Enhanced Exciton Dissociation and Charge Transport Through Fine Morphology Tuning for Efficient Ternary Photovoltaics

The performance of ternary organic photovoltaics (OPVs) is highly dependent on the nanoscale morphology of the active layer, which directly governs the synergistic processes of exciton dissociation and charge transport. In this work, using the PM6:D18:BTP-4F material system, we achieve fine morphological optimization through precise composition control (PM6:D18:BTP-4F = 0.8:0.2:1.4). The optimized blend exhibits enhanced π-π stacking, as evidenced by a reduced distance of ∼3.66 Å from grazing incidence wide-angle x-ray scattering (GIWAXS) analysis, improved face-on molecular orientation, and continuous phase-separated domain sizes. These structural advantages lead to significantly promoted exciton dissociation (with a dissociation time τ₂ = 8.03 ps from transient absorption spectroscopy) and enhanced charge extraction capability (charge extraction time 0.326 µs from TPC). Molecular dynamics (MD) simulations reveal the lowest interaction energy (-7.71 × 10³ kcal/mol) for this blend, indicative of superior thermodynamic stability and favorable formation of a bicontinuous charge transport network. As a result, the devices deliver an outstanding power conversion efficiency of 20.13% (20.01 ± 0.08) together with remarkable operational stability. This study provides a morphology-guided strategy and mechanistic insight for synchronously optimizing exciton and charge management in high-performance ternary OPVs.