Synthesis of polyfluorenes by oxidative polymerization, their characterization and implementation in organic solar cells

Abstract

Polyfluorene materials have demonstrated to be important components in the fabrication of organic solar cell devices, in both: the active and electron transport layers. The oxidative synthesis as well as optical and electrical properties of new polyfluorene copolymers containing 2,2′-(9,9-dioctyl-9H-fluorene-2,7-diyl) bistiophene and 3-alkylthiophene, alkyl = hexyl (PA1) and octyl (PA2) or 3,4-ethylenedioxythiophene (EDOT) (PM) were investigated. Changes in the HOMO–LUMO energy gap promoted for the insertion of EDOT ring were studied in thick film by using cyclic-voltammetry measurements and compared with the optical properties analyzed by UV–Visible spectroscopy. DFT calculations were used to investigate the possible electronic density distribution and conformational parameter for repetition units into the polymeric structure. Finally, these polymer were preliminary evaluated as donor materials into organic solar cells with architecture ITO/PEDOT:PSS/co-polymer:PC71BM/Field’s metal. Photovoltaic devices showed a very acceptable open circuit voltage (Voc) value, up to 0.92 V.