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We prepared ternary organic solar cells (OSCs) by incorporating the medium wavelength absorption polymer PSEHTT into the PM6:L8-BO binary system. The power conversion efficiency (PCE) is improved from 15.83% to 16.66%. Although the fill factor (FF) is slightly reduced, the short-circuit current density (JSC) and open-circuit voltage (VOC) are significantly increased at the same time. A small amount of PSEHTT has a broad absorption spectrum in the short wavelength region and has good compatibility with PM6, which is conducive to fine-tuning the photon collection and improving the JSC. In addition, the highest occupied molecular orbital (HOMO) energy level of PSEHTT is deeper than that of PM6, which broadens the optical bandgap. This study provides an effective method to fabricate high-performance ternary OSCs by using a lower concentration of PSEHTT with PM6 as a hybrid donor material, which ensures a better surface and bulk morphology, improves photon collection, and broadens the optical bandgap. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ternary PSCs were fabricated with PBDB-TF as third component materials. • The improvement of charge dynamics process of ternary photoactive layer by ternary strategy. • The improved exciton-dissociation at the donor–blend acceptor interface. In this manuscripts, a ternary polymer solar cells (PSCs) are fabricate with two "D18-series" donor (D18-Cl and D18) as blend donor and T6 as acceptor. The effects of D18-Cl and D18 in ternary PSC on the film morphology, photoelectronic properties and charge carrier dynamics were systematically investigated. By finely adjusting the D18 content, a power conversion efficiency (PCE) of 16.66 % is achieved in the optimized ternary PSCs with 35 wt% D18 in donor, resulting from significantly improved short-circuit-current density (J SC) of 26.80 mA cm−2 in comparison with those of D18-Cl:Y6 binary PSCs. The J SC of ternary PSCs monotonously increase along with the incorporation of D18, indicating that D18 is comprehensively optimal short wavelength photon harvesting compared with D18-Cl. Both D18-Cl and D18 are shown similar highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels, which is beneficial to efficient charge transport at the blend donor domain. Our work indicates that the blend of D18-Cl and D18 as blend donor and Y6 as electron acceptor to boost photovoltaic performance in the ternary PSCs. [ABSTRACT FROM AUTHOR]