| 1. |
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- 2019
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Tidskriftsartikel (refereegranskat)
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| 2. |
- Tian, Lei, 1987-
(författare)
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Exploring Dye-Sensitized Mesoporous NiO Photocathodes : from Mechanism to Applications
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Increasing attention has been paid on solar energy conversion since the abundant solar energy possesses the potential to solve the problems on energy crisis and climate change. Dye-sensitized mesoporous NiO film was developed as one of the attractive photocathodes to fabricate p-type dye-sensitized solar cells (p-DSCs) and dye-sensitized photoelectrosynthetic cells (p-DSPECs) for electricity and chemical fuels generation, respectively. In this thesis, we designed a well-structured NiO-dye-TiO2 configuration by an atomic layer deposition (ALD) technique, with an organic dye PB6 as the photosensitizer. From kinetic studies of charge separation, ultrafast hole injection (< 200 fs) was observed from the excited state of PB6 dye into the valence band of NiO; dye regeneration (electron injection) was in t1/2 ≤ 500 fs, which is the fastest reported in any DSCs. On the basis of NiO-dye-TiO2 configuration, we successfully fabricated solid-state p-type DSCs (p-ssDSCs). Insertion of an Al2O3 layer was adopted to reduce charge recombination, i.e. NiO-dye-Al2O3-TiO2. Theoretically, such a configuration is possible to maintain efficient charge separation and depressed charge recombination. Based on NiO-dye-Al2O3-TiO2 configuration, the open-circuit voltage was improved to 0.48 V. Replacing electron conductor TiO2 with ZnO, short-circuit current density was increased to 680 μA·cm-2. The photocatalytic current density for H2 evolution was improve to 100 μA·cm-2 with a near unity of Faraday efficiency in p-DSPECs.However, to further improve the performance of p-DSCs is very challenging. In p-ssDSCs, the limitation was confirmed from the poor electronically connection of the electron conductor (TiO2 or ZnO) inside the NiO-dye films. We further investigated the electronic property of surface states on mesoporous NiO film. We found that the surface sates, not the bulk, on NiO determined the conductivity of the mesoporous NiO films. The dye regeneration in liquid p-DSCs with I-/I3- as redox couples was significantly affected by surface states. A more complete mechanism is suggested to understand a particular hole transport behavior reported in p-DSCs, where hole transport time is independent on light intensity. The independence of charge transport is ascribed to the percolation effect in the hole hopping on the surface states.
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| 3. |
- Hu, Lei, et al.
(författare)
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Molecular surface modification of silver chalcogenolate clusters
- 2022
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Ingår i: Dalton Trans.. - : Royal Society of Chemistry (RSC). ; 51, s. 3241-3247
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Tidskriftsartikel (refereegranskat)abstract
- This study presents a molecular surface modification approach to synthesizing a family of silver chalcogenolate clusters (SCCs) containing the same [Ag12S6] core and different surface-bonded organic ligands (DMAc or pyridines; DMAc = dimethylacetamide), with the aim of tuning the luminescence property and increasing the structural stability of the SCCs. The SCCs displayed strong and tuneable luminescence emissions at 77 K (from green to orange to red) as influenced by the peripheral pyridine ligands. In addition, SCC 5 protected by pyridine molecules was stable in ambient air, humid air and even liquid water for a long time (up to 1 week), and it was more structurally stable than SCC 1 bonded with DMAc molecules under the same conditions. The high structural stability of SCC 5 can be explained by the ability of pyridine molecules to form strong coordination bonds with silver atoms. This study offers a new way of designing structurally stable metal nanoclusters with tuneable physicochemical properties.
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| 4. |
- Li, Biwen, et al.
(författare)
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Electrochemical versus Photoelectrochemical Water Oxidation Kinetics on Bismuth Vanadate (Photo)anodes
- 2024
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Ingår i: Journal of the American Chemical Society. - 0002-7863 .- 1520-5126. ; 146:18, s. 12324-12328
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Tidskriftsartikel (refereegranskat)abstract
- This study reports a comparison of the kinetics of electrochemical (EC) versus photoelectrochemical (PEC) water oxidation on bismuth vanadate (BiVO4) photoanodes. Plots of current density versus surface hole density, determined from operando optical absorption analyses under EC and PEC conditions, are found to be indistinguishable. We thus conclude that EC water oxidation is driven by the Zener effect tunneling electrons from the valence to conduction band under strong bias, with the kinetics of both EC and PEC water oxidation being determined by the density of accumulated surface valence band holes. We further demonstrate that our combined optical absorption/current density analyses enable an operando quantification of the BiVO4 photovoltage as a function of light intensity.
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| 5. |
- Tian, Ke, et al.
(författare)
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Blue band nonlinear optics and photodarkening in silica microdevices
- 2022
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Ingår i: Photonics Research. - 2327-9125. ; 10:9, s. 2073-2080
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Tidskriftsartikel (refereegranskat)abstract
- There are extensive studies to date on optical nonlinearities in microcavities at the near and mid-IR wavelengths. Pushing this research into the visible region is equally valuable. Here, we demonstrate a directly pumped, blue band Kerr frequency comb and stimulated Raman scattering (SRS) at 462 nm in a silica nanofiber-coupled whispering gallery microcavity system. Notably, due to the high optical intensities achieved, photodarkening is unavoidable and can quickly degrade the optical quality of both the coupling optical nanofiber and the microcavity, even at very low pump powers. Nonetheless, stable hyperparametric oscillation and SRS are demonstrated in the presence of photodarkening by taking advantage of in-situ thermal bleaching. This work highlights the challenges of silica-based, short wavelength nonlinear optics in high-quality, small mode volume devices and gives an effective method to overcome this apparent limitation, thus providing a baseline for optics research in the blue region for any optical devices fabricated from silica.
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