New Low Bandgap Conjugated Polymer Derived from

ABSTRACT: To develop conjugated polymers with low bandgap, deep HOMO level, and good solubility, a new conjugated alternating copolymer PC-DODTBT based on N-90-heptadecanyl-2,7-carbazole and 5, 6-bis(octyloxy)-4,7-di(thiophen-2-yl)benzothiadiazole was synthesized by Suzuki cross-coupling polymerization reaction. The polymer reveals excellent solubility and thermal stability with the decomposi-tion temperature (5 % weight loss) of 327C. The HOMO level of PC-DODTBT is-5.11 eV, indicating that the polymer has relatively deep HOMO level. The hole mobility of PC-DODTBT as deduced from SCLC method was found to be 2.03 104 cm2/Versus Polymer solar cells (PSCs) based on the blends of PC-DODTBT and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) with a weight ratio of 1:2.5 were fabri-cated. Under AM 1.5 (AM, air mass), 100 mW/cm2 illumina-tion, the devices were found to exhibit an open-circuit voltage (Voc) of 0.73 V, short-circuit current density (Jsc) of 5.63 mA/ cm2, and a power conversion efficiency (PCE) of 1.44%. This photovoltaic performance indicates that the copolymer is promising for polymer solar cells applications. VC 2011 Wile