The status of the development of full-color polymer light emitting diodes will be presented. The focus of current materials research is on state-of-the-art red, green, and blue light-emitting polymers (LEP) with high efficiency, optimum color points, low driving voltages and long lifetimes in devices. A general overview of the progress of red, green and blue LEP lifetimes and efficiencies will be given and compared to requirements for both full-color passive and active matrix-displays for mobile display applications. Further, the status of ink-jet printing of LEPs for the industrialization of full-color displays will be discussed, and a comparison of the performance of spin coated and inkjet printed devices will be presented. In addition, two material-related topics studied recently will be discussed; namely, the lifetime of blue light-emitting devices correlated to processing, anodes, cathodes and the blue polymers themselves, and second, the consequences of pulsed-driving schemes on efficiency and lifetime.
Spin coating is a suitable technique for the fabrication of monochrome light-emitting polymer devices. For color displays, however, it is not the optimal solution when different polymers are applied. In principle, there are several technologies available for patterning light-emitting polymers. In this paper we discuss the advantages of drop-on-demand ink-jet printing over other printing methods. Special attention is given to some fundamental aspects of the printing process, such as drop formation and pixel filling. Examples of both monochrome and full color ink-jet printed passive matrix displays will be discussed.
This paper will given an overview of the current state of the art of polymer light-emitting devices as they are manufactured at Philips. Electro-optical characterization as well as lifetime measurements will be discussed, with emphasis on the use of electroluminescent polymer materials and processes in monochrome graphic displays. The factors that determine power consumption on a system level will be detailed. Initial results on inkjet-printed devices will be shown.