New series of highly phenyl-substituted polyfluorene derivatives for polymer light-emitting diodes

A new series of highly phenyl-substituted polyfluorene derivatives were synthesized and characterized. The resulting polymers were amorphous and showed excellent solubility in common organic solvents, such as chloroform, tetrahydrofuran, xylene, toluene, chlorobenzene, and so forth. All possessed satisfied thermal stability with glass-transition temperatures (T-g's) in the range of 79-115 degreesC. They emitted blue light with photoluminescent (PL) maximum peaks at about 408-412 nm in thin films. The PL efficiencies of the polymer films were measured around 30-33%. The highly phenylated pendants improved the T-g of polyfluorene without forming defects in the polymers and reduced their tendency to form aggregate/excimers. Polymer light-emitting diodes were fabricated from these polymers with the configuration of indium tin oxide/polyethylenedioxythiophene:polystyrene sulfonic acid/polymer/Ba/Al, which emitted bright blue light with maximum peaks at 418-420 nm. The maximum external quantum efficiencies of these devices were 0.41-0.6%. (C) 2004 Wiley Periodicals, Inc.