The role of spin in triplet-triplet annihilation upconversion

dc.contributor.advisor Timothy, Schmidt en_US
dc.contributor.advisor Dane, McCamey en_US Danos, Andrew en_US 2022-03-15T08:27:23Z 2022-03-15T08:27:23Z 2017 en_US
dc.description.abstract Chemical systems that exhibit photochemical upconversion via triplet triplet annihilation have been studied using a range of fluorescence, absorption, and magnetic spectroscopy techniques. Each part of this investigation furthers understanding of how the emitter properties govern both the efficiency of the overall upconversion process, and the spin dependent annihilation step. Developing this fundamental understanding is vital to enable rational design of high performance emitters, and in turn unlock the potential of upconversion in applications across photovoltaics and light emitting diodes. Time-resolved and steady-state fluorescence emission spectroscopy was used to compare the performance of a standard upconversion system to one with a deuterated emitter. For perylene, deuteration was found to decrease the rate constant for first order nonradiative losses by 16 %, while leaving other electronic and kinetic parameters unchanged. This selective control over one of the emitter properties allowed for straightforward and direct comparison between the systems, and resulted in a 45% increase in upconverter performance under low intensity excitation. Transient absorption spectroscopy was used to characterise a range of commonly used emitter species. The family of emitters investigated were found to be largely similar in their decay kinetics, indicating that any comparative advantage comes about primarily through different intrinsic efficiencies of the annihilation step. A system with two emitter species was also studied, and its superior performance attributed to an improved rate of exciton transport, rather than annihilation events between heterogeneous emitter pairs. Finally, magnetic field effects and resonance spectroscopy were pursued as ways to probe the nature of spin mixing in the annihilation event. Fibre based experimental platforms were developed to enable these techniques for air sensitive solutions, although resonance signal remained elusive. Nonetheless, modelling the effects of static magnetic fields on upconversion emission reveals the critical importance of emitter pair orientation as the spins interact. In the absence of external magnetic fields, this orientation factor is identified as the key determinant of the annihilation outcome, rather than the individual spin states of the interacting triplets as was previously thought. en_US
dc.language English
dc.language.iso EN en_US
dc.publisher UNSW, Sydney en_US
dc.rights CC BY-NC-ND 3.0 en_US
dc.rights.uri en_US
dc.subject.other Annihilation en_US
dc.subject.other Triplet-triplet annihilation en_US
dc.subject.other Photochemical upconversion en_US
dc.subject.other Spin en_US
dc.title The role of spin in triplet-triplet annihilation upconversion en_US
dc.type Thesis en_US
dcterms.accessRights open access
dcterms.rightsHolder Danos, Andrew
dspace.entity.type Publication en_US
unsw.accessRights.uri 2022-03-02 en_US
unsw.description.embargoNote Embargoed until 2022-03-02
unsw.relation.faculty Science
unsw.relation.originalPublicationAffiliation Danos, Andrew, Chemistry, Faculty of Science, UNSW en_US
unsw.relation.originalPublicationAffiliation Timothy, Schmidt, Chemistry, Faculty of Science, UNSW en_US
unsw.relation.originalPublicationAffiliation Dane, McCamey, Physics, Faculty of Science, UNSW en_US School of Chemistry *
unsw.thesis.degreetype PhD Doctorate en_US
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