Enhanced short circuit current density and efficiency of ternary organic solar cells by addition of a simple copolymer third component

Abstract Ternary strategy is one of the most effective methods for improving the power conversion efficiency (PCE) of organic solar cells (OSCs). The selection of the third component is very important for improving device performance. In this study, we demonstrated a simple and effective copolymer, PBDTDTzT, which is based on a benzo[1,2-b:4,5-b’]dithiophene donor unit and 2,5-di(thiazol-2-yl)thiophene acceptor unit, as the third component in the PM6:Y6 system. An optimal ternary device based on PM6:PBDTDTzT:Y6 (w/w = 1:0.1:1.1) achieved an impressive PCE of 17.0%. Detailed studies revealed that the loading of PBDTDTzT into the PM6:Y6 blend can not only optimize the ladder-type arrangement of energy levels but can also further optimize the morphology of the blend film, leading to balanced charge transport and reduced charge recombination simultaneously. Enhanced device performance is a result of the strong crystallization of PBDTDTzT and good compatibility between PBDTDTzT and PM6:Y6 blends. The results indicate that PBDTDTzT is a promising third component of high-efficiency ternary OSCs.