Synthesis of quinoxaline-based polymers with multiple electron-withdrawing groups for polymer solar cells

Abstract

Two quinoxaline-based conjugated polymers with multiple electron-withdrawing moieties were synthesized by the Stille coupling reaction for polymer solar cells (PSCs). For the construction of a typical donor-π-acceptor structure, the electron-donating indacenodithiophene (IDT) and indacenodithieno[3,2-b]thiophene (IDTT) were linked to the electron-withdrawing quinoxaline (DPQCF3F) that contained trifluoromethyl and fluorine units via a thiophene bridge to produce PIDT-Qx and PIDTT-Qx, respectively. Owing to the significant contribution of the DPQCF3F unit in the polymer backbone, Voc of the inverted-type PSCs was increased up to 0.92V. In addition, the replacement of two thiophenes of IDT to two thieno[3,2-b] thiophene units of IDTT in the quinoxaline-based polymer backbone can efficiently improved the light absroption and charge carrier mobility of the resultant polymer. Therefore, a higher PCE of 4.54% was achieved from the device based on PIDTT-Qx with a short circuit current density of 9.30mA/cm2, an open-circuit voltage of 0.92V, and a fill factor of 53%, compared with the device based on PIDT-Qx (2.83%).