20.2% Efficiency Organic Photovoltaics Employing a π-Extension Quinoxaline-Based Acceptor with Ordered Arrangement

Organic solar cells, as a cutting-edge sustainable renewable energy technology, possess a myriad of potential applications, while the bottleneck problem of less than 20% efficiency limits the further development. Simultaneously achieving an ordered molecular arrangement, appropriate crystalline domain size, and reduced nonradiative recombination poses a significant challenge and is pivotal for overcoming efficiency limitations. This study employs a dual strategy involving the development of a novel acceptor and ternary blending to address this challenge. A novel non-fullerene acceptor, SMA, characterized by a highly ordered arrangement and high lowest unoccupied molecular orbital energy level, is synthesized. By incorporating SMA as a guest acceptor in the PM6:BTP-eC9 system, it is observed that SMA staggered the liquid-solid transition of donor and acceptor, facilitating acceptor crystallization and ordering while maintaining a suitable domain size. Furthermore, SMA optimized the vertical morphology and reduced bimolecular recombination. As a result, the ternary device achieved a champion efficiency of 20.22%, accompanied by increased voltage, short-circuit current density, and fill factor. Notably, a stabilized efficiency of 18.42% is attained for flexible devices. This study underscores the significant potential of a synergistic approach integrating acceptor material innovation and ternary blending techniques for optimizing bulk heterojunction morphology and photovoltaic performance.