| 1. |
- Börjesson, Karl, 1982, et al.
(författare)
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Conjugated anthracene dendrimers with monomer-like fluorescence
- 2014
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 4:38, s. 19846-19850
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Tidskriftsartikel (refereegranskat)abstract
- Two generations of highly emissive conjugated anthracene dendrimers containing up to 9 anthracene units are presented. In these dendrimers, anthracene-like absorption and emission properties are preserved due to the relatively weak electronic coupling between the anthracene units, while evidence of fast crosstalk within the molecular framework is still observed.
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| 2. |
- Börjesson, Karl, 1982, et al.
(författare)
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Photon up-conversion and molecular solar thermal energy storage: New materials and devices
- 2014
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Ingår i: 2014 IEEE Photonics Conference, IPC 2014. ; , s. 445-446
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Konferensbidrag (refereegranskat)abstract
- In a future society with limited access to fossil fuels, technologies for efficient on demand delivery of renewable energy are highly desirable. In this regard, methods that allow for solar energy storage and on demand solar driven energy generation are particularly relevant since the sun is the most abundant energy source.
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| 3. |
- Börjesson, Karl, 1982, et al.
(författare)
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Photon up-converting devices for solar fuels
- 2014
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Ingår i: SPIE Newsroom. - : SPIE-Intl Soc Optical Eng. - 1818-2259.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Employing a molecular solution capable of triplet-triplet annihilation in a layered microfluidic device enables the solar spectrum to be locally modified toward the UV, increasing solar energy system efficiency.
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| 4. |
- Börjesson, Karl, 1982, et al.
(författare)
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Photon upconversion facilitated molecular solar energy storage
- 2013
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Ingår i: Journal of Materials Chemistry. - 1364-5501 .- 0959-9428. ; 1, s. 8521-8524
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Tidskriftsartikel (refereegranskat)abstract
- Photon upconversion is used to facilitate the production of a solar fuel. This is done by collocating a triplet–triplet annihilation upconversion system in a microfluidic device with a molecular solar thermal energy storage system. Incoherent truncated white light is used to drive the reaction and the green part of the spectrum is upconverted to blue light, which in turn is absorbed by the solar fuel.
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| 5. |
- Dzebo, Damir, 1986, et al.
(författare)
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Intramolecular Triplet-Triplet Annihilation Upconversion in 9,10-Diphenylanthracene Oligomers and Dendrimers
- 2016
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 120:41, s. 23397-23406
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Tidskriftsartikel (refereegranskat)abstract
- An important challenge when developing materials for triplet triplet annihilation upconversion (TTA-UC) is achieving efficient and well-functioning solid-state systems. We here explore the effect of intramolecular TTA in oligomers and dendrimers based on the 9,10-diphenylanthracene (DPA) chromophore. The macromolecules are sensitized using palladium porphyrin, both in solution and in solid poly(methyl methacrylate) (PMMA), demonstrating a positive effect on overall upconversion in the solid state correlating with the well-controlled size of the DPA constructs. The UC kinetics is modeled and fit to steady-state and time-resolved emission data to give further insight into the intramolecular excited-state migration and annihilation in the macromolecular annihilator systems.
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| 6. |
- Dzebo, Damir, 1986
(författare)
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Photon Upconversion through Triplet-Triplet Annihilation: Towards Higher Efficiency and Solid State Applications
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The sun is the only renewable energy source that can accommodate humanity’s energyneeds today and in the foreseeable future. The sunlight reaching the planet’s surfaceis filtrated through the atmosphere, reducing its UV-light intensity in the 300-400 nmrange, which indeed can be harmful to life as we know it in too large doses. However,many useful photoreactions require in practice such high-energy UV-photons, like thecatalytic splitting of water to oxygen and hydrogen gas or molecular in-bond energystorage through isomerization to produce heat when reverting to the initial state. Theefficiency of these applications could be improved with efficient conversion of low-energyvisible to high-energy UV-light.One way to achieve this type of photon upconversion (UC) is through the process calledTriplet-Triplet Annihilation (TTA) relying on the interaction between two molecules; asensitizer and an annihilator. The sensitizer absorbs low energy visible photons as inputand transfers that energy through Triplet Energy Transfer (TET) to an annihilator. Twotriplet-excited annihilators can thereafter perform TTA, merging the energy equivalentsof the two low-energy photons to produce one high-energy photon as output.This Thesis is focused on improving the known bimolecular UC system in fluidenvironment and approaching the ultimate goal of high efficiency UC in solid materials. Inthe fluid system I demonstrate the employment of thiol- and thioether-based compoundsas scavengers for singlet excited oxygen with positive effect on UC efficiency and stability.In an attempt to aid future design and optimization of upconversion system componentsthe anthracene is 9,10-substituted with electron withdrawing or donating groups whileits TTA-UC function is evaluated revealing that substitution at para-positions leadsto least perturbation of its spectroscopic properties. The ultimate goal is to achievesupramolecular TTA-UC systems capable of efficient intra-molecular TET and TTAprocesses and unhindered emission of the upconverted photons. As a first step, we focuson the intra-molecular TTA process with oligomers and dendrimers of 9,10-diphenylanthracene (DPA) which display positive effects on UC efficiency in solid matrix. Inthe second step the focus is on the intra-molecular TET process where the sensitizer-annihilator complexes are explored through Lewis base-acid coupling with orthogonaltransition moments for minimum excited state short circuit effect. Additionally, kineticsimulations of the TTA-UC processes are conducted to aid understanding and optimization.Finally, one TTA-UC system is also applied to chemical in-bond energy storage.
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| 7. |
- Dzebo, Damir, 1986, et al.
(författare)
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Robust triplet-triplet annihilation photon upconversion by efficient oxygen scavenging
- 2017
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Ingår i: Photochemical and Photobiological Sciences. - : Springer Science and Business Media LLC. - 1474-9092 .- 1474-905X. ; 16:8, s. 1327-1334
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Tidskriftsartikel (refereegranskat)abstract
- We hereby present a simple method for reducing the effect of oxygen quenching in Triplet-Triplet Annihilation Upconversion (TTA-UC) systems. A number of commercially available thioethers and one thiol have been tested as singlet oxygen scavengers. Recording of the upconverted emission from a well-studied PdOEP (sensitizer)-DPA (annihilator/emitter) couple has been made over time with steady-state excitation capturing the steady-state kinetics of the TTA-UC process as the solubilized oxygen is depleted by reaction with the scavengers. The efficiency of the TTA-UC process is compared between chemical oxygen scavenging and mechanical removal by inert gas purging or the freeze-pump-thaw method. Selected methods are combined to explore the highest attainable TTA-UC quantum yield. A maximum TTA-UC quantum yield of 21% with the shortest UC onset time was obtained with dimethylthiomethane (DMTM) as the scavenger in an air-saturated solvent and slightly higher quantum yields were obtained in combination with other deoxygenation techniques. Samples containing DMTM displayed little decrease in the quantum yield over four hours of continuous high intensity irradiation, which illustrates the robustness of applying chemical oxygen removal in TTA-UC instead of more time-consuming mechanical processes that usually require specialized equipment.
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| 8. |
- Gray, Victor, 1988, et al.
(författare)
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Photophysical characterization of the 9,10-disubstituted anthracene chromophore and its applications in triplet-triplet annihilation photon upconversion
- 2015
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Ingår i: Journal of Materials Chemistry C. - : Royal Society of Chemistry (RSC). - 2050-7526 .- 2050-7534. ; 3:42, s. 11111-11121
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Tidskriftsartikel (refereegranskat)abstract
- Molecules based on anthracene are commonly used in applications such as OLEDs and triplet-triplet annihilation upconversion. In future design of blue emitting materials it is useful to know which part of the molecule can be altered in order to obtain new physical properties without losing the inherent optical properties. We have studied the effect of substitution of 9,10-substituted anthracenes. Eight anthracenes with aromatic phenyl and thiophene substituents were synthesised, containing both electron donating and accepting groups. The substitutions were found to affect the UV/Vis absorption only to a small extent, however the fluorescence properties were more affected with the thiophene substituents that decreased the fluorescence quantum yield from unity to
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| 9. |
- Gray, Victor, 1988, et al.
(författare)
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Porphyrin-Anthracene Complexes: Potential in Triplet-Triplet Annihilation Upconversion
- 2016
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 120:34, s. 19018-19026
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Tidskriftsartikel (refereegranskat)abstract
- Triplet-triplet annihilation photon upconversion (TTA-UC) systems contain both an absorbing and an emitting molecule, the sensitizer and annihilator, respectively. Through a series of energy-transfer steps, two low frequency,photons can be combined into one high frequency photon. In organic solvents, the required energy transfer steps are limited by diffusion and are relatively efficient. In solid-state systems, however, the diffusion is slower, which usually results in lower efficiencies for these systems. An interesting way around this is to connect the sensitizer and annihilator. In order to increase understanding of the TTA-UC process in supramolecular systems, we synthesized four pyridine-substituted anthracene annihilators capable of coordinating axially to a zinc octaethylporphyrin sensitizer with a maximum binding constant of 6000 M-1 in toluene. This is a first example of a sensitizer-annihilator coordination complex for TTA-UC. Both the upconversion efficiency and the parasitic quenching of excited annihilator singlets by the sensitizer through Forster resonant energy transfer (FRET) were studied. On the basis of the findings herein, possible strategies for future supramolecular TTA systems with minimized FRET quenching are discussed.
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| 10. |
- Gray, Victor, 1988, et al.
(författare)
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Triplet-triplet annihilation photon-upconversion: Towards solar energy applications
- 2014
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 16:22, s. 10345-10352
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Forskningsöversikt (refereegranskat)abstract
- Solar power production and solar energy storage are important research areas for development of technologies that can facilitate a transition to a future society independent of fossil fuel based energy sources. Devices for direct conversion of solar photons suffer from poor efficiencies due to spectrum losses, which are caused by energy mismatch between the optical absorption of the devices and the broadband irradiation provided by the sun. In this context, photon-upconversion technologies are becoming increasingly interesting since they might offer an efficient way of converting low energy solar energy photons into higher energy photons, ideal for solar power production and solar energy storage. This perspective discusses recent progress in triplet-triplet annihilation (TTA) photon-upconversion systems and devices for solar energy applications. Furthermore, challenges with evaluation of the efficiency of TTA-photon-upconversion systems are discussed and a general approach for evaluation and comparison of existing systems is suggested.
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