative energy loss and contributes to a higher open-circuit voltage (V_OC) in the ternary device.
• • PBDTF-DTP exhibits a higher molecular electrostatic potential than the host donor, enabling fine-tuning of donor-acceptor compatibility and promoting a nanoscale fibrillar network morphology that enhances charge generation and transport while suppressing recombination.
• • The guest polymer donor PBDTF-DTP deepens the highest occupied molecular orbital (HOMO) level, which is beneficial for increasing V_OC without compromising J_SC, as evidenced by the simultaneous enhancement of both parameters in the ternary device.