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Quantum Capacitance
Quantum capacitance, also known as chemical capacitance and electrochemical capacitance C_\bar, was first theoretically introduced by Serge Luryi (1988), and is defined as the variation of electrical charge q with respect to the variation of electrochemical potential \bar, i.e., C_ = \frac. In the simplest example, if you make a parallel-plate capacitor where one or both of the plates has a low density of states, then the capacitance is ''not'' given by the normal formula for parallel-plate capacitors, C_e. Instead, the capacitance is lower, as if there was another capacitor in series, C_q. This second capacitance, related to the density of states of the plates, is the quantum capacitance and is represented by C_q. The equivalent capacitance is called electrochemical capacitance \frac = \frac + \frac. Quantum capacitance is especially important for low-density-of-states systems, such as a 2-dimensional electronic system in a semiconductor surface or interface or graphene, and ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electric Charge
Electric charge (symbol ''q'', sometimes ''Q'') is a physical property of matter that causes it to experience a force when placed in an electromagnetic field. Electric charge can be ''positive'' or ''negative''. Like charges repel each other and unlike charges attract each other. An object with no net charge is referred to as neutral particle, electrically neutral. Early knowledge of how charged substances interact is now called classical electrodynamics, and is still accurate for problems that do not require consideration of quantum mechanics, quantum effects. In an isolated system, the total charge stays the same - the amount of positive charge minus the amount of negative charge does not change over time. Electric charge is carried by subatomic particles. In ordinary matter, negative charge is carried by electrons, and positive charge is carried by the protons in the atomic nucleus, nuclei of atoms. If there are more electrons than protons in a piece of matter, it will have a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thomas–Fermi Screening
Thomas–Fermi screening is a theoretical approach to calculate the effects of electric field screening by electrons in a solid.N. W. Ashcroft and N. D. Mermin, ''Solid State Physics'' (Thomson Learning, Toronto, 1976) It is a special case of the more general Lindhard theory; in particular, Thomas–Fermi screening is the limit of the Lindhard theory, Lindhard formula when the wavevector (the reciprocal of the length-scale of interest) is much smaller than the Fermi wavevector, i.e. the long-distance limit. It is named after Llewellyn Thomas and Enrico Fermi. The Thomas–Fermi wavevector (in Gaussian units, Gaussian-cgs units) is k_0^2 = 4\pi e^2 \frac, where ''μ'' is the chemical potential (Fermi level), ''n'' is the electron concentration and ''e'' is the elementary charge. For the example of semiconductors that are not too heavily doped, the charge density , where ''k''B is Boltzmann constant and ''T'' is temperature. In this case, k_0^2 = \frac, i.e. is given by the familia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Supercapacitor
alt=Supercapacitor, upright=1.5, Schematic illustration of a supercapacitor upright=1.5, A diagram that shows a hierarchical classification of supercapacitors and capacitors of related types A supercapacitor (SC), also called an ultracapacitor, is a high-capacity capacitor, with a capacitance value much higher than solid-state capacitors but with lower voltage limits. It bridges the gap between electrolytic capacitors and rechargeable batteries. It typically stores 10 to 100 times more energy per unit volume or mass than electrolytic capacitors, can accept and deliver charge much faster than batteries, and tolerates many more charge and discharge cycles than rechargeable batteries. Unlike ordinary capacitors, supercapacitors do not use the conventional solid dielectric, but rather, they use electrostatic double-layer capacitance and electrochemical pseudocapacitance, both of which contribute to the total energy storage of the capacitor. Supercapacitors are used in applica ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Capacitance–voltage Profiling
Capacitance–voltage profiling (or C–V profiling, sometimes CV profiling) is a technique for characterizing semiconductor materials and devices. The applied voltage is varied, and the capacitance is measured and plotted as a function of voltage. The technique uses a metal–semiconductor junction (Schottky barrier) or a p–n junctionJ. Hilibrand and R.D. Gold, "Determination of the Impurity Distribution in Junction Diodes From Capacitance-Voltage Measurements", RCA Review, vol. 21, p. 245, June 1960 or a MOSFET to create a depletion region, a region which is empty of conducting electrons and holes, but may contain ionized donors and electrically active defects or ''traps''. The depletion region with its ionized charges inside behaves like a capacitor. By varying the voltage applied to the junction it is possible to vary the depletion width. The dependence of the depletion width upon the applied voltage provides information on the semiconductor's internal characteristics, such a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Juan Bisquert
Juan Bisquert (Düsseldorf, 1962), is a Spanish physicist known for his contributions to materials and devices for sustainable energy production. He grew up in Dénia, and he is a professor at Jaume I University in Castellón de la Plana. His work on solar cells relates physical principles and modelling of electronic and ionic processes to the interpretation of measurement techniques for the photovoltaic operation. Research activity At Universitat Jaume I he is the funding director of INAM (Institute of Advanced Materials), that develops research on materials, nanostructures and devices for the production of clean energy. He has published more than 400 papers in scientific journals. He has been cited more than 40,000 times in scientific journals. From 2014 to 2022 he appeared in the list " ISI Highly Cited Researchers" He wrote a series of books that have been published in the single volume "The Physics of Solar Energy Conversion". He edited the monography Photoelectrochem ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nanoparticle
A nanoparticle or ultrafine particle is a particle of matter 1 to 100 nanometres (nm) in diameter. The term is sometimes used for larger particles, up to 500 nm, or fibers and tubes that are less than 100 nm in only two directions. At the lowest range, metal particles smaller than 1 nm are usually called atom clusters instead. Nanoparticles are distinguished from microparticles (1-1000 μm), "fine particles" (sized between 100 and 2500 nm), and "coarse particles" (ranging from 2500 to 10,000 nm), because their smaller size drives very different physical or chemical properties, like colloidal properties and ultrafast optical effects or electric properties. Being more subject to the Brownian motion, they usually do not sediment, like colloid, colloidal particles that conversely are usually understood to range from 1 to 1000 nm. Being much smaller than the wavelengths of visible light (400-700 nm), nanoparticles cannot be seen with ordinary ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
TiO2
Titanium dioxide, also known as titanium(IV) oxide or titania , is the inorganic compound derived from titanium with the chemical formula . When used as a pigment, it is called titanium white, Pigment White 6 (PW6), or CI 77891. It is a white solid that is insoluble in water, although mineral forms can appear black. As a pigment, it has a wide range of applications, including paint, sunscreen, and food coloring. When used as a food coloring, it has E number E171. World production in 2014 exceeded 9 million tonnes. It has been estimated that titanium dioxide is used in two-thirds of all pigments, and pigments based on the oxide have been valued at a price of $13.2 billion. Structure In all three of its main dioxides, titanium exhibits octahedral geometry, being bonded to six oxide anions. The oxides in turn are bonded to three Ti centers. The overall crystal structures of rutile and anatase are tetragonal in symmetry whereas brookite is orthorhombic. The oxygen substructure ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sintered
Sintering or frittage is the process of compacting and forming a solid mass of material by pressure or heat without melting it to the point of liquefaction. Sintering happens as part of a manufacturing process used with metals, ceramics, plastics, and other materials. The atoms/molecules in the sintered material diffuse across the boundaries of the particles, fusing the particles together and creating a solid piece. Since the sintering temperature does not have to reach the melting point of the material, sintering is often chosen as the shaping process for materials with extremely high melting points, such as tungsten and molybdenum. The study of sintering in metallurgical powder-related processes is known as powder metallurgy. An example of sintering can be observed when ice cubes in a glass of water adhere to each other, which is driven by the temperature difference between the water and the ice. Examples of pressure-driven sintering are the compacting of snowfall to a gl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dye-sensitized Solar Cells
A dye-sensitized solar cell (DSSC, DSC, DYSC or Grätzel cell) is a low-cost solar cell belonging to the group of thin film solar cells. It is based on a semiconductor formed between a photo-sensitized anode and an electrolyte, a ''Photoelectrochemical cell, photoelectrochemical'' system. The modern version of a dye solar cell, also known as the Grätzel cell, was originally co-invented in 1988 by Brian O'Regan (chemist), Brian O'Regan and Michael Grätzel at University of California, Berkeley, UC Berkeley and this work was later developed by the aforementioned scientists at the École Polytechnique Fédérale de Lausanne, École Polytechnique Fédérale de Lausanne (EPFL) until the publication of the first high efficiency DSSC in 1991. Michael Grätzel has been awarded the 2010 Millennium Technology Prize for this invention. The DSSC has a number of attractive features; it is simple to make using conventional roll-printing techniques, is semi-flexible and semi-transparent which ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbon Nanotubes
A carbon nanotube (CNT) is a tube made of carbon with a diameter in the nanometre range (nanoscale). They are one of the allotropes of carbon. Two broad classes of carbon nanotubes are recognized: * ''Single-walled carbon nanotubes'' (''SWCNTs'') have diameters around 0.5–2.0 nanometer, nanometres, about 100,000 times smaller than the width of a human hair. They can be idealised as cutouts from a two-dimensional graphene sheet rolled up to form a hollow cylinder. * ''Multi-walled carbon nanotubes'' (''MWCNTs'') consist of nested single-wall carbon nanotubes in a nested, tube-in-tube structure. Double- and triple-walled carbon nanotubes are special cases of MWCNT. Carbon nanotubes can exhibit remarkable properties, such as exceptional tensile strength and thermal conductivity because of their nanostructure and bond strength, strength of the bonds between carbon atoms. Some SWCNT structures exhibit high electrical conductivity while others are semiconductors. In addition, ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Effective Mass (solid-state Physics)
In solid state physics, a particle's effective mass (often denoted m^*) is the mass that it ''seems'' to have when responding to forces, or the mass that it seems to have when interacting with other identical particles in a thermal distribution. One of the results from the band theory of solids is that the movement of particles in a periodic potential, over long distances larger than the lattice spacing, can be very different from their motion in a vacuum. The effective mass is a quantity that is used to simplify band structures by modeling the behavior of a free particle with that mass. For some purposes and some materials, the effective mass can be considered to be a simple constant of a material. In general, however, the value of effective mass depends on the purpose for which it is used, and can vary depending on a number of factors. For electrons or electron holes in a solid, the effective mass is usually stated as a factor multiplying the rest mass of an electron, ''m'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Internal Chemical Potential
In thermodynamics, the chemical potential of a species is the energy that can be absorbed or released due to a change of the particle number of the given species, e.g. in a chemical reaction or phase transition. The chemical potential of a species in a mixture is defined as the rate of change of free energy of a thermodynamic system with respect to the change in the number of atoms or molecules of the species that are added to the system. Thus, it is the partial derivative of the free energy with respect to the amount of the species, all other species' concentrations in the mixture remaining constant. When both temperature and pressure are held constant, and the number of particles is expressed in moles, the chemical potential is the partial molar Gibbs free energy. At chemical equilibrium or in phase equilibrium, the total sum of the product of chemical potentials and stoichiometric coefficients is zero, as the free energy is at a minimum. In a system in diffusion equilibrium, the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
