Non-fullerene acceptors with heteroatom substitution on the core moiety for efficient organic photovoltaics

Organic photovoltaics (OPVs) represent one of the most promising photovoltaic technologies owing to their high capacity to convert solar energy to electricity. With the continuous structure upgradation of photovoltaic materials, especially that of non-fullerene acceptors (NFAs), the OPV field has witnessed rapid progress with power conversion efficiency (PCE) exceeding 19%. However, it remains challenging to overcome the intrinsic trade-off between the photocurrent and photovoltage, restricting the further promotion of the OPV efficiency. In this regard, it is urgent to further tailor the structure of NFAs to broaden their absorption spectra while mitigating the energy loss of relevant devices concomitantly. Heteroatom substitution on the fused-ring π-core of NFAs is an efficient way to achieve this goal. In addition to improve the near-infrared light harvest by strengthening the intramolecular charge transfer, it can also enhance the molecular stacking via forming multiple noncovalent interactions, which is favorable for reducing the energetic disorder. Therefore, in this review we focus on the design rules of NFAs, including the polymerized NFAs, of which the core moiety is substituted by various kinds of heteroatoms. We also afford a comprehensive understanding on the structure–property−performance relationships of these NFAs. Finally, we anticipate the challenges restricting the efficiency promotion and industrial utilization of OPV, and provide potential solutions based on the further heteroatom optimization on NFA core-moiety.