A Halogen-free and Universally Volatile Solid Additive Enables Binary Organic Solar Cells to Exceed 19% Efficiency

Additive processing is widely employed for regulating physical morphology to improve the performance of organic solar cells (OSCs). However, the dosage of commonly used solvent additives is problematic to control, leading to poor reproducibility of devices. Thus, this work innovatively introduces a low-cost and commercialized material, dibenzoylmethane (DBM), as a volatile solid additive in OSCs based on PM6:Y6. DBM is well mixed with polymer donor and non-fullerene acceptor, simultaneously facilitating the ordered molecular orientation and stacking of both the donor and acceptor, which leads to an improved double-fibril network, thereby prolonging exciton diffusion length and suppressing charge carrier recombination. Ultimately, a champion power conversion efficiency (PCE) of 18.7% is achieved for DBM-processed devices, which is the highest value reported in PM6:Y6-based binary OSCs, and also achieved excellent thermal stability (T-80 > 200 h, 85 degrees C) and storage stability (T-80 > 5000 h). Moreover, the effect of DBM also exhibits decent universality in diverse blend systems, such as PM6:BTP-eC9, PTQ10:m-TEH, D18:N3, and D18:L8-BO, and an impressive PCE of 19.4% is achieved. These findings demonstrate that DBM, as a low-cost, halogen-free solid additive with excellent universality, is promising for effectively improving device performances in future OSC applications.