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 42 for “"triplet excitons"”.
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Spin-sensitive probes of triplet excitons in organic semiconductors
… investigates the spin interactions of spin-1 triplet excitons formed by singlet fission. Singlet fission produces two triplet excitons from one light-induced singlet state and holds promise to enable solar energy generation beyond traditional efficiency limits. As the lifetime of triplet pairs …
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Controlling Triplet Excitons in Organic Semiconductors with Lanthanide-Doped Nanoparticles
… absorption, emission, and charge generation. Triplet excitons play a central role in determining the excited-state dynamics of OSCs under both optical and electrical excitation. However, in most closed-shell OSCs, triplet excitons are dark states that can neither be directly photogenerated nor …
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Science and Engineering of Spin Triplet Excitons in Luminescent Molecular Semiconductors
… from OLEDs requires careful management of spin-triplet excitons, which are typically non-emissive. For successful management, the formation and harvesting dynamics of triplet excitons must be probed directly. In this thesis, we employ optical and spin-sensitive probes to reveal the dynamics of …
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Triplet Excitons in Natural Photosynthetic and Artificial Light Harvesting Systems: Measurement and Modeling.
… oxygen (1O2) by energy transfer from the (B)Chl triplet state (3(B)Chl) to the oxygen ground state. Natural photosynthetic systems must protect themselves from 1O2, typically done by positioning carotenoids within a few angstroms of each (B)Chl molecule to quench 3(B)Chl states. Using …
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Interfacial engineering and spectroscopy of spin-triplet excitons for singlet fission sensitization of silicon solar cells
… shown any evidence for energy transfer of spin-triplet excitons (the product states of singlet fission) to silicon. The challenge derives from the quantum mechanical spin properties of triplet excitons, resulting in triplets having vanishingly low ability to emit light, low mobility and small …
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Triplet Exciton Management via Solid-State Interactions in Organic Semiconductors
Tightly-bound excitons play an important role in the function of molecular materials for light emission and light harvesting. This thesis investigates the effects of solid-state interactions on triplet excitons in a new family of organometallic light emitters, carbene-metal-amides (CMAs). Triplet …
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Spectroscopic Study of Triplet Exciton Dynamics at the Hybrid Organic-Inorganic Interface
The control and utilisation of spin-triplet excitons in organic semiconductors is highly sought after for the next generation of Optoelectronic applications. Of particular interest is the utilisation of these photoexcited states in the singlet-fission photon-multiplier and triplet-triplet …
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Triplet exciton dynamics in conjugated polymer films
… for 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 …
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Singlet exciton fission : applications to solar energy harvesting
… requires energy transfer from the non-emissive triplet exciton to the semiconducting material, a process which has not been demonstrated. I prove that colloidal nanocrystals accept triplet excitons from the singlet fission molecule tetracene. This enables future devices where the combine singlet …
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Electrical and magnetic properties of organic semiconductors: Electrical conductivity and electron spin resonance studies of semiconducting, organic, charge transfer salts.
… The ESR spectra of these salts are attributed to triplet excitons showing that the spin-spin and electronelectron correlation effects are important. In the ESR spectra (Chapter III) of some TCNQ salts dipolar splitting is observed confirming the spin-spin interaction. These triplet excitons are …
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Exciton and Energy Transfer Dynamics in Hybrid Perovskite and Lanthanide Nanomaterials
… oxygen, and heat. In organic semiconductors, triplet excitons are of great importance because they are usually the lowest-energy states and they show long lifetimes and diffusion lengths. However, triplet excitons are dark states. This makes harvesting triplet energy for optoelectronic …
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Removing the Spin-Triplet Loss Pathway in Organic Solar Cells: A Strategy to Enhance Radiative Efficiency and Minimise Energy Loss
… our work into suppressing the formation of triplet excitons in organic solar cells, 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 …
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Singlet exciton fission-enhanced silicon photovoltaics: Interfacial engineering, device design and spectroscopic technique development
… the high energy light and transferring the triplet excitons generated from the singlet fission process to silicon, the photocurrent in this spectral region can be doubled, with the potential of raising the efficiency from the traditional limit of 29.4 % to up to 42 %. The greatest challenge …
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Charge recombination in organic small-molecule solar cells by Jiye Lee.
… (PTCBI). We report the formation of triplet excitons on PTCBI molecules, which may be an important source of recombination loss in CuPC/PTCBI photovoltaic cells. Second, spin-forbidden transition can be employed to reduce the recombination loss in organic solar cells. We show with a …
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Quantum efficiency and fission rate in tetracene
… than the Shockley-Queisser limit due to two excitons produced with one incident photon. In a singlet fission material, an absorbed photon excites a singlet exciton and then split into two triplet excitons with energy around half of the singlet exciton. Tetracene is a potential candidate for …
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Efficient Organic Light-emitting Diodes with Singlet, Triplet and Doublet Excitons
… research progress recently. Tightly-bound excitons play an important role in the function of energy conversion and light emission for OLEDs. Many properties of excitons are determined by the spin state including singlets, triplets and doublets. Triplet excitons are regarded as dark states …
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Design of Singlet Fission Chromophores through the Introduction of N-Oxyl Fragments.
… singlet exciton splits to two long-lived triplet excitons. Generating a larger number of longer-lived excitons, singlet fission has the potential to enhance the photoelectric conversion efficiency. The exploitation of this phenomenon in the photovoltaic industry is however impacted by the …
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Reducing recombination in organic photovoltaics
… energy level cascades and promotion of triplet state excitons. The former relies on a thin layer of material placed between the active layers of a photovoltaic device to destabilize excitons. If the interfacial material is chosen properly, it can significantly improve device performance. …
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Overcoming Efficiency Limits in Photovoltaic Devices
… an excited singlet exciton splits to form two triplet excitons on neighbouring molecules. The process in organics is referred to as singlet fission. Producing a device that can make use of the singlet fission process however, has proved difficult, limited in part by the instability of singlet …
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Field Induced Polymer Electroluminescence
… emissive system to harvest both singlet and triplet excitons. Various polymer dielectric materials are studied to optimize the electric field on the emitting layers. Multiple organic materials are considered as charge generating layers including polymers, molecular dopants, and carbon …
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