Material and interface engineering for high efficiency light-emitting devices

Our effort in improving the performance of light-emitting materials and devices have been focused on three main areas: 1) modify the interface between light-emitting polymers and electrodes for better charge injection; 2) develop in-situ crosslinkable hole-transporting polymers to facilitate multilayer solution processing and cascade hole-injection and transport; and 3)enhance the efficiency of polymer LEDs through the development of new conjugated materials with balanced charge-transporting properties. In this talk, we will review our recent progress using dipolar self-assemble monolayer (SAM) to form dense assembly on indium tin oxide (ITO)to tune the energy barrier between ITO and hole-transporting polymers. We have systematically determined these barriers using the internal photoemission technique. Several in-situ polymerizable hole-transporting materials with desirable energy level were also developed to facilitate cascade hole-injection for quantum dot (QD)- and blue phosphorescent dopant-based LEDs. In addition to these efforts, a series of neutral surfactants were also employed to modify the energy barrier between light-emitting layer and several high work function cathodes, such asAl, Ag and Au. As a result of this integrated materials development approach, stable, very efficient and bright light-emitting devices have been demonstrated for applications in displays and solid-state lighting.

© 2007 APS DLS