Constructing High‐Performance Ternary Device Using Analogous Polymer Donors

Abstract

Both ternary copolymerization and ternary blending are effective methods to fine‐tune polymer structure and manipulate thin‐film morphology to improve device performance. In this work, three D‐A‐A‐A (D: donor, A: acceptor) terpolymer donors (FY1, FY2, and FY3) are synthesized by introducing BDD (1,3‐bis(2‐ethylhexyl)‐5,7‐di(thiophen‐2‐yl)benzo[1,2‐c:4,5‐c']dithiophene‐4,8‐dione) units into the D–A alternating copolymer PM6 backbone. Owing to the promoted conjugated planarity and excellent absorption of BDD, the obtained terpolymers display an extended absorption range and enhanced π–π stacking orientation, which is a promising third component in ternary device. As a result, the optimal FY1:PM6:BTP‐eC9‐based ternary device afforded an impressive power conversion efficiency (PCE) as high as 18.52%, owing to the efficient charge transport, negligible energy loss, and suitable domain size. The result provides an efficient method to obtain high‐performance polymer solar cells by using analogous polymer donors in ternary device.