Ternary organic solar cells (TOSCs), consisting of a donor polymer (D) and two acceptor (A₁ and A₂) materials (D:A₁:A₂), exhibit significant potential for overcoming the efficiency constraints of binary systems. It starts with the advantages of the binary blends of a donor (polymer) and an acceptor material (fullerene or non-fullerene acceptor) in heterojunction-based solar cells and integrates them with the strengths of tandem solar cells. The actual intrinsic challenges (limited spectrum absorption, charge carrier mobilities, efficient exciton dissociation, significant recombination losses, charge carrier collection, etc.) can be materialized here by the introduction of the third component, PCBM. The impact of PCBM as a third component (A₂) on charge carrier mobility in ternary blends—a crucial factor influencing device performance—is evaluated in this paper. The parallel model best describes the transport mechanism in the D:A₁:A₂ matrix, where the active layer acts as two intercalated bilayers. The third element's role as an electron transfer channel emphasizes the importance of compound compatibility and miscibility, also contributing to enhancing the charge carrier mobility. By systematically varying the ratio of the two acceptors (A₁:A₂) while maintaining a constant D:A ratio, the impact of compositional changes on charge transport properties is explored. Using the CELIV method, charge carrier mobility along with other important electrical properties (charge density and relaxation time) are examined. A significant correlation between charge carrier mobility and the acceptor ratio is revealed. These results underscore the importance of fine-tuning the ternary blend composition to maximize charge transport and, consequently, device efficiency. The insights gained from this study provide valuable guidance for the rational design of high-performance ternary OSCs.

Acknowledgments: This work was supported by a grant of the "Alexandru Ioan Cuza" University of Iasi, within the Research Grants program, Grant UAIC, code GI-UAIC-2021-07.