New Poly(arylene vinylene)s Based on Diketopyrrolopyrrole for Ambipolar Transistors

Three diketopyrrolopyrrole-based donor acceptor copolymer semiconductors were synthesized by Stile coupling polymerization and their structural, photophysical, electrochemical, and field-effect charge transport properties were characterized. The new copolymers, poly[3,6-(2,5-bis(2-hexyldecyl)pyrrolo[3,4-c]pyrrole-1,4-dione)-alt-1,2-bis-(2'-thienyl)vinyl-5',5 ''-diyl] (HD-PPTV), poly[3,6-(2,5-bis(2-hexyldecyl)pyrrolo[3,4-c]pyrrole-1,4-dione)-alt-1,2-bisphenylvinyl-4',4 ''-diyl] (HD-PPPV), and a 50:50 random copolymer (PPTPV), have moderate number-average molecular weights (21800-88800 g/mol). The copolymers have optical absorption bands in the visible to near-IR regions with optical bandgaps that varied from 1.22 eV for HD-PPTV to 2.0 eV for HD-PPPV. Ionization potentials of 5.14-5.48 eV and electron affinities of 3.13-3.34 eV were derived from cyclic voltammetry. Ambipolar charge transport was seen in transistors based on HD-PPTV and PPTPV, whereas only hole transport was observed in HD-PPPV. Field-effect transistors fabricated from HD-PPTV had hole and electron mobilities as high as 0.2 and 0.03 cm(2) V(-1) s(-1). Integration of the ambipolar HD-PPTV transistors into complementary inverters demonstrated sharp switching characteristics with large voltage gains of up to 27.