As solar power usage is increasing nowadays, performance tests have become one of the most important topics in order to guarantee the security of photovoltaic tools. For photovoltaic panels to become efficient, there is need for health testing of all materials and technologies used in the production of the panels in electrical and optical aspects. Thus, when future energy standards are considered, it is imperative to use solar simulators that obtain near real sunlight spectrum values. The most important components of solar simulators used in photovoltaic panel tests are light sources. In this study, solar simulators were classified based on the light sources they use, and their history and technological development were investigated in line with the literature. Within the scope of this study, carbon arc lamps, sodium vapor lamps, argon arc lamps, quartz-tungsten halogen lamps, mercury xenon lamps, xenon arc, xenon flash lamps, metal halide lamps, LED and super continuum laser light sources were investigated. Additionally, to compare spectral deficiency among these light sources and solar simulators, multiple light sourced solar simulators were also covered under a separate title.

Light sources of solar simulators for photovoltaic devices: A review

In this letter, an ellipsoid–spherical combined light source structure is presented for the purpose of uniform flux and color mixing, when considering heat dissipation. To allow more rays couple into spherical chamber while keeping illumination uniformity, algebraic equations to estimate light spot size focused by ellipsoidal reflector are derived and then employed to decide input slot size of the chamber. Then Monte Carlo ray tracing simulation suggests that the most preferable output slot size is between 15% and 30% of the chamber radius when considering both uniformity and available test area. A prototype with a 150-W Xenon arc lamp is fabricated to demonstrate heat distribution for the system, and experiment about uniformity indicates that 89.4% of the test circle radius can reach 2% nonuniformity. Color mixing performance for the system is studied by equipped with three ellipsoidal reflectors to collect rays from different color LEDs, and experiment shows that the maximum root-mean-square error of the spectrum across 90% of output circle radius is 1.4%. Results demonstrate it is a structure with simplified design process and having less dependence with light source type.

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Design of Ellipsoid and Spherical Combined Light Source for Uniform Flux and Color Mixing

Even though graphene is a low-energy system consisting of a two-dimensional honeycomb lattice of carbon atoms, its quasiparticle excitations are fully described by the (2+1)-dimensional relativistic Dirac equation. In this paper we show that, while the spin-orbit interaction in graphene is of the order of 4 meV, it opens up a gap of the order of 10(-3) meV at the Dirac points. We present a first-principles calculation of the spin-orbit gap, and explain the behavior in terms of a simple tight-binding model. Our result also shows that the recently predicted quantum spin Hall effect in graphene can occur only at unrealistically low temperature.

Spin-orbit gap of graphene: First-principles calculationsYugui Yao

The structural and electronic properties of graphene/graphene-like Aluminum Nitrides monolayer (Gr/g-AlN) heterojunction with and without vacancies are systematically investigated by first-principles calculation. The results prove that Gr/g-AlN with nitrogen-vacancy (Gr/g-AlN-VN) is energy favorable with the smallest sublayer distance and binding energy. Gr/g-AlN-VN is nonmagnetic, like that in the pristine Gr/g-AlN structure, but it is different from the situation of g-AlN-VN, where a magnetic moment of 1 μB is observed. The metallic graphene acts as an electron acceptor in the Gr/g-AlN-VN and donor in Gr/g-AlN and Gr/g-AlN-VAl contacts. Schottky barrier height Φ B , n by traditional (hybrid) functional of Gr/g-AlN, Gr/g-AlN-VAl, and Gr/g-AlN-VN are calculated as 2.35 (3.69), 2.77 (3.23), and 1.10 (0.98) eV, respectively, showing that vacancies can effectively modulate the Schottky barrier height. Additionally, the biaxial strain engineering is conducted to modulate the heterojunction contact properties. The pristine Gr/g-AlN, which is a p-type Schottky contact under strain-free condition, would transform to an n-type contact when 10% compressive strain is applied. Ohmic contact is formed under a larger tensile strain. Furthermore, 7.5% tensile strain would tune the Gr/g-AlN-VN from n-type to p-type contact. These plentiful tunable natures would provide valuable guidance in fabricating nanoelectronics devices based on Gr/g-AlN heterojunctions.

https://www.mdpi.com/2079-4991/9/12/1674/pdf

Tunable Electronic Properties of Graphene/g-AlN Heterostructure: The Effect of Vacancy and Strain Engineering

Using density functional theory, we investigate a novel two-dimensional silicon bismotide (SiBi) that has a layered GaSe-like crystal structure. Ab initio molecular dynamic simulations and phonon dispersion calculations suggest its good thermal and dynamical stability. The SiBi monolayer is a semiconductor with a narrow indirect bandgap of 0.4 eV. Our results show that the indirect bandgap decreases as the number of layers increases, and when the number of layers is more than six layers, direct-to-indirect bandgap switching occurs. The SiBi bilayer is found to be very sensitive to an E-field. The bandgap monotonically decreases in response to uniaxial and biaxial compressive strain, and reaches 0.2 eV at 5%, while at 6%, the semiconductor becomes a metal. For both uniaxial and biaxial tensile strains, the material remains a semiconductor and indirect-to-direct bandgap transition occurs at a strain of 3%. Compared to a SiBi monolayer with a layer thickness of 4.89 A, the bandgap decreases with either increasing or decreasing layer thickness, and at a thicknesses of 4.59 to 5.01 A, the semiconductor-to-metal transition happens. In addition, under pressure, the semiconducting character of the SiBi bilayer with a 0.25 eV direct bandgap is preserved. Our results demonstrate that the SiBi nanosheet is a promising candidate for designing high-speed low-dissipation devices.

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Two-dimensional silicon bismotide (SiBi) monolayer with a honeycomb-like lattice: first-principles study of tuning the electronic properties

Structural, mechanical, and electronic properties of 25 kinds of III-V binary monolayers: A computational study with first-principles calculation

In this paper, a regular dodecahedron solar simulator structure with five spot light sources is presented to provide uniform flux. To analyze light distribution without a dodecahedron cavity, a cubic cosine relationship between deflection angle and test flat plane is proposed, and results show that nonuniformity reaches 5%. By introducing a regular dodecahedron cavity, nonuniformity can be reduced to 2% in a circular area with an 85% inradius, according to the Monte Carlo ray tracing method. Based on the structure, a prototype simulator is fabricated by pentagons with 4 cm inradius and with five high-power light-emitting diodes (LEDs). Across the inscribed circular aperture of the bottom light output pentagon, nonuniformity is 3.1%; while 2% nonuniformity is reached in a 3.4-cm2 circular aperture whose area occupies 72% of the inscribed circle.

A Multisource Regular Dodecahedron Solar Simulator Structure for Uniform Flux

The optical properties of surface and bulk InxGa1-xAs materials are compared systematically first time in this paper. The band structures, density of states and optical properties including dielectric function, reflectivity, absorption coefficient, loss function and refractive index of bulk and surface InxGa1-xAs materials are investigated by first-principles based on plane-wave pseudo-potentials method within the LDA approximation. The results agree well with the available theoretical and experimental studies and indicate that the electronic and optical properties of bulk and surface InxGa1-xAs materials are much different, and the results show that the considered optical properties of the both materials vary with increasing indium composition in an opposite way. The calculations show that the optical properties of surface In0.75Ga0.25As material are unexpected to be far from the other two indium compositions of surface InxGa1-xAs materials while the optical properties of bulk InxGa1-xAs materials vary with increasing indium composition in an expected regular way.

Theoretical study on the electronic and optical properties of bulk and surface (001) In x Ga 1-x As

The magnetic and optical properties studies in monolayer transition-metal dichalcogenides have attracted attention because of the manufacture spintronic, electronic and photonic device. This paper reported the magnetism and optical properties of Mn-O, Mn-Se, Mn-Te, Mn-Po co-doped MoS2 monolayer systems via first principle calculation, results shows Mn-X(X=O, Se, Te and Po) co-doped MoS2 monolayer systems appear half-metal (HM) ferromagnet, their corresponding magnetic moments are 1.06μB, 1.04μB, 1.04μB, 1.03μB，respectively. The co-doped systems have smaller bandgaps due to effective charge compensation among Mn-O, Mn-Se, Mn-Te and Mn-Po atoms. According to calculation, we find Mn-O co-doped MoS2 monolayer has the lowest formation energy in four co-doping systems, thus the Mn-O co-doped MoS2 monolayer has the best stability. The Mn-Se co-doped MoS2 monolayer has the highest static dielectric constants and , refractive index and . In energy range of 0 to 1.5 eV, the transmittance of intrinsic MoS2 system is higher than that of all co-doped MoS2 systems obtained by absorption coefficient.

https://iopscience.iop.org/article/10.1088/2053-1591/abc5df/pdf

The magnetic, optical and electronic properties of Mn–X(X = O, Se, Te, Po) co-doped MoS2 monolayers via first principle calculation

The utility model provides an appointment arranging state recognition system which comprises an entrance gate device, an exit gate device, a network device, an arranging server and a number calling terminal. The entrance gate device and the exit gate device are connected with the arranging server through the network device, the arranging server is connected with the number calling terminal, the entrance gate device is used for acquiring business information inputted by users and transmitting the business information to the network device, the business information is transmitted to the arranging server by the network device, the exit gate device is arranged in an appointment arranging system and used for acquiring arranging cards, a current arranging card is canceled or frozen by the arranging server, and the appointment arranging state recognition system solves the technical problem that an appointment arranging system in the prior art cannot effectively recognize states of appointed customers, and cannot immediately cope with vacant numbers generated in arranging.

Wang Yi

Papers

Structural, mechanical, and electronic properties of 25 kinds of III-V binary monolayers: A computational study with first-principles calculation

A Multisource Regular Dodecahedron Solar Simulator Structure for Uniform Flux

Theoretical study on the electronic and optical properties of bulk and surface (001) In x Ga 1-x As

The magnetic, optical and electronic properties of Mn–X(X = O, Se, Te, Po) co-doped MoS2 monolayers via first principle calculation

Appointment arranging state recognition system