Organic solar cells (OSCs) are considered as a promising next-generation photovoltaic technology because of their light weight, flexibility, and the potential of roll-to-roll fabrication. However, the relatively large energy loss (E_loss) from the optical bandgap (E_g) of the absorber to the open-circuit voltage (V_oc) of the device hinders further improvement of the PCEs of OSCs. Here, we report efficient non-fullerene all-small-molecule organic solar cells (NF all-SMOSCs), using DR3TBDTT and O-IDTBR as the donor and acceptor, respectively. We obtain a high electroluminescence yield (EQE_EL) value of up to ∼4 × 10⁻⁴ corresponding to a 0.21 eV non-radiative recombination loss, which is the smallest value for bulk-heterojunction (BHJ) OSCs so far. As a result, a low E_loss of 0.54 eV and a considerably high V_oc of 1.15 V are obtained for BHJ NF all-SMOSCs.

Introduction of diCN-substitution can lower the HOMO and improve the miscibility between diCN-USQ and PC₇₁BM, leading to higher PCE.