Multi-scale mechanical properties of bulk-heterojunction films in polymer solar cells

Abstract The mechanical properties of bulk-heterojunction (BHJ) films play critical roles in the operational stability of flexible polymer solar cells (PSCs). In this study, the multi-scale mechanical properties of the BHJ films containing three representative electron acceptors are systematically evaluated. Interestingly, the tensile moduli of the films based on PC 71 BM, Y6, and PRi-C39 decrease sequentially, and their fracture strain and toughness show an increasing trend. Moreover, the nanoindentation moduli of the films based on these acceptors vary in accordance with the results of tensile characterizations. Creep analyses illustrate that the occurrence of creep deformation in the PC 71 BM, Y6, and PRi-C39-based films decrease sequentially. Contact angle tests demonstrate that the donor-acceptor interactions greatly affect the mechanical properties of these films. All results above demonstrate the effects of acceptor type on the multi-scale mechanical properties of the BHJ films, which are important for the development of reliable flexible PSCs.