A 1,8-naphthalimide based small molecular acceptor for polymer solar cells with high open circuit voltage

A novel small molecule NI-T-NI with a thiophene core and two 1,8-naphthalimide terminal groups was synthesized via direct C-H activation and used as the acceptor for polymer solar cells. NI-T-NI exhibits a good crystallinity and can form H-aggregates in the solid state. NI-T-NI has a rather high-lying LUMO level, which is beneficial for achieving a high V-OC. In cooperation with a high-lying LUMO level polymer PCDTBT-C12, a PCE of 2.01% with a high V-OC of 1.30 V has been achieved. As far as we know, a V-OC of 1.30 V is the highest value reported for single junction organic solar cells. Our results have demonstrated that 1,8-naphthalimide could be a useful building block for the synthesis of promising acceptor materials for polymer solar cells.