Chiang Mai Journal of Science

Copolymer of 9,9- Di (2’ - ethylhexyl ) 2,7 dibromofluorene (BEH-PF) and dibromo (anthracene) were synthesized and used as an emissive polymer layer of organic light emitting devices at various compositions. The device structure consists of indium tin oxide (ITO) coated glass substrate, poly (3, 4-ethylenedioxythiophene/poly (styrene sulfonate) (PEDOTPSS) layer, emissive polymer layer and aluminium layer. The polymer layer was prepared by spin coating while the cathode aluminium layer was coated by vacuum evaporation. The photoluminescence spectrum peaks from BEH-PF solution locate at 416, 443 and 498 nm. While the luminescence spectra of copolymer solution are found only two peaks at 443 and 490 nm. The fabricated BEH-PF polymer film on quartz substrate shows the photoluminescence peaks at about 425, 444 and 516 nm, while the two photoluminescence peaks at about 445 and 495 nm appear in copolymer. In solution, the photoluminescence peak at 443 nm relatively decreases as the percentage of anthracene increases. However, this phenomena exhibits relative less effect for the coated film. Similarly, the concentration of polymer solution also affects the luminescence spectra of the copolymer. The electroluminescence spectra emitting from the fabricated devices give only slightly shift peak wavelengths from the photoluminescence peaks and the relative intensity is slightly affected by varying composition since the aggregation peak dominate in electroluminescence spectra.