Thienobenzene-fused perylene bisimide as a non-fullerene acceptor for organic solar cells with a high open-circuit voltage and power conversion efficiency

Perylene bisimide (PBI) based molecules have recently attracted tremendous interest as acceptors in non-fullerene organic solar cells. However, most PBI-based acceptors possess deep LUMO energy levels (-3.9 ∼ -4.0 eV) and show an open-circuit voltage (V_oc) below 0.90 V, thus limiting the improvement of device efficiency. Here, we report two novel ring-fused PBI dimers, SdiPBI-BT and diPBI-BT, with thienobenzene fused to the bay region of the PBI subunits. Conventional bulk-heterojunction (BHJ) solar cells based on SdiPBI-BT show a power conversion efficiency (PCE) of 6.71% with a high V_oc value of 0.95 V, a short-circuit current density (J_sc) of 10.31 mA cm^-2 and a high fill factor (FF) of 68.7%. Devices based on diPBI-BT show a PCE of 5.84% with a high V_oc value of 0.99 V. These results demonstrate that ring-fused PBI derivatives are promising materials for non-fullerene cells.