A new n-type semiconducting molecule with an asymmetric indenothiophene core for a high-performing non-fullerene type organic solar cell

Herein, a new asymmetric n-type semiconducting molecule (PhITBD) with an indenothiophene core was designed, synthesized using tethering 2-(benzo[c][1,2,5]-thiadiazol-4-ylmethylene)-malononitrile (BM) as terminal groups, and applied to polymer solar cells (PSCs). The PSCs with asymmetric PhITBD displayed improved power conversion efficiencies (PCE) of 6.57% as compared to those with the symmetric molecule IDT-2BM. The higher PCE value of the PhITBD-based PSC was mainly attributed to the enhanced photovoltaic properties, the V_oc, J_sc, FF induced by complementary light absorption (550-600 nm range), morphological improvement, and balanced charge carrier transport in the active layer. Due to the effective morphological control and absorption enhancement, asymmetric structured n-type-conjugated molecules are potential candidates for improving the performance of bulk heterojunction non-fullerene type PSCs.