Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 388 for “"Exciton"”.
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On exciton-vibration and exciton-photon interactions in organic semiconductors
… is dominated by bound electron-hole pairs called excitons, which are often strongly affected by hundreds of possible molecular vibrations. Although quantum theory contains all the ingredients to describe these complex phenomena, in practice it is only possible to solve the corresponding equations …
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Data-driven approach to understanding exciton-exciton interactions in CsPbBr₃ nanocrystals
… nanocrystals relies on emission from biexciton or doubly excited states. Knowledge of the spectral properties of biexciton states is critical for understanding optical gain development as well as many-body interactions between charge carriers more broadly. In this thesis, we develop and …
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Exciton-polaritons in thermal equilibrium : from Bose-Einstein condensation to exciton-polaritonics
… collective system, namely, microcavity exciton-polariton Bose-Einstein condensates. Microcavity exciton-polaritons, hereafter simply polaritons, are bosonic quasiparticles formed in a resonant semiconductor microcavity by coupling the excitonic polarizabilities in quantum wells to the …
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Singlet exciton fission, a multi-exciton generation process, in organic semiconductor solar cells
… work we explore implementations of a multiple exciton generation process, singlet exciton fission, to work around the Shockley-Queisser limit, according to which, all single junctions cells have a theoretical efficiency limit of 33.7%. This is the first implementation of a singlet fission …
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Exciton Dynamics in DNA-Chromophore Assemblies
Excitonic systems have the potential to provide new materials for light harvesting, computing, and imaging. Such applications require control over the spatiotemporal evolution of excited states. Natural light harvesting systems achieve the required control through precise molecular placement; …
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Simulating exciton dynamics in organic semiconductors
… organic semiconductors: the transport of Frenkel exciton and dissociation of charge-transfer (CT) exciton. Frenkel excitons are tightly bound electron-hole pairs created upon photo-excitation of molecules and they carry the excess energy imparted by photons.
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Correlated exciton dynamics in semiconductor nanostructures
… fundamentally important electronic state is an exciton, an excited electron bound to a positively charged vacancy. Excitons can become correlated with other excitons, mutually influencing one another and exhibiting collective properties. The focus of this dissertation concerns the origins, …
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Fluctuations and exciton dynamics in molecular semiconductors
… structure of molecular semiconductors and of the exciton dynamics in the same materials. The method employed in this thesis is time- and angle-resolved photoemission spectroscopy. In the first part, the electronic structure of molecular semiconductors at equilibrium is considered. We show that the …
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Exciton behaviour at organic solar cell interfaces
… donor-acceptor interfacial surface area where excitons are split apart to create free charges. The generation of free charges after photo-excitation is a main factor influencing solar cell efficiency. However, the mechanisms of charge transfer and the competing process of charge recombination …
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Triplet exciton dynamics in conjugated polymer films
… efficient use of these novel materials. Triplet excitons are believed to play an important role in conjugated polymer-based device operation. Triplet excitons are also believed to play a primary role in photo-oxidative degredation of polymer devices. Two-photon photoemission is used to probe …
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Nonlinear Processes in Room Temperature Exciton-Polaritons
… where hybrid light-matter states known as exciton-polaritons form, leading to enhanced light matter interaction, modified material properties, and novel quantum phenomena. In this thesis, we explore the phenomenology of exciton-polaritons in strained TMD microcavities, 2D perovskites, …
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Studies of exciton interactions in molecular aggregates
211 leaves : ill., tables, graphs ; 30 cm.
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Triplet Exciton Management in Organic Electronic Devices
… diodes and organic photovoltaics. Tightly-bound excitons form intermediate states in the operation of both organic light-emitting diodes and organic photovoltaics. Many properties of an exciton are determined by its spin state, which can either be a spin-zero singlet or a spin-one triplet. In …
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Engineering J-aggregate cavity exciton-polariton devices
… creating light-matter quasi-particles known as exciton-polaritons, even at room temperature. In this thesis, I discuss my research on the properties of J-aggregate thin films and on advancing the device and materials engineering of strongly-coupled devices based on J-aggregate thin films to the …
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Probing Exciton Dynamics in Metal–Organic Frameworks
Bound electron–hole pairs, known as excitons, are key carriers of energy during a material’s interaction with light. Therefore extending understanding and control over exciton dynamics can potentially break the bottlenecks that currently limit solar energy harvesting technologies. However, design …
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Exciton Dynamics in Perovskite CsPbBr₃ Semiconductor Nanocrystals
… different edge lengths (L = 4.9 - 13.2 nm). The excitonic transitions observed in the absorption spectra can be explained with an effective mass model considering the quasicubic NC shape and non-parabolicity of the electronic bands. We observe a temperature-dependent Stokes shift; while the trend …
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Control of Exciton Photon Coupling in Nano-structures
<p>In this thesis, we study the interaction of excitons with photons and plasmons and methods to control and enhance this interaction. This study is categorized in three parts: light-matter interaction in microcavity structures, direct dipole-dipole interactions, and plasmon-exciton interaction in …
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Singlet exciton fission : applications to solar energy harvesting
Singlet exciton fission transforms a single molecular excited state into two excited states of half the energy. When used in solar cells it can double the photocurrent from high energy photons increasing the maximum theoretical power efficiency to greater than 40%. The steady state singlet fission …
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Theoretical Design of Molecular Nanostructures for Exciton Control
… harness control of delocalized excitations, or excitons, via programmed molecular structures. The dynamics of these excitons enable energy and information transfer within molecular networks, positioning chromophore assemblies as ideal candidates for a number of technologies such as solar energy …
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Exciton Dynamics in Organic and Inorganic Nanoscale Materials
… I investigate the dynamics of optically excited excitons in these materials and the available pathways for their recombination. I first study the interaction between excitons and the supramolecular lattice found in nanotubular molecular aggregates. The mechanism of photobrightening in these …
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