The performance of new polymer solar cells based on thiophene and thienyl-quinoxaline with the post treatments

A new low band gap (optical band gap=1.62 eV) polymer (TTQ) based on thiophene and thienyl-quinoxaline by substituting phenyl in quinoxaline unit for thiophene rings was synthesized and characterized for application in polymer solar cells (PSCs). The optical band gap (E_g^opt) deduced from the onset (765 nm) of the polymer absorption spectrum in the films was 1.62 eV, which was less than those of the polymers TQ and FTQ and was closer to the ideal band gap of a donor for BHJ polymer solar cell applications. For the optimized polymer solar cell of TTQ:PC₇₁BM, 1:1 w/w, in DCB solution, a PCE over 1.41% with V_oc of 0.70 V, J_sc of 3.89 mA/cm², and fill factor (FF) of 55% under AM1.5 conditions was achieved by solvent annealing in comparing with those of solvent surface treatment devices (PCE of 1.34%) and thermal annealing devices (PCE of 1.10%).