The influence of numbers of subunits on the photovoltaic performance of non-fullerene acceptors

•Two new acceptors SF-2IIG and SF-4IIG were designed and synthesized.•The effects of the number of the electron deficient building blocks on several characters were investigated.•Increasing the numbers of IIG building blocks is beneficial to photovoltaic performance to achieve 220% enhancement.•This result demonstrated a strategy of achieving high efficient non-fullerene solar cells.

Two new small-molecular acceptors SF-2IIG and SF-4IIG were designed and synthesized to investigate the influence of the numbers of electron-deficient subunits of non-fullerene acceptors on the efficencies of photovotaic devices. The studies showed that these two acceptors have different optical absorbption, energy levels, charge transport mobilities. As a result, the efficiencies of SF-4IIG based solar cells are significantly higher than those of SF-2IIG based ones.