In this study, a pyrazine-based acceptor is fused with two known donors benzodithiophene (BDT) and dithienobenzodithiophene (DTBDT) to synthesize a new D-A type polymer donor (NBDT-Pzt). New polymer NBDT-Pzt was synthesized and carried out the characterizations systematically. NBDT-Pzt showed film absorption peak at 540 nm and optical band gap of 1.96 eV. The complementary absorption and energy offsets were observed between NBDT-Pzt, PM6 polymer donors and L8-BO acceptor. Therefore, the insertion of pyrazine moiety downshifted the energy levels and enhanced coplanarity with optimized binary blend of PM6 and L8-BO. The PM6: NBDT-Pzt: L8-BO based ternary PSCs resulted an open-circuit voltage of 0.87 V, a short-circuit current density of 28.7 mA cm−2, and a fill factor of 74.0 %, corresponding to a power conversion efficiency (PCE) of 18.4 %. The results emphasize that NBDT-Pzt can be a powerful donor, which is favourable in the construction of a polymer donors for efficient PSCs.