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dc.contributor.advisorSamuel, Ifor D. W.
dc.contributor.authorZhang, Shuyu
dc.coverage.spatialxviii, 228 p.en_US
dc.description.abstractThis thesis describes investigations into the optical and device design of organic light-emitting diodes (OLEDs) with the aim of exploring the factors controlling the spatial emission pattern of OLEDs and developing novel OLEDs with directional emission by applying wavelength-scale photonic microstructure. The development of directional OLEDs was broken down into two steps: the development of efficient narrow linewidth OLEDs and the integration of wavelength-scale photonic microstructures into narrow linewidth OLEDs. The narrow linewidth OLEDs were developed using europium (Eu) complexes. The electrical optimisation of solution-processed Eu-based OLEDs using commercially available materials was investigated. The optimised Eu-based OLEDs gave an external quantum efficiency of 4.3% at a display brightness of 100 cd/m². To our knowledge, this is the highest efficiency reported for solution-processed Eu-based OLED devices, and the efficiency roll-off has been reduced compared with other reported references. Photonic microstructures were applied to develop directional OLEDs using the efficient Eu-based OLEDs. Two contrasting strategies were used. One was to embed photonic microstructures into Eu-based OLEDs, the other was to couple photonic microstructures externally onto the devices. The microstructured devices developed by the former strategy boosted the emitted power in desired angles in both s- and p-polarisations and doubled the fraction of emission in an angle range of 4⁰. The devices developed by the external coupling strategy achieved even higher directionality and the out-coupled emission was a confined beam with easy control of beam steering. Around 90% of the emitted power was confined in an angular range of 20⁰ in the detection plane. The optical properties can be optimised independently without compromising the electrical properties of devices, which gives major advantages in terms of effectiveness and versatility. Optical models were also developed to investigate the out-coupling mechanism of various trapped modes and develop OLEDs with stronger directionality.en_US
dc.publisherUniversity of St Andrews
dc.subjectOrganic light-emitting diodeen_US
dc.subjectPhotonic microstructureen_US
dc.subjectDirectional emissionen_US
dc.subjectNarrow linewidth emitteren_US
dc.subjectEuropium complexen_US
dc.subjectOptical modellingen_US
dc.subjectDiffractive opticsen_US
dc.subjectSoft lithographyen_US
dc.subject.lcshLight-emitting diodesen_US
dc.subject.lcshOrganic thin filmsen_US
dc.titleDirectional organic light-emitting diodes using photonic microstructureen_US
dc.contributor.sponsorScottish Universities Physics Alliance (SUPA)en_US
dc.type.qualificationnamePhD Doctor of Philosophyen_US
dc.publisher.institutionThe University of St Andrewsen_US
dc.rights.embargoreasonThesis restricted in accordance with University regulations. Electronic copy restricted until 6th October 2018en_US

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