Alternating copolymers of electron-rich arylamine and electron-deficient 2,1,3-benzothiadiazole: Synthesis, characterization and photovoltaic properties

A series of alternating copolymers of electron-rich arylamine and electron-deficient 2,1,3-benzothiadiazole (BT), PV-BT, DP-BT, and TP-BT, were synthesized by Heck coupling reaction. UV-vis absorption and fluorescence spectra show that the copolymerization of electron-rich diphenylamine (DP), triphenylamine (TP), MEH-PV (PV), and electron-deficient BT results in low-bandgap conjugated polymers. Within the three copolymers of PV-BT, DP-BT, and TP-BT, TP-BT possesses the highest hole mobility of 4.68 × 10 ^-5 cm²/V, as determined from the space charge limited current (SCLC) model. The bulk heterojunction-typed polymer solar cells (PSCs) were fabricated with the blend of the copolymers and PCBM as the photosensitive layer. The power conversion efficiencies (PCE) of the PSCs based on PV-BT, DP-BT, and TP-BT reached 0.26%, 0.39%, and 0.52%, respectively, under the illumination of AM 1.5, 100 mW/cm². The results indicate that TP-BT is a promising photovoltaic polymer for PSCs.