Synthesis and Photovoltaic Properties of Fluorene-Based Copolymers with Thiophene Heterocycle on the Side Chain
High molecular weight, readily soluable copolymer was prepared from 9,9-di (2-thienyl-hexyl) fluorene (TF) 2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9,9-di octyl fluorene and narrow band gap comonomer 2,3-dimethyl- 5,8-(5-bromo)-dithien-2-yl-quinoxalines (DTQU) using pallad- ium catalyzed Suzuki coupling methods. To compare the copolymer to this without thiophene in the C9 side chain of fluorene, the copolymer from DOF and DTQU was synthesized. The electrochemical, optical and photovoltaic properties of the copolymers were studied. The absorption spectra of the copolymers measured in thin films display two absorption peaks. The power conversion efficiency achieved in the device configuration ITO/PEDT/FT- DTQU:PCBM (1:2)/Al is 0.85% with open-circuit voltage (Voc) 0.8V. Further improvement by manipulating polymer/electrode interface and further investigation of more polyfluorene copolymers with narrow band gap aryl-hetero cycle units on the side chain is in progress.
Q. Hou et al., "Synthesis and Photovoltaic Properties of Fluorene-Based Copolymers with Thiophene Heterocycle on the Side Chain", Advanced Materials Research, Vols. 383-390, pp. 7677-7681, 2012