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Photovoltaics
Published in Robert Ehrlich, Harold A. Geller, John R. Cressman, Renewable Energy, 2023
Robert Ehrlich, Harold A. Geller, John R. Cressman
Doping a semiconductor is the deliberate addition of impurity atoms into the pure semiconductor in order to change its electrical properties, especially its conductivity. Doped semiconductors are also known as extrinsic semiconductors in contrast to pure or intrinsic semiconductors. Typically, the level of doping is quite small, e.g., light doping might entail adding one impurity (dopant) atom per 100 million atoms, while heavy doping might entail one dopant atom per 10,000 atoms. The best doping concentration for silicon solar cells so as to achieve maximum power output has been found to lie in the range of 1017–1018 dopant atoms/cm3, which is equivalent to about one atom in 104–105 (Iles and Soclof, 1975). Silicon is used for about 95% of solar cells produced, given its low cost and the size of its bandgap, which as we shall see is nearly optimal in terms of efficiency for converting solar radiation into electricity.
Measurement
Published in William H. Hallenbeck, Radiation Protection, 2020
A semiconductor is a solid crystalline material that has an electrical conductivity between that of an insulator and a good conductor such as metal. The electrical conductivity of a semiconductor changes when it is exposed to radiation. The performance characteristics of scintillator and semiconductor detectors are commonly compared to those of Nal. The energy resolution of semiconductor detectors is much better than that of Nal. However, the counting efficiency is lower than that of Nal crystals.
Direct Current (dc) Electronics
Published in Dale R. Patrick, Stephen W. Fardo, Electricity and Electronics Fundamentals, 2020
Dale R. Patrick, Stephen W. Fardo
Materials called semiconductors have become very important in electronics. Semiconductor materials are neither conductors nor insulators. Their classification also depends on the number of electrons their atoms have in their valence shells. Semiconductors have 4 electrons in their valence shells. Remember that conductors have outer orbits less than half-filled and insulators ordinarily have outer orbits more than half-filled. Figure 1-12 compares conductors, insulators, and semiconductors. Some common types of semiconductor materials are silicon, germanium, and selenium.
Surface waves in piezoelectric semiconductor by using Eigen value approach
Published in Waves in Random and Complex Media, 2023
Adnan Jahangir, Sayed M. Abo-Dahab, Aiman Iqbal
Piezoelectric materials are materials that have the ability to create inner electrical charge from applied mechanical stress. Piezo is a Greek word used for ‘push’. A few normally happening substances in nature show the piezoelectric impact. These are DNA, Enamel, Silk, certain ceramics, crystals, Bone, Dentine and many more. The conductivity of semiconductors is in between insulators and good conductors, and it increments with expansion in temperature. A pure semiconductor, accordingly, acts as an insulator. The resistance of a semiconductor decreases with expansion in temperature. In a pure semiconductor, which carries on like an insulator under standard conditions, if modest quantity of certain metallic impurity is added, it achieves current conducting properties. The impure semiconductor is then called ‘impurity semiconductor’ or ‘outward semiconductor’. The way toward adding impurity to a semiconductor to make it extrinsic semiconductor is called Doping.
Synthesis, characterization, photocatalytic activity, DNA interaction and antimicrobial studies of some lanthanide(III) complexes with a tridentate Schiff base ligand
Published in Journal of Coordination Chemistry, 2023
B. Shyni, T. S. Sikha, J. P. Remiya, Y. M. Thasneem, S. Suhara Beevy
The semiconducting properties of 1–3 are mainly provided by the photoactive organic ligands. In lanthanide metal complexes the Schiff base ligand acts as an antenna to capture visible light. After absorption of radiation, holes are left in the valence band and the electrons (e-) are stimulated to move into the conduction band of the photocatalyst, resulting in the formation of pairs of negative electrons and positive holes (h+). The energy difference between the valence band and the conduction band is referred to as the “band gap,” also known as the “photo-excited” state of the semiconductor or photocatalyst. The wavelength of the band gap must match the wavelength of the light in order for the photocatalyst to effectively absorb the light. After photo excitation, the excited electrons and holes travel to the photocatalyst surface. In the photocatalytic water splitting reaction they are created as a reducing agent and an oxidizing agent producing O2 and H2, respectively. A schematic illustration of the proposed mechanism for the evolution of hydrogen is illustrated in Scheme 2.
Excited state dynamics in a sodium and iodine co-doped lead telluride nanowire
Published in Molecular Physics, 2021
Kevin Gima, Talgat M. Inerbaev, D. S. Kilin
Semiconductors are utilised in modern technologies for cellphones, refrigerators, automobiles, microwaves and numerous other ones. Applying thermoelectric materials to semiconductors can convert their excess waste heat into electricity, thus improving their efficiency. Thermoelectric materials use a temperature gradient between heat source and heat sink to produce a current. The phenomenon, where an electric potential (Voltage) is produced in a thermoelectric material placed between heat source and heat sink, is known as the Seebeck effect. This effect is measured by a material’s figure of merit given by where S is the Seebeck coefficient, κ thermal conductivity, σ electrical conductivity, and T temperature [1]. One aims to maximise this parameter. Oftentimes one achieves such improvements by doping (adding impurities) various materials [2]. In case the free charges are positive (the material is p-type), positive charge will build up near the heat sink (on the cold end) which will have a positive potential. Similarly, negative free charges (n-type material) will produce a negative potential near the heat sink (at the cold end). See SI for details.