Wide Band Gap Polymer Based on Indacenodithiophene and Acenaphthoquinoxaline for Efficient Polymer Solar Cells Application

A new wide band gap polymer PIDT-AQx with indacenodithiophene (IDT) as the electron-rich unit and acenaphthoquinoxaline (AQx) as the electron-deficient unit has been designed and synthesized. The optical band gap of PIDT-AQx was 1.81 eV with a HOMO energy level of −5.13 eV. Polymer solar cells with the blend of PIDT-AQx/PC(71)BM as the active layer achieved a power conversion efficiency (PCE) of 4.56%, with an open-circuit voltage (V(oc)) of 0.84 V, a current density (J(sc)) of 9.88 mA cm(−2), and a fill factor (FF) of 55% without any solvent additives and pre- or post-treatments. The photovoltaic performance of PIDT-AQx could be slightly improved with a PCE up to 4.78% after thermal annealing due to enhanced J(sc). The results indicate that acenaphthoquinoxaline is a promising building block for developing conjugated polymers for efficient solar cells application.