Two compatible nonfullerene acceptors with similar structures as alloy for efficient ternary polymer solar cells

In this work, we fabricated high efficient ternary PSCs based on two compatible non-fullerene acceptors (IDIC and ITIC) with similar chemical structures and one new D-A-type polymer (PSTZ) donor. By inserting ITIC into the binary PSTZ:IDIC system, the active layer show smooth and gradient energy levels, improved crystallinity and optimized morphologies, which results in efficient exciton separation, charge transport and collection. As a result, the optimal ternary PSCs based on PSTZ:ITIC:IDIC (1:0.1:0.9) exhibited a higher PCE of 11.1% with a V_oc of 0.953 V, J_sc of 17.4 mA cm⁻² and FF of 66.9% in comparison with those of binary PSC systems based on PSTZ:IDIC (PCE of 8.06%) or PSTZ:ITIC (PCE of 8.13%). These results indicate that combining two compatible nonfullerene acceptors with similar structures to fabricate ternary PSCs should be a promising strategy to enhance the photovoltaic performance of the PSCs.