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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Terahertz-Driven Luminescence and Colossal Stark Effect in CdSe–CdS Colloidal Quantum Dots
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Terahertz-Driven Stark Spectroscopy of CdSe and CdSe–CdS Core–Shell Quantum Dots
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Favorable Bonding and Band Structures of Cu[subscript 2]ZnSnS[subscript 4] and CdS Films and Their P
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Subpicosecond Photoinduced Hole Transfer from a CdS Quantum Dot to a Molecular Acceptor Bound Through an Exciton-Delocalizing Ligand
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Electron Transfer Kinetics in CdS Nanorod-[FeFe]-Hydrogenase Complexes and Implications for Photochemical H2 Generation
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Competition Between Electron Transfer, Trapping, and Recombination in CdS Nanorod-Hydrogenase Complexes
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Performance and limits of 2.0 eV bandgap CuInGaS 2 solar absorber integrated with CdS buffer on F:SnO 2 substrate for multijunction photovoltaic and photoelectrochemical water splitting devices
Photocurrent density in excess of 10 mA cm −2 reported on 2.0 eV CuInGaS 2 solar cells integrated on SnO 2 :F substrates, yet new wide bandgap n-type buffers required to achieve higher photoconversion efficiency.
First principles DFT study of dye-sensitized CdS quantum dots
Dye-sensitized quantum dots (QDs) are considered promising candidates for dye-sensitized solar cells. In order to maximize their efficiency, detailed theoretical studies are important. Here, we report a first principles density functional theory (DFT) investigation of experimentally realized dye - sensitized QD / ligand systems, viz., Cd{sub 16}S{sub 16}, capped with acetate molecules and a coumarin dye. The hybrid B3LYP functional and a 6−311+G(d,p)/LANL2dz basis set are used to study the geometric, energetic and electronic properties of these clusters. There is significant structural rearrangement in all the clusters studied - on the surface for the bare QD, and in the positions of the acetate / dye ligands for the ligated QDs. The density of states (DOS) of the bare QD shows states in the band gap, which disappear on surface passivation with the acetate molecules. Interestingly, in the dye-sensitised QD, the HOMO is found to be localized mainly on the dye molecule, while the LUMO is on the QD, as required for photo-induced electron injection from the dye to the QD.
Effect of a redox-mediating ligand shell on photocatalysis by CdS quantum dots
Semiconductor quantum dots (QDs) are efficient organic photoredox catalysts due to their high extinction coefficients and easily tunable band edge potentials. Despite the majority of the surface being covered by ligands, our understanding of the effect of the ligand shell on organic photocatalysis is limited to steric effects. We hypothesize that we can increase the activity of QD photocatalysts by designing a ligand shell with targeted electronic properties, namely, redox-mediating ligands. Herein, we functionalize our QDs with hole-mediating ferrocene (Fc) derivative ligands and perform a reaction where the slow step is hole transfer from QD to substrate. Surprisingly, we find that a hole-shuttling Fc inhibits catalysis, but confers much greater stability to the catalyst by preventing a build-up of destructive holes. We also find that dynamically bound Fc ligands can promote catalysis by surface exchange and creation of a more permeable ligand shell. Finally, we find that trapping the electron on a ligand dramatically increases the rate of reaction. Furthermore, these results have major implications for understanding the rate-limiting processes for charge transfer from QDs and the role of the ligand shell in modulating it.