Solution processable benzotriazole and fluorene containing copolymers for photovoltaic applications

2-Dodecyl benzotriazole and 9,9-dioctylfluorene containing alternating copolymers poly((9,9-dioctylfluorene)-2,7-diyl-(2-dodecyl-benzo[1,2,3]triazole)) (P1), poly((9,9-dioctylfluorene)-2,7-diyl-(4,7-bis(thien-2-yl) 2-dodecyl-benzo[1,2,3]triazole)) (P2), poly((9,9-dioctylfluorene)-2,7-diyl-(4,7-bis(3-hexylthien-5-yl) 2-dodecyl benzo[1,2,3]triazole)) (P3) were synthesized via a typical Suzuki coupling polymerization. UV-vis and electrochemical studies indicated that polymers have desirable HOMO-LUMO and band gap energy levels, enabling efficient electron transfer when blending them with fullerene derivatives. Photovoltaic properties of the copolymers mixed with [6,6] phenyl-C61-butyric acid methyl ester (PCBM), were investigated. P2 exhibited the best device performance with an open circuit voltage of 0.6 V. short circuit current of 3.4 mA/cm(2) and power conversion efficiency of 0.56% under Air mass 1.5 Global (AM 1.5G, 100 mW/cm(2)) illumination. Hole mobilities of the polymers were calculated using space charge limited current (SCLC) method and found to be in the order of 10(-5) for P1 and P2 and 10(-4) for P3. (C) 2012 Elsevier B.V. All rights reserved.