The Experts below are selected from a list of 17295 Experts worldwide ranked by ideXlab platform
Nir Tessler - One of the best experts on this subject based on the ideXlab platform.
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molecular control of quantum dot Internal Electric Field and its application to cdse based solar cells
Nature Materials, 2011Co-Authors: Nir Yaacobigross, Marina Zimin, Shifi Kababya, Asher Schmidt, Michal Soreniharari, Nir TesslerAbstract:Inorganic nanocrystals are attractive materials for solar-cell applications. However, their performance is often limited by an insufficient alignment of Internal energy levels. A tuning of these energy levels has now been achieved by attaching two different molecules to a single nanocrystal, which significantly alters its electronic and optoelectronic properties.
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Molecular control of quantum-dot Internal Electric Field and its application to CdSe-based solar cells
Nature Materials, 2011Co-Authors: Nir Yaacobi-gross, Marina Zimin, Shifi Kababya, Asher Schmidt, Michal Soreni-harari, Nir TesslerAbstract:Inorganic nanocrystals are attractive materials for solar-cell applications. However, the performance of such devices is often limited by an insufficient alignment of energy levels in the nanocrystals. Here, we report that by attaching two different molecules to a single quantum dot or nanocrystal one can induce Electric Fields large enough to significantly alter the electronic and optoelectronic properties of the quantum dot. This Electric Field is created within the nanocrystals owing to a mixture of amine- and thiol-anchor-group ligands. Examining the steady state as well as temporal evolution of the optical properties and the nuclear magnetic resonances of the nanocrystals we found that the first excitonic peak shifts as a function of the capping-layer composition. We also demonstrate that the use of a mixed-ligand-induced Electric Field markedly enhances the charge generation efficiency in layer-by-layer CdSe-nanocrystal-based solar cells, thus improving the overall cell efficiency.
Jinfeng Zhang - One of the best experts on this subject based on the ideXlab platform.
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new understanding on the different photocatalytic activity of wurtzite and zinc blende cds
Applied Catalysis B-environmental, 2016Co-Authors: Jinfeng Zhang, S Wageh, Ahmeda AlghamdiAbstract:Abstract In general, wurtzite CdS exhibits a higher photocatalytic activity than zinc-blende CdS. However, the underlying physicochemical reasons responsible for the differences of photocatalytic activity between the wurtzite and zinc-blende CdS are still unclear. In this work, the structural characteristics, band structures, density of states, bond populations, optical properties and charge carrier effective mass of wurtzite and zinc-blende CdS were investigated based on first-principle theoretical calculations. The calculated results indicate that the distortion of CdS4 tetrahedron units results in the formation of Internal Electric Field in wurtzite CdS, which is beneficial for the efficient separation and diffusion of photogenerated charge carriers. Contrarily, the Internal Electric Field is absent in zinc-blende CdS. Moreover, the effective masses of photogenerated charge carriers of wurtzite CdS are smaller than those of zinc-blende CdS, implying faster migration of photogenerated charge carriers to perform photocatalytic reactions on wurtzite CdS surfaces. All the above factors result in the lower recombination rate of photogenerated charge carriers within wurtzite CdS. Therefore, it is not surprising that wurtzite CdS usually shows a higher photocatalytic activity than zinc-blende CdS. This investigation will provide some new understanding on the difference of photocatalytic activity between wurtzite and zinc-blende CdS.
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effect of effective mass and spontaneous polarization on photocatalytic activity of wurtzite and zinc blende zns
APL Materials, 2015Co-Authors: Ming Dong, Jinfeng ZhangAbstract:Semiconductor zinc sulphide (ZnS) has two common phases: hexagonal wurtzite and cubic zinc-blende structures. The crystal structures, energy band structures, density of states (DOS), bond populations, and optical properties of wurtzite and zinc-blende ZnS were investigated by the density functional theory of first-principles. The similar band gaps and DOS of wurtzite and zinc-blende ZnS were found and implied the similarities in crystal structures. However, the distortion of ZnS4 tetrahedron in wurtzite ZnS resulted in the production of spontaneous polarization and Internal Electric Field, which was beneficial for the transfer and separation of photogenerated electrons and holes.
Michael Groza - One of the best experts on this subject based on the ideXlab platform.
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effect of sub bandgap illumination on the Internal Electric Field of cdznte
Journal of Applied Physics, 2011Co-Authors: Aaron L Washington, Michael Groza, Lucile C Teague, Martine C Duff, A Burger, Vladimir BuligaAbstract:Post-growth manipulation of the Internal Electric Field in CdZnTe crystals using sub-bandgap illumination is measured as a function of temperature through infrared (IR) transmission measurements. Using near sub-bandgap IR illumination, both the optical de-trapping of charge carriers and the reduction in carrier recombination increased the mobility lifetime in the crystal. The increased carrier transport is a direct result of decreased hole and electron trapping in addition to other underlying mechanisms. Concentration of the Electric Field near the cathode is also observed. We measured the Electric Field distribution with sub-bandgap illumination as a function of temperature via the Pockels effect.
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investigation of the Internal Electric Field in cadmium zinc telluride detectors using the pockels effect and the analysis of charge transients
Journal of Applied Physics, 2010Co-Authors: Michael Groza, Yuehui Cui, H Krawczynski, Alfred Garson, J Martin, Kuen Lee, M Beilicke, Vladimir Buliga, Mingsheng Guo, Constantine CocaAbstract:The Pockels electro-optic effect can be used to investigate the Internal Electric Field in cadmium zinc telluride (CZT) single crystals that are used to fabricate room temperature x and gamma radiation detectors. An agreement is found between the Electric Field mapping obtained from Pockels effect images and the measurements of charge transients generated by alpha particles. The Pockels effect images of a CZT detector along two mutually perpendicular directions are used to optimize the detector response in a dual anode configuration, a device in which the symmetry of the Internal Electric Field with respect to the anode strips is of critical importance. The Pockels effect is also used to map the Electric Field in a CZT detector with dual anodes and an attempt is made to find a correlation with the simulated Electric potential in such detectors. Finally, the stress-induced birefringence effects seen in the Pockels images are presented and discussed.
Vladimir Buliga - One of the best experts on this subject based on the ideXlab platform.
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effect of sub bandgap illumination on the Internal Electric Field of cdznte
Journal of Applied Physics, 2011Co-Authors: Aaron L Washington, Michael Groza, Lucile C Teague, Martine C Duff, A Burger, Vladimir BuligaAbstract:Post-growth manipulation of the Internal Electric Field in CdZnTe crystals using sub-bandgap illumination is measured as a function of temperature through infrared (IR) transmission measurements. Using near sub-bandgap IR illumination, both the optical de-trapping of charge carriers and the reduction in carrier recombination increased the mobility lifetime in the crystal. The increased carrier transport is a direct result of decreased hole and electron trapping in addition to other underlying mechanisms. Concentration of the Electric Field near the cathode is also observed. We measured the Electric Field distribution with sub-bandgap illumination as a function of temperature via the Pockels effect.
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investigation of the Internal Electric Field in cadmium zinc telluride detectors using the pockels effect and the analysis of charge transients
Journal of Applied Physics, 2010Co-Authors: Michael Groza, Yuehui Cui, H Krawczynski, Alfred Garson, J Martin, Kuen Lee, M Beilicke, Vladimir Buliga, Mingsheng Guo, Constantine CocaAbstract:The Pockels electro-optic effect can be used to investigate the Internal Electric Field in cadmium zinc telluride (CZT) single crystals that are used to fabricate room temperature x and gamma radiation detectors. An agreement is found between the Electric Field mapping obtained from Pockels effect images and the measurements of charge transients generated by alpha particles. The Pockels effect images of a CZT detector along two mutually perpendicular directions are used to optimize the detector response in a dual anode configuration, a device in which the symmetry of the Internal Electric Field with respect to the anode strips is of critical importance. The Pockels effect is also used to map the Electric Field in a CZT detector with dual anodes and an attempt is made to find a correlation with the simulated Electric potential in such detectors. Finally, the stress-induced birefringence effects seen in the Pockels images are presented and discussed.
Constantine Coca - One of the best experts on this subject based on the ideXlab platform.
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investigation of the Internal Electric Field in cadmium zinc telluride detectors using the pockels effect and the analysis of charge transients
Journal of Applied Physics, 2010Co-Authors: Michael Groza, Yuehui Cui, H Krawczynski, Alfred Garson, J Martin, Kuen Lee, M Beilicke, Vladimir Buliga, Mingsheng Guo, Constantine CocaAbstract:The Pockels electro-optic effect can be used to investigate the Internal Electric Field in cadmium zinc telluride (CZT) single crystals that are used to fabricate room temperature x and gamma radiation detectors. An agreement is found between the Electric Field mapping obtained from Pockels effect images and the measurements of charge transients generated by alpha particles. The Pockels effect images of a CZT detector along two mutually perpendicular directions are used to optimize the detector response in a dual anode configuration, a device in which the symmetry of the Internal Electric Field with respect to the anode strips is of critical importance. The Pockels effect is also used to map the Electric Field in a CZT detector with dual anodes and an attempt is made to find a correlation with the simulated Electric potential in such detectors. Finally, the stress-induced birefringence effects seen in the Pockels images are presented and discussed.