Phosphorescent OLED technology

Hack, M., Weaver, M. S., and Adamovich, V. 2005. Status and potential for phosphorescent OLED technology. Proc. SPIE 5961 596102-1. 

For reasons clear from the introduction, enhancement of phosphorescence is a particularly attractive application of plasmonics to OLED technology. Since carriers are injected into an OLED from separate contracts, their spins are uncorrelated and spin statistics dictate preferential formation of triplet excited states. Since these are generally poor emitters at ambient temperature, metallic enhancement of the phosphorescent rate would be desirable. Moreover, triplet states are typically long-lived and prone to oxidation reactions so that reduction of the triplet lifetime could potentially improve stability of the phosphors. PtOEP is a model phosphor and its application to electroluminescence was pioneered by the groups of Forrest and Thomson (46-47). We have investigated plasmonic enhancement of the PtOEP phosphorescence on silver surfaces prepared using the Tollens reaction. Dilute PtOEP in a polymer binder was spin cast onto substrates with various densities of nanotextured silver and assumed to deposit conformally, the spin speed being used to control the approximate thickness of the overlayer. 

The luminous efficiency of OLEDs can be improved Imther by use of phosphorescent emissive materials. Incorporated into OLED devices starting in the 1990s, phosphorescent dopants have a potential to achieve 100% internal quantum efficiency. We will describe materials and architecture developments of phosphorescent OLED devices in Section 14.4. Finally, we discuss the future outlook of the OLED technology in Section 14.5. 

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