A simple-structured benzo[1,2-b:4,5-b’]dithiophene-based molecule as a third component enables organic solar cells with over 18.2% efficiency

Research has shown that ternary strategy is an effective tool for improving the performance of organic solar cells (OSCs) and simple-structured small molecules with low-cost and wide bandgap which broadens the scope of the choice in third components recently attracted the attention of researchers. Herein, a small molecule with benzo[1,2-b:4,5-b’]dithiophene (BDT) core named BR-C12 which mixed well with PM6 has been designed and synthesized. Incorporating BR-C12 as third component into PM6:Y6, BR-C12 exhibits a complementary absorption with PM6 and Y6, promoted exciton dissociation and charge collection, reduced bimolecular recombination, resulting in more ordered molecular packing. The PM6:Y6:BR-C12 (1:1.2:0.1, weight ratio) OSC shows an improved power conversion efficiency (PCE) of 17.02% in comparison to host binary devises (16.42%). In addition, by employing BR-C12 as third component into PM6:L8-BO, the ternary device based on PM6:L8-BO:BR-C12 also achieves significant enhancement in device photovoltaic performance with a PCE of 18.26%. In addition, BR-C12-added ternary devices exhibit improved stability than binary ones. This work presents a method for constructing high-performance ternary OSCs and enriches the abundance of materials for the third components. A simple-structured small molecule of BR-C12 is used as third component in the binary blends of PM6:Y6 and PM6:L8-BO to achieve efficient ternary solar cells with enhanced PCEs up to 17.02% and 18.26%, respectively. [Display omitted] •Simple-structured small molecule as cost-effective third component were studied for PM6:Y6 ternary OPV.•The small molecule has good compatibility with PM6 which improves blend morphology and enhances charge transport.•Third component-added ternary devices exhibit improved stability over binary ones.•The ternary OPV with blend of PM6:L8-BO:BR-C12 achieved a PCE of 18.26%.