A photoluminescence and electroluminescence study of the properties of polyfluorene copolymers for display applications

Optical and electrical characterizations of 2 series of polyfluorene copolymers which are p(F8-co-27DBTO)s and p(F8-36DBT)s including 5 different units' percentages each are reported. The optical properties of them in solution, film are characterized principally by using the techniques of absorption and emission spectra. The effects of changing the concentration of the new unit in the polyfluorene copolymers are investigated by comparing the absorption and PL emission spectra of them in solution and solid state. The preparation of electroluminescent device using these copolymers as the active layer is reported. The external quantum efficiency and other characteristics such as brightness and turn-on voltage using the LEDs test system are presented. The effects of extending the width of spectrum, shifting the EL wavelength and enhancing quantum yield by the new units are presented. The variations in external quantum efficiency and EL spectrum of devices with different thicknesses of the light-emitting layer are reported and analysed.