Synthesis of Acenaphthyl and Phenanthrene Based Fused-Aromatic Thienopyrazine Co-Polymers for Photovoltaic and Thin Film Transistor Applications

Dithiopheric and fluorene co-polymers containing fused aromatic thieno[3,4-b]pyrazine moieties were synthesized for organic thin film transistor (OTFT) and organic photovoltaic (OPV) applications. Suzuki and Stille polycondensation reactions were used for the polymerization. The band gap (E-g) of the polymers was tuned in the range of 1.15-1.6 eV to match the solar spectrum. Density functional theory calculations were carried out to rationalize the low band gaps. These polymers showed field effect mobility (mu) as high as 0.2 cm(2)/(V.S) with an on/off ratio as high as 10(6) in OTFT devices. Interestingly, one polymer in this class also showed ambipolar charge transport. Power conversion efficiency (PCE) up to 1.3% was achieved in bulk heterojunction solar cells, indicating that these materials are promising for OPV applications.