Energy transfer in polyfluorene copolymer used for white-light organic light emitting device

Luminescence properties of a type of polyfluorene copolymer (PFO-DBT5) used for white-light organic light emitting device (OLED) were studied and discussed, in which a very low concentration of 0.05 mol% 4,7-bithienyl-2,1,3-benzothiadiazole (DBT) molecules were inserted in polyfluorene chain as orange-light unit. From the spectroscopic analysis of PFO-DBT5 in solution and nanoparticles, it is concluded that inter-chain Forster energy transfer from polyfluorene segments to DBT units play major role in process of white-light emission of PFO-DBT5. By measurement of electroluminescent properties, it is found that annealing of PFO-DBT5 film in vacuum is favorable for improving white-light emission owing to enhancement in inter-chain Forster energy transfer. CIE coordinates (0.38, 0.33) were obtained under the annealing temperature of 140 degrees C. It was found that the annealing temperature affects the luminance and efficiency of white-light OLED. The optimum annealing temperature was 100 degrees C. (c) 2013 Elsevier B.V. All rights reserved.