High-efficiency polyfluorene polymers suitable for RGB applications
We report recent results on a range of poly(fluorene)-based polymer light emitting diodes (PLEDs). These have been developed for a wide range of emission colours with a common device architecture. This approach achieves facile injection of both electrons and holes and features polymers with common core chemistry. A concern is to ensure that the PLED's emission colour is suitable for use in full colour display applications. By varying the chemistry of the emissive layer the emission colour is tunable with little compromise of the electrical performance whilst retaining the general device architecture. This approach has enabled rapid development of the different PLED colours and demonstrated efficient, stable EL emission at various wavelengths. We are now able to demonstrate significant device efficiencies for red, green and blue PLEDs using bilayer structures on indium–tin oxide substrates with evaporated metal cathodes. For example, green-light-emitting structures with efficiencies in excess of 20 lm/W can be regularly produced.