Ternary organic photovoltaics (OPVs) are fabricated with PBDB-T-2F as the donor and a blend of FOIC and IT-2F as the acceptor. The optimized ternary OPV with the blended materials of FOIC and IT-2F (the ratio of FOIC:IT-2F is 0.7:0.3) as the blended acceptor exhibits a PCE of 13.95%, which is attributed to enhancing photon harvesting and improving exciton utilization through energy transfer between the donor and blended acceptor. The photoluminescence spectra and time-resolved photoluminescence curve of the blended FOIC and IT-2F confirm that energy transfer occurs at the IT-2F/FOIC interface. This result is favorable for achieving high short-circuit current density. It should be highlighted that the higher fill factor for optimized ternary OPVs than those of the two binary OPVs can be attributed to the smooth surface of the blended films and balanced charge transport of the ternary photoactive layers. Simultaneously, the optimized ternary OPV exhibits better thermal stability capability, which is significantly higher than those of the PBDB-T-2F:FOIC binary OPVs. This work indicates that the photovoltaic performance and stability of ternary OPVs can be well-optimized by carefully selecting materials and adjusting the ratio of the used materials.