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 14 of 14 for “"charge-transfer state"”.
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Ultrafast Spectroscopy of Organic Semiconductors: Singlet Fission and Nonfullerene Acceptors for Organic Photovoltaics
… direct coupling between the singlet and triplet states, and another model involves an intermediate charge transfer state. Transient absorption spectroscopy allowed us to examine singlet fission in films of pentacene, fluorinated pentacene, and coevaporated blends of various mixing ratios. We …
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Removing the Spin-Triplet Loss Pathway in Organic Solar Cells: A Strategy to Enhance Radiative Efficiency and Minimise Energy Loss
… created as a result of unavoidable non-geminate charge recombination processes. Triplet excitons represent a major non-radiative loss pathway in organic solar cells and through this work, we demonstrate tactics to reduce the non-radiative decay of photo-generated charges and thereby enhance the …
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Photosynthesis-inspired device architectures for organic photovoltaics
… and (2) low open-circuit voltage due to charge recombination at the donor-acceptor interface. In this work, we demonstrate two new device architectures inspired by photosynthesis that aim to overcome these two challenges. First, we overcome the trade-off between light absorption and …
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Ultrafast Charge and Energy transfer Dynamics in Organic-Transition Metal Dichalcogenides Heterostructures
… devices. Afterwards the ultrafast energy, charge transfer and spin-valley physics of Organic-TMD Heterostructures, namely Pentacene/MoTe2 and Pentacene/WSe2 were examined. It was found that excitation at the electronic gap of MoTe2 leads to a Type II to type I band alignment cross over in …
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Photophysics of Hybrid Perovskites with Electroactive Molecules
… cations actively participate in excited-state processes through inorganic–organic coupling. Central to this exploration is how structural parameters, such as linker length, molecular orientation, and dimensionality, dictate the nature and strength of this hybrid coupling. Photoinduced …
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The Development of 2,3-Diarylindenes as Integrated Fluorescent Estrogens
… group produced a quasi-planar intramolecular charge transfer state, with emission from 490 nm in heptane to 672 nm in acetonitrile. In the m-position, a nitro group produces a twisted intramolecular charge transfer (TICT) state with emission up to 690 nm in chloroform. A nitro group in the …
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Ultrafast electron dynamics in Fe(CO)5 and Cr(CO)6
… gives access only to the final ionic states. Corresponding calculations to simulate these spectra are still in development. The peak energies and their evolution in time with respect to the initiation pump pulse have been determined, these peaks have been assigned based on literature …
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Spectroscopic study of charge-separation dynamics in [pi]-conjugated systems
… we investigate the dynamics of excited states involved in the operation of organic photovoltaic devices. Using spectroscopic and numerical tools, we study the photophysical properties of push-pull polymers, donoracceptor interfaces, and solution-processed small-molecule organic …
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Chemically Modified Titanium-Oxo Clusters as Molecular Materials
… into the visible region up to 475 nm. An energy transfer mechanism involving the salicylate-to-Ti4+ charge-transfer state is proposed to account for the largely red-shifted excitation wavelengths, which is supported by both steady-state and time-resolved photoluminescence spectroscopic data.
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Ultrafast extreme ultraviolet spectroscopy of transition metal dithiolate coordination complexes
… for the identification of a ligand-to-metal charge transfer (LMCT) excited state whose spin can be determined by comparison to semi-empirical ligand field multiplet calculations. The combination of optical and x-ray techniques is crucial to identifying relaxation processes that affect …
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Triplet Exciton Management in Organic Electronic Devices
… 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 both organic light-emitting …
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Excitonic spin engineering in optoelectronic devices
… the normal OPV functions such as absorption and charge transport with a small interfacial layer of a fission material. With the efficiency of singlet fission established, we then demonstrate how it can be utilized by building an optical downconverter with tetracene as the fission material and PbS …
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Ultrafast Spectroscopic Studies of Solution-Processing Organic Photovoltaic Materials and Devices
… the conversion efficiency from molecular excited states into charge carriers. Chapter 2 presents a historical review of different material combination, device architecture and key processes relevant for solar cell performance. This leads to the key questions that this thesis addresses: which …
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Generation, recombination and extraction of charges in polymer
… organic materials systems, the yield of charge generation can be very efficient. However, a detailed understanding of the free charge carrier generation mechanisms at the donor acceptor interface and the energy loss associated with it needs to be established. Moreover, organic solar cells …