Interface Control of Polymer-Based Light-Emitting Devices
Bilayer and multilayer polymer structures provide opportunities for new photophysics and new types of light emitting devices. Photoluminescent and electroluminescent studies of bilayer heterojunctions formed from a poly(pyridyl vinylene phenylene vinylene) (PPyVPV) derivative and poly(vinyl carbazole) (PVK) show an emission peak which cannot be ascribed to either the PPyVPV derivative or PVK layer. Through studies of absorption and photoluminescence excitation (PLE) spectra we demonstrated that the additional feature results from an exciplex at the bilayer interface. The photoluminescence efficiency of the exciplex is greater than 20%. We also discuss here the fabrication of color variable bipolar/ac light-emitting devices based on conjugated polymers. The devices consist of blends of pyridine-phenylene and thiophene-phenylene based copolymers sandwiched between the emeraldine base form and the sulfonated form of polyaniline. ITO and Al are used as electrodes. The devices operate under either polarity of driving voltage with different colors of light being emitted, red under forward bias, and green under reverse bias.
KeywordsReverse Bias Forward Bias Emission Energy Emeraldine Base Redox Polymer
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