Balancing carrier mobility with solvent-solid hybrid additives for high-performance non-fullerene organic solar cells

Achieving balanced electron-hole mobility remains a critical challenge in boosting the photovoltaic performance of organic solar cells, as imbalanced mobilities lead to increased carrier recombination, reduced fill factor, and lower short-circuit current density. Herein, we propose a solid-solvent hybrid additive strategy to optimize the donor/acceptor vertical distribution and π-π stacking in the PM6:Y6 active layer. 1-Chloronaphthalene was employed as the solvent additive, while 2,5-dibromo-3,4-thiophenedinitrile, a molecule with a large dipole moment, served as the solid additive. The synergistic effect of 1-chloronaphthalene and 2,5-dibromo-3,4-thiophenedinitrile induced more ordered molecular stacking and enhanced charge transport pathways, which led to significantly improved and balanced carrier mobilities. Specifically, the electron mobility increased from 4.08 × 10⁻⁴ cm² V⁻¹ s⁻¹ to 1.17 × 10⁻³ cm² V⁻¹ s⁻¹, and the hole/electron mobility ratio (μ_h/μ_e) decreased from 1.62 to 1.15. These improvements facilitated more efficient exciton separation and suppressed charge recombination. Consequently, the OSCs exhibited simultaneous improvements in short-circuit current density, fill factor, and power conversion efficiency, with the PCE increasing from 16.35 % to 17.93 %. This study highlights the potential of solid-solvent hybrid additive strategies for balancing charge carrier mobilities and advancing OSC performance