Conjugated polymer consisting of quinacridone and benzothiadiazole as donor materials for organic photovoltaics: Coplanar property of polymer backbone

摘要

Highly soluble poly[quinacridone-alt-benzothiadiazole] (PQCDTB) has been synthesized through the Suzuki coupling reaction by introducing planar quinacridone and highly absorbing benzothiadiazole. The PQCDTB dissolved in general organic solvents, and the M _n was 49.8 kg/mol. The optical band gap energy was 1.92 eV, which was similar to the band gap of benzothiadiazole. The HOMO and LUMO levels of PQCDTB were -5.24 eV and -3.32 _eV, respectively. According to the XRD measurement, PQCDTB showed the formation of ordered lamellar structure as an out-of-plane peak (h00) by the alkyl side chain of quinacridone and conventional edge-on π- stacking. This study also evaluated the OPV characteristics by fabricating a bulk-heterojunction-type polymer solar cell. When PQCDTB and PC _(71)BM were fabricated in a 1:1 weight ratio, the open-circuit voltage (V _(OC)), short-circuit current (J _(SC)), fill factor (FF), and power conversion efficiency (PCE) were 0.79 V, 5.6 mA cm ~(-2), 55.8% and 2.5%, respectively. In particular, PQCDTB exhibited higher FFs compared with poly[carbazole-alt-benzothiadiazole] (PCZDTB).