Poly(p-phenylenevinylene) presenting pendent pentaphenylene dendron groups for light-emitting diodes

Abstract

We have synthesized, using the Gilch method, a novel poly(p-phenylenevinylene) derivative (PPV-PP) containing two pendent pentaphenylene dendritic wedges, and have characterized its structure and properties. The incorporated side chain pentaphenylene dendrons serve as solubilizing groups, prevent pi-stacking interactions from occurring between the polymer main chains, and suppress the formation of excimers in the solid state. Photoluminescence studies indicate that efficient intramolecular energy transfer occurred from the photoexcited pentaphenylene groups to the poly(p-phenylenevinylene) backbone. The polymer film exhibits a maximum emission at 510 nm and had a photoluminescence efficiency of 46%, which is similar to that measured in dilute solution. The photoluminescence spectra remained almost unchanged after thermal annealing at 150 degrees]C for 20 h, and displayed inhibited excimer formation. Polymer light-emitting diodes that we fabricated in the configuration ITO/PEDOT/PPV-PP/Mg:Ag/Ag exhibited a maximum emission peak at 513 nm, corresponding to the green region [x = 0.30 and y = 0.62 in the Commission Internationale de L'Eclairage (CIE) chromaticity coordinates]. The maximum brightness and maximum luminance efficiency were 1562 cd/m(2) and 1.93 cd/A, respectively. (c) 2005 Wiley Periodicals, Inc.