Improved external coupling efficiency in organic light-emittingdevices on high-index substrates

摘要

High-index-of-refraction substrates are shown theoretically andexperimentally to increase the external coupling efficiency of organiclight-emitting devices (OLEDs) by using a quantum mechanical microcavitymodel. This increase is due to the elimination of those modes waveguidedin the ITO/organic layer. Bi-layer OLEDs were fabricated on standardsoda lime glass and high-index glass substrates, and their far-fieldintensity pattern was measured. Among the devices optimized for externalefficiency, those on shaped high-index substrates exhibited a 53%improvement in external quantum efficiency over the devices on shapedstandard glass substrates, and an increase by a factor of 2-3 times overthose on planar glass substrates. This principle is applicable to anybackside patterning technique in conjunction with other OLED structuralimprovements