Achieving 16.68% efficiency ternary as-cast organic solar cells

State-of-the-art organic solar cells (OSCs) often require the use of high-boiling point additive or post-treatment such as temperature annealing and solvent vapor annealing to achieve the best efficiency. However, additives are not desirable in large-scale industrial printing process, while post-treatment also increases the production cost. In this article, we report highly efficient ternary OSCs based on PM6:BTP-ClBr1:BTP-2O-4Cl-C12 (weight ratio=1:1:0.2), with 16.68% power conversion efficiency (PCE) for as-cast device, relatively close to its annealed counterpart (17.19%). Apart from obvious energy tuning effect and complementary absorption spectra, the improved PCE of ternary device is mainly attributed to improved morphological properties including the more favorable materials miscibility, crystallinity, domain size and vertical phase separation, which endorse suppressed recombination. The result of this work provides understanding and guidance for high-performance as-cast OSCs through the ternary strategy.