Dimerized small molecule donor enables efficient ternary organic solar cells

Ternary organic solar cells (OSCs) are the feasible and efficient strategy to achieve the high-performance OSCs. It is of great significance to develop a superior third component candidate for constructing efficient ternary OSCs. In this work, we intelligently designed and synthesized a dimerized small molecule donor by connecting two asymmetric small molecule donors with the vinyl group, which is named DSMD-βV. This innovative oligomeric molecule DSMD-βV not only exhibits the complementary absorption and the cascade energy level arrangement with PM6 and BTP-eC9, but also regulates the phase separation micromorphology based on PM6:BTP-eC9. Consequently, PM6:DSMD-βV:BTP-eC9 based ternary device exhibits the improved exciton dissociation, charge transport and decreased recombination, thus achieving a superior power conversion efficiency (PCE) of 18.26 %, surpassing PM6:BTP-eC9 based binary (17.63 %). This work indicates that the dimerized small molecule donor is able to become a promising third component candidate, which also opens up a unique idea for the construction of efficient ternary organic solar cells.