Synergistic Regulation of Crystallization Kinetics and Thermodynamics by Liquid Crystal Engineering Enables Efficient and Stable Organic Solar Cells

Abstract

ABSTRACT Organic solar cells (OSCs) hold great promise for next‐generation photovoltaics, yet achieving both high efficiency and long‐term stability remains a formidable challenge. This difficulty originates from the multiple influences of crystallization kinetics and thermodynamics in bulk heterojunction films. Herein, we introduce a nematic liquid crystal, 3UTPP4, to synergistically regulate both the kinetic and thermodynamic aspects of film formation in the PM6:BTP‐eC9 system. 3UTPP4 prolongs the film formation process, enabling more controlled molecular assembly and effectively circumventing the metastable state (cold crystallization) of BTP‐eC9. The resulting films exhibit enhanced molecular ordering with reduced π–π stacking distance, suppressed recombination, and improved charge carrier mobility. Consequently, the optimized devices deliver a power conversion efficiency (PCE) of 20.07% with an excellent fill factor (FF) of 80.51%. Moreover, outstanding device stability was successfully realized, retaining 95% of the initial PCE after 1,600 h of storage in nitrogen and achieving a photothermal stability T80 exceeding 1,000 h. The generality of this strategy is further validated across other high‐performance systems, with D18:L8‐BO achieving an excellent PCE of 20.73% and an FF of 82.14%. This work establishes liquid crystal‐assisted synergistic regulation of kinetic and thermodynamic processes as a promising pathway toward efficient and stable OSCs.