A narrow bandgap conjugated polymer poly(2-(5-(5,6-bis(octyloxy)-4-(thiophen-2yl)benzo[c]) [1,2,5]thiadiazol-7-yl)thiophen-2-yl)-vinylene), POTBTV, was synthesized by a Pd-catalyzed Stille-coupling method, for application as donor material in polymer solar cells (PSCs). The polymer possesses good thermal stability and reasonable solubility. The absorption edge of POTBTV film is at 750 nm, indicating a narrow band gap of 1.65 eV. The HOMO and LUMO energy levels of POTBTV are −4.97 eV and −2.99 eV, respectively. The power conversion efficiency (PCE) of the PSC based on POTBTV as the donor PC70BM as the acceptor reached 1.53% with a short circuit current density of 6.83 mA cm−2, an open circuit voltage of 0.6V and a fill factor of 0.374 under the illumination of AM1.5, 100 mW cm−2, which is among the highest PCE values for PSCs based on PTV derivatives.
