Synthesis and Characterization of an Anthracene-Based Low Band Gap Polymer for Photovoltaic Devices

We have synthesized an anthracene-based conjugated polymer, poly[(9,10-bis(oct-1-ynyl) anthracene)-alt-(5,6-bis(octyloxy)-4,7-bis(thiophen-2-yl) benzo-[c][1,2,5]-thiadiazole)] (PANTBT), for application in organic photovoltaic devices. It exhibited a number average molecular weight of 14,300 g/mol and was fairly soluble in chlorinated organic solvents due to flexible octynyl-and octyloxy side chains on the anthracene and benzothiadiazole moieties. PANTBT showed absorption covering 300-660 nm. Through the bond alternation between the electron-sufficient anthracene (and thiophene) and electron-deficient benzothiadiazole units, a band gap of PANTBT was decreased to 1.89 eV, showing a deep HOMO level of -5.31 eV. As a result, PANTBT exhibited promising photovoltaic properties with a PCE value of 1.90% (V-oc = 0.77 V, J(sc) =-6.50 mA/cm(2), FF = 0.38) upon blending with PC71BM under AM 1.5G.