A blue electroluminescent polymer, poly(biphenylenevinylene) derivative containing a bulky fluorenyl group, was prepared by the nickel-catalyzed coupling reaction. The structure and properties of the polymer, PBPHFV, were analyzed by various spectroscopic methods. The obtained polymer had good solubility and thermal stability. The polymer film showed maximum absorption and emission peaks at 370 and 485 nm, respectively. A blue electroluminescence (λ max ) 465 nm) was obtained with intensities of 4116 cd/m 2 when the light-emitting diodes of ITO/PEDOT/PBPHFV/LiF/Al were fabricated. The maximum efficiency of the devices was 0.22 lm/W with a turn-on voltage of 4.3 V. With the optimum ratio of PBPHFV to PVK as 1:5, the luminance and efficiency of the devices reached up to 9342 cd/m 2 and 1.66 lm/W, respectively.

The sterically hindered and highly thermal stable spirobifluorenyl-substituted poly(pphenylenevinylene) derivative was synthesized by Gilch polymerization. The defect-free polymer structure was characterized by various spectroscopies. The polymer was completely soluble in common organic solvents, and it had high thermal stability with high T g of 205 °C. The polymer film showed maximum emission at 515 nm with a shoulder peak at around 560 nm and showed photoluminescence efficiency of 26 ( 5%. The study of thermal annealing of PL spectrum showed inhibited excimer formation. A cyclic voltammetry study revealed that the HOMO and LUMO energy level of the polymer are 3.08 and 5.46 eV, respectively. The EL spectrum from the device using polymer as emitting material showed a maximum peak of 515 nm, corresponding to the green region (x ) 0.31, y ) 0.61) in CIE (Commission Internationale de l'Eclairage) chromaticity coordinates. The LED based on polymer was shown to have a maximum brightness of 1155 cd/m 2 at 12.6 V and a maximum power efficiency of 0.118 lm/W (143 cd/m 2 , 7.8 V, 1.67 mA).

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