Block copolymer compatibilizer for efficient and stable nonfullerene organic solar cells

High-efficiency nonfullerene organic solar cells with long-term stability is crucial for future commercialization in the field of organic photovoltaics. Herein, we designed and synthesized a block copolymer, namely PM6-b-PTY6, containing both donor PM6 and Y6 segments in the polymer backbone. We then first demonstrated that the use of such block copolymer as a compatibilizer in high-efficiency PM6:Y6 based benchmark nonfullerene solar cells, simultaneously enhancing their power conversion efficiency and long-term stability. Detailed experimental results reveal that the addition of PM6-b-PTY6 into PM6:Y6 blend can effectively optimize carrier dynamic process, enhance donor–acceptor miscibility, and stabilize the blend morphology. Additionally, this strategy shows similar function when applied to other system like D18-Cl:Y6. As a result, enhanced efficiencies of 16.48% and 17.55% for PM6:Y6 and D18-Cl:Y6 solar cell are achieved, respectively. More importantly, the inverted PM6:Y6 devices exhibit improved stability, retaining 0.81 and 0.86 of the initial efficiency after 550 h aging under ambient and thermal stress, respectively. These results indicate that the compatible block copolymer could provide a fresh strategy to design more efficient nonfullerene organic solar cells.