Flexible linker-based dimer donor for highly efficient and thermally stable organic solar cells

Abstract

Simultaneously realizing high power conversion efficiency (PCE), batch reproducibility, and device stability remain challenging in the structural design of donor materials for organic solar cells. Herein, we report a giant molecule donor (GMD) Dimer-C6, constructed by hexyl-bridged dimerization of two small-molecule donor (SMD) units, MPhS-C6. Benefiting from its enlarged molecular size and the structure combining rigidity and flexibility, Dimer-C6 exhibits enhanced thermal-driven assembly behavior and improved thermal stability. After the one-step thermal annealing (TA) treatment, Dimer-C6:Y6 device achieves a PCE of 13.22%, outperforming MPhS-C6:Y6 (12.64%), while maintaining 90% of the initial PCE after continuous heating at 80°C for 168h, demonstrating excellent thermal stability. This enhanced performance originates from a unique “pre-aggregation to adaptive packing” mechanism during solution-to-film transformation of the alkyl-tethered-dimer architecture, which is associated with the synergistic optimization of assembly adaptability and morphological stability. Moreover, an optimized two-step TA strategy further elevates the PCE to 13.78%. This work highlights the advantages of dimerized SMD design and provides a rational strategy for developing donors with improved efficiency, reproducibility, and stability.

Keywords

dimer / giant molecule donor / flexible linker / end-to-end tethered / thermal stability

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