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Showing 1 to 20 of 23 for “"Exciton diffusion"”.
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Design and construction of instruments for exciton diffusion characterization and for patterning of thin films
… devices. One instrument characterizes exciton diffusion and the other patterns organic thin films. Exciton diffusion characteristics are important to study in organic materials because excitons mediate the transport of energy. In this work, a fluorescence microscope is designed and …
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Organic solar cells based on liquid crystalline and polycrystalline thin films
… cells. Maximum efficiencies estimated based on excitonic character of organic solar cells show power conversion efficiencies larger than 10% are possible in principle. However, their performance is often limited due to small exciton diffusion lengths and poor transport properties which may be …
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Excitonics for Organic Electronics
… are tightly bound electron-hole pairs known as excitons. Here, the link between OLED excitonics and operational stability is studied in active OLEDs. First, the exciton distribution is investigated in active OLEDs with doped and undoped emissive layers. In both types of OLEDs, a surprisingly …
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Organic photovoltaics and concentrators
… devices limited in performance by the exciton diffusion bottleneck. This unique architecture is analyzed for its functionality and the efficiencies of each added step is quantified. Although the introduction of additional energy transduction will ultimately introduce more losses, …
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Fluorescence Enhancement Strategies for Polymer Semiconductors
… the solid-state fluorescence quantum yield, exciton lifetime and exciton diffusion length significantly in comparison to that without phenyl-addition. 2. Energy transfer to a highly fluorescent chromophore It is shown that for the high mobility polymer …
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Photosynthesis-inspired device architectures for organic photovoltaics
… (1) a trade-off between light absorption and exciton diffusion 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 …
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Nonequilibrium energy transport in heterogeneous nanoscale semiconductors
… optoelectronic properties with emphasis on excitons. At first, continuum-level analytical theories and finite element simulations are employed to derive exciton distributions in semiconductor films. These models are applied to transient photoluminescence interfacial quenching experiments of …
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Photoluminescence quenching of organic thin films by transparent conductive oxides
… model and a Monte Carlo simulation for exciton dynamics in amorphous organic solids, we find that the exciton diffusion length in bulk Alq3 is in the range of 70--80 A. We also find that for SnO2 films deposited without oxygen in the sputtering ambient, resonant energy transfer from Alq3 …
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Sensitized energy transfer for organic solar cells, optical solar concentrators, and solar pumped lasers
The separation of chromophore absorption and excitonic processes, such as singlet exciton fission and photoluminescence, offers several advantages to the design of organic solar cells and luminescent solar concentrators (LSCs) for the end goal of achieving a lower cost solar energy generation. This …
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Surface plasmon polariton mediated energy transfer from external antennas into organic photovoltaic cells
… the device thickness leads to a decrease in exciton diffusion efficiency and vice versa. In this thesis, I demonstrate organic solar cells with an external light absorbing antenna. Light is absorbed by the external antenna and subsequently transferred into the photovoltaic cell via surface …
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Applications of nanoimprinted structures to organic photovoltaics
… decouples the light propagation from the exciton diffusion path. This is an optimized situation for efficient charge transfer. Enhanced power absorption into the OPV active layer has been demonstrated via numerical computation methods, including COMSOL FEM and Lumerical FDTD. The challenge …
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Optical spectroscopy of conjugated polymers.
… to model the behaviour of the photogenerated exciton after excitation. At the same time, the . probing sheds light on the mechanisms at work in the deceleration of the implanted ions and the nature and location of the damage produced. A study of the effect of applied electrical field on the …
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Nano-structured materials for optoelectronic devices
… relationships in these devices. Short exciton diffusion length limits the efficiency of most exciton-based solar cells. By introducing nano-structured architectures to solar cells, excitons can be separated more effectively, leading to an enhancement of the cell’s power conversion …
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Auger-mediated processes and photoluminescence in group iv semiconductor nanostructures
… the nanostructure, and a severe reduction of the exciton diffusion length. For the SOI system, an apparently successful competition of the radiative recombination of carriers in a condensed excitonic phase with Auger processes is observed. The influence of the Si/SiO_2 interface on the …
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Theoretical investigations of the electronic processes in organic photovoltaics
… we get an accurate prediction of triplet diffusion and show that only a small decrease occurs when the crystal becomes highly disordered, and no significant traps exist. Our models of the organic/organic interface reveals that the the simple picture of constant HOMO and LUMO levels …
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An analysis of exciton transport, electron tunneling, and electromigration in nanotube and nanowire systems
… operation from the light absorption and exciton transport behaviors of single and aggregate nanotubes. To do so, we treated single nanotube properties as random variables, describing the nanotube network as distributions of those properties. Applying the model to different solar cell …
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Engineering the optical properties of luminescent solar concentrators at the molecular scale
… and optical waveguiding to triplet exciton transport in crystalline tetracene (Tc) and rubrene (Rb). A timeresolved imaging technique that maps the triplet distribution showed that optical waveguiding dominates over diffusion and can transport energy several micrometers at the high …
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Interfacing spin-based quantum sensors with complex systems
… 3, nanodiamonds are used to study triplet exciton diffusion in an organic semiconductor material. In this experiment, NV relaxometry is used to probe the diffusion process of optically generated triplet excitons. It was observed that the longitudinal relaxation time of NV (T1) is related to …
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Interactions of Organic Fluorophores with Plasmonic Surface Lattice Resonances
… of Mie-scattering dielectric particles or excitonic nanoparticles.</p> <p>SLRs are another plasmonic mode, in addition to surface plasmons polaritons and LSPRs, through which visible light can be absorbed or scattered. In addition, SLRs in combination with various excitonic materials have …
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Chain-Growth Polymerization of 3-Hexylthiophene Towards Well-Defined Semiconductor Block Copolymers
… observed with domain sizes in the range of the exciton diffusion length. In conclusion, the optimization of the synthesis of P3HT allowed a better understanding of fundamental aspects about its molecular weight dependent structures and the resulting properties. Further, new end groups could be …
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