| 1. |
- Mahajan, Anubha, et al.
(author)
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Fine-mapping type 2 diabetes loci to single-variant resolution using high-density imputation and islet-specific epigenome maps
- 2018
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In: Nature Genetics. - : NATURE PUBLISHING GROUP. - 1061-4036 .- 1546-1718. ; 50:11, s. 1505-
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Journal article (peer-reviewed)abstract
- We expanded GWAS discovery for type 2 diabetes (T2D) by combining data from 898,130 European-descent individuals (9% cases), after imputation to high-density reference panels. With these data, we (i) extend the inventory of T2D-risk variants (243 loci,135 newly implicated in T2D predisposition, comprising 403 distinct association signals); (ii) enrich discovery of lower-frequency risk alleles (80 index variants with minor allele frequency <5%,14 with estimated allelic odds ratio >2); (iii) substantially improve fine-mapping of causal variants (at 51 signals, one variant accounted for >80% posterior probability of association (PPA)); (iv) extend fine-mapping through integration of tissue-specific epigenomic information (islet regulatory annotations extend the number of variants with PPA >80% to 73); (v) highlight validated therapeutic targets (18 genes with associations attributable to coding variants); and (vi) demonstrate enhanced potential for clinical translation (genome-wide chip heritability explains 18% of T2D risk; individuals in the extremes of a T2D polygenic risk score differ more than ninefold in prevalence).
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| 2. |
- Toolan, Daniel T. W., et al.
(author)
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Insights into the Structure and Self-Assembly of Organic-Semiconductor/Quantum-Dot Blends
- 2022
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In: Advanced Functional Materials. - : John Wiley & Sons. - 1616-301X .- 1616-3028. ; 32:13
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Journal article (peer-reviewed)abstract
- Controlling the dispersibility of crystalline inorganic quantum dots (QD) within organic-QD nanocomposite films is critical for a wide range of optoelectronic devices. A promising way to control nanoscale structure in these nanocomposites is via the use of appropriate organic ligands on the QD, which help to compatibilize them with the organic host, both electronically and structurally. Here, using combined small-angle X-ray and neutron scattering, the authors demonstrate and quantify the incorporation of such a compatibilizing, electronically active, organic semiconductor ligand species into the native oleic acid ligand envelope of lead sulphide, QDs, and how this ligand loading may be easily controlled. Further more, in situ grazing incidence wide/small angle X-ray scattering demonstrate how QD ligand surface chemistry has a pronounced effect on the self-assembly of the nanocomposite film in terms of both small-molecule crystallization and QD dispersion versus ordering/aggregation. The approach demonstrated here shows the important role which the degree of incorporation of an active ligand, closely related in chemical structure to the host small-molecule organic matrix, plays in both the self-assembly of the QD and small-molecule components and in determining the final optoelectronic properties of the system.
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| 3. |
- Toolan, Daniel T. W., et al.
(author)
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Linking microscale morphologies to localised performance in singlet fission quantum dot photon multiplier thin films
- 2022
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In: Journal of Materials Chemistry C. - : Royal Society of Chemistry. - 2050-7526 .- 2050-7534. ; 10:31, s. 11192-11198
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Journal article (peer-reviewed)abstract
- Hybrid small-molecule/quantum dot films have the potential to reduce thermalization losses in single-junction photovoltaics as photon multiplication devices. Here grazing incidence X-ray scattering, optical microscopy and IR fluorescence microscopy (probing materials at two distinct wavelengths), provide new insight into highly complex morphologies across nm and mu m lengthscales to provide direct links between morphologies and photon multiplication performance. Results show that within the small molecule crystallites three different QD morphologies may be identified; (i) large quantum dot aggregates at the crystallite nucleus, (ii) relatively well-dispersed quantum dots and (iii) as aggregated quantum dots "swept" from the growing crystallite and that regions containing aggregate quantum dot features lead to relatively poor photon multiplication performance. These results establish how combinations of scattering and microscopy may be employed to reveal new insights into the structure and function of small molecule:quantum dot blends.
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| 4. |
- Allardice, Jesse R., et al.
(author)
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Engineering Molecular Ligand Shells on Quantum Dots for Quantitative Harvesting of Triplet Excitons Generated by Singlet Fission
- 2019
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In: Journal of the American Chemical Society. - : AMER CHEMICAL SOC. - 0002-7863 .- 1520-5126. ; 141:32, s. 12907-12915
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Journal article (peer-reviewed)abstract
- Singlet fission is an exciton multiplication process in organic molecules in which a photogenerated spin-singlet exciton is rapidly and efficiently converted to two spin-triplet excitons. This process offers a mechanism to break the Shockley-Queisser limit by overcoming the thermalization losses inherent to all single-junction photovoltaics. One of the most promising methods to harness the singlet fission process is via the efficient extraction of the dark triplet excitons into quantum dots (QDs) where they can recombine radiatively, thereby converting high-energy photons to pairs of low-energy photons, which can then be captured in traditional inorganic PVs such as Si. Such a singlet fission photon multiplication (SF-PM) process could increase the efficiency of the best Si cells from 26.7% to 32.5%, breaking the Shockley-Queisser limit. However, there has been no demonstration of such a singlet fission photon multiplication (SF-PM) process in a bulk system to date. Here, we demonstrate a solution-based bulk SF-PM system based on the singlet fission material TIPS-Tc combined with PbS QDs. Using a range of steady-state and time-resolved measurements combined with analytical modeling we study the dynamics and mechanism of the triplet harvesting process. We show that the system absorbs >95% of incident photons within the singlet fission material to form singlet excitons, which then undergo efficient singlet fission in the solution phase (135 +/- 5%) before quantitative harvesting of the triplet excitons (95 +/- 5%) via a low concentration of QD acceptors, followed by the emission of IR photons. We find that in order to achieve efficient triplet harvesting it is critical to engineer the surface of the QD with a triplet transfer ligand and that bimolecular decay of triplets is potentially a major loss pathway which can be controlled via tuning the concentration of QD acceptors. We demonstrate that the photon multiplication efficiency is maintained up to solar fluence. Our results establish the solution-based SF-PM system as a simple and highly tunable platform to understand the dynamics of a triplet energy transfer process between organic semiconductors and QDs, one that can provide clear design rules for new materials.
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| 5. |
- Gray, Victor, Dr, 1988-, et al.
(author)
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Direct vs Delayed Triplet Energy Transfer from Organic Semiconductors to Quantum Dots and Implications for Luminescent Harvesting of Triplet Excitons
- 2020
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In: ACS Nano. - : AMER CHEMICAL SOC. - 1936-0851 .- 1936-086X. ; 14:4, s. 4224-4234
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Journal article (peer-reviewed)abstract
- Hybrid inorganic-organic materials such as quantum dots (QDs) coupled with organic semiconductors have a wide range of optoelectronic applications, taking advantage of the respective materials' strengths. A key area of investigation in such systems is the transfer of triplet exciton states to and from QDs, which has potential applications in the luminescent harvesting of triplet excitons generated by singlet fission, in photocatalysis and photochemical upconversion. While the transfer of energy from QDs to the triplet state of organic semiconductors has been intensely studied in recent years, the mechanism and materials parameters controlling the reverse process, triplet transfer to QDs, have not been well investigated. Here, through a combination of steady-state and time-resolved optical spectroscopy we study the mechanism and energetic dependence of triplet energy transfer from an organic ligand (TIPS-tetracene carboxylic acid) to PbS QDs. Over an energetic range spanning from exothermic (-0.3 eV) to endothermic (+0.1 eV) triplet energy transfer we find that the triplet energy transfer to the QD occurs through a single step process with a clear energy dependence that is consistent with an electron exchange mechanism as described by Marcus-Hush theory. In contrast, the reverse process, energy transfer from the QD to the triplet state of the ligand, does not show any energy dependence in the studied energy range; interestingly, a delayed formation of the triplet state occurs relative to the quantum dots' decay. Based on the energetic dependence of triplet energy transfer we also suggest design criteria for future materials systems where triplet excitons from organic semiconductors are harvested via QDs, for instance in light emitting structures or the harvesting of triplet excitons generated via singlet fission.
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