Conjugated Polymers Based on a S- and N-Containing Heteroarene: Synthesis, Characterization, and Semiconducting Properties

Three alternating conjugated polymers (P-bTC10, P-bTC12, and P-bTC16) comprising a novel S- and N-containing heteroarene, i.e., N-dodecyldithieno[2,3-b;7,6-b]carbazole, and 4,4'-dialkyl-2,2'-bithiophenes have been designed and synthesized. The nitrogen atom in the heteroarene allows introducing an additional alkyl substituent in each repeating unit of the polymers. The resulting polymers are thermally stable with decomposition temperature of similar to 400 degrees C and highly soluble in various organic solvents, such as tetrahydrofuran (THF), toluene, chloroform, and chlorobenzene, etc. Bottom gate, top contact OTFT devices were fabricated by solution casting. Mobility of the devices increased with an increase of the alkyl chain length in bithiophene units, and P-bTC10, P-bTC12, and P-bTC16 exhibited the mobilities up to 0.0064, 0.022, and 0.035 cm(2)/(V s), respectively. The mobility of P-bTC16 is comparable to that of regioregular poly(3-hexylthiophene) (rr-P3HT) reference devices, indicating that this heteroarene is a potential building block for high-mobility conjugated polymers.