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theses

Organic light-emitting devices (OLEDs) are used in flat panel displays such as televisions and cell phones. OLEDs have superior color purity, image quality, and flexibility, and less pixelation than traditional LCDs. OLEDs use fluorescent and/or phosphorescent materials in their emissive layer. Fluorescence emits from the singlet state, and can only emit up to 25% of the excitons. Phosphorescence can emit three times the amount of excitons as fluorescence due to its ability to emit from the singlet and triplet state, and therefore can emit 100% of the excitons, in theory. Although phosphorescence has greater efficiency than fluorescence, blue phosphorescent material is currently replaced in OLEDs with fluorescent material due to the instability of blue phosphorescent materials caused by triplet exciton quenching processes and chemicals. Various approaches have been developed to improve the stability of such phosphors including passivation, development of new organometallic molecules, and control of host-dopant composition in thin films. Here, we demonstrate an extrinsic approach to improving the photostability of blue organometallic phosphors that employs photoluminescence lifetime reductions caused by the local electric fields of plasmonic surfaces. We show that the decay rate of phosphorescence is increased on certain plasmonic surfaces, which improves the stability of a common blue organometallic phosphor. This approach is distinctive because it involves modification to the local electromagnetic environment of the phosphor rather than modifications to the phosphor molecular structure or to the emitting material composition. Future studies will further examine the Purcell Effect’s impact on blue phosphorescent materials using silver and gold discrete nanoparticles. More work should be done to confirm the mechanism increasing stability, and testing the blue organic phosphorescent material coated nanostructures in devices. For increased commercial and financial production feasibility, a large scale solution processing method should be created.

ETD_10894

doi:10.7282/t3-hdj3-1q93

M.S.

Includes bibliographical references

ETD graduate

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