Optical Energy Losses Research Articles

Controlled dynamic variation of interfacial electronic and optical properties of lithium intercalated ZrO2/MoS2 vdW heterostructure

Efficient strategies for modifying the characteristics of van der Waals (vdW) layered materials in a precise and reversible mode remain challenging. Our suggested method for customization entails the implementation of layer-sliding and intercalation. In this work, a norm-conserving approach within the context of density functional theory has been used to examine the electronic and optical properties of two-dimensional (2D) van der Waals heterostructure (vdWHS), which is modeled by using 2D zirconium dioxide (1T-ZrO2) and molybdenum disulfide (1T-MoS2) monolayers of similar phase. Both contributing monolayers have similar lattice structures, with a minimum lattice mismatch of 0.83 %, and have corrugation on both sides that can successfully retain foreign species at the vdW-gap. In the next step, interfacial engineering through Li-intercalation and layer-sliding was employed to modify physical properties of the vdWHS. It is the worth mentioning that a narrow bandgap of 0.102 eV (0.22 eV) has been observed in the unintercalated ZrO2/MoS2 vdWHS when employing PW-LDA (hybrid-functional). Li-intercalation and sliding process significantly influenced the electronic properties of the studied vdWHS. Furthermore, un-slided and fully-slided Li-intercalated vdWHS exhibit an increase in the vdW-gap by 3.78 % and 27.14 %, respectively, as compared to unintercalated vdWHS. To further understand the electrical behaviour at the interface of contributing monolayers, a comparative study has also been made for the variation in the planar average charge density difference, charge transfer, and interface dipole moment for unintercalated and intercalated vdWHS. In the unintercalated vdWHS, the calculated values of ΔQ and μ(z) provide evidence of significant charge transfer from 1T-ZrO2 to 1T-MoS2 before sliding, whereas in the fully-slided vdWHS, there is 80.11 % more charge transfer from 1T-MoS2 to 1T-ZrO2. Li-intercalation increases the magnitude of ΔQ (by 90.27 %) near 1T-MoS2, indicating a sufficient quantity of charge transfer from the 1T-MoS2 monolayer. The results of the anisotropic analysis show that the calculated in-plane and out-of-plane components of the real and imaginary parts of the dielectric function differ significantly. The optical absorption and energy losses of Li-intercalated vdWHS experience a substantial decrease of about 90 % and 50 %, respectively, as compared to unintercalated vdWHS. Our employed method promotes the notion that interfacial engineering through simultaneous layer-sliding and intercalation approach can be used to regulate and modify the physical properties of 2D insulator/metal based vdWHS.

Comprehensive Improvement of Various Features of Cu-Cd Ferrites (Cu0.5Cd0.5Fe2-xCexO4) by Cerium (Ce3+) Ion Substitution.

Cerium (Ce3+) substitution in Cu-Cd spinel nanoferrites with the compositional formula Cu0.5Cd0.5Fe2-xCexO4 (x = 0.0, 0.0125, 0.0250, 0.0375, 0.050) was performed by the hydrothermal route. The structural, morphological, optical, electrical, and dielectric properties of Ce-substituted Cu-Cd ferrites were explored. X-ray diffraction revealed the single-phase cubic structure of all nanoferrites. The average crystallite size (72.42-11.61 nm) and lattice constant (8.419-8.449 Å) were observed for the synthesized ferrites. The surface shapes of particles were determined by scanning electron microscopy. The substitution was also verified by Fourier transform infrared spectroscopy and ultraviolet-visible spectrophotometry. The semiconducting behavior of ferrites was determined from their electrical properties, such as direct current (DC) electrical resistivity. The Curie temperature was observed at 523 K temperature for all nanoferrites. The dielectric constant and dielectric loss significantly indicated the reducing behavior with an increase in the cerium concentration. The sample Cu0.5Cd0.5Fe1.975Ce0.025O4 resulted in the lowest optical bandgap energy, DC resistivity, and dielectric losses. The nature of the electrical resistivity and dielectric constants indicate that the designed materials are highly appropriate for the design of microwave gadgets.

Highly luminescent Gd2O2S:Er3+,Yb3+ upconversion microcrystals obtained by a time- and energy-saving microwave-assisted solid-state synthesis

Er3+-doped and Er3+,Yb3+-co-doped Gd2O2S are one of the most efficient upconversion (UC) materials available to date. However, preparing lanthanide oxysulfides can be challenging as it requires several hours of heating at>1000 °C in high power furnaces. Nonetheless, in designing a new synthesis technology for UC materials, one should consider that these systems suffer from defect quenching, responsible for significant optical energy losses. In this work, the microwave-assisted solid-state (MASS) synthesis was explored as an alternative to synthesize this class of materials, using two different starting compounds – lanthanide oxides (Ln2O3) and hydroxycarbonates (Ln(OH)CO3), where Ln3+: Gd, Er, Yb. Different Er3+,Yb3+ concentrations were investigated, and the Er3+(5%),Yb3+(5%) and Er3+(1%),Yb3+(10%) were shown to give the most intense UC output comparable to commercially available materials. Using Ln(OH)CO3 instead of the more common Ln2O3 for the MASS synthesis contributed to higher UC efficiencies and a more homogeneous Er3+ and especially Yb3+ distribution through the Gd2O2S lattice as verified by luminescence lifetime measurements. These high-quality materials were prepared in a simple two-step synthesis of 50 min and using a domestic microwave oven, leading to a remarkable decrease of 79% in processing time and 93% in energy consumption, making the MASS method suitable to be explored as an alternative synthesis methodology for high performance UC materials.

Gigahertz optoacoustic vibration in Sub-5 nm tip-supported nano-optomechanical metasurface

The gigahertz acoustic vibration of nano-optomechanical systems plays an indispensable role in all-optical manipulation of light, quantum control of mechanical modes, on-chip data processing, and optomechanical sensing. However, the high optical, thermal, and mechanical energy losses severely limit the development of nano-optomechanical metasurfaces. Here, we demonstrated a high-quality 5 GHz optoacoustic vibration and ultrafast optomechanical all-optical manipulation in a sub-5 nm tip-supported nano-optomechanical metasurface (TSNOMS). The physical rationale is that the design of the semi-suspended metasurface supported by nanotips of <5 nm enhances the optical energy input into the metasurface and closes the mechanical and thermal output loss channels, result in dramatically improvement of the optomechanical conversion efficiency and oscillation quality of the metasurface. The design strategy of a multichannel-loss-mitigating semi-suspended metasurface can be generalized to performance improvements of on-chip processed nano-optomechanical systems. Applications include all-optical operation of nanomechanical systems, reconfigurable nanophotonic devices, optomechanical sensing, and nonlinear and self-adaptive photonic functionalities.

Effect of nickel doping on the spectral sensitivity of silicon solar cells

In the modern industrial production of solar cells (SC), there is a growing trend to utilize “solar silicon” as the base material due to its cost-effectiveness. However, solar silicon possesses a drawback - it has a shorter lifetime of minority charge carriers (MCC), making it challenging to achieve high efficiency in solar cells. To address this limitation and improve the efficiency of solar cells based on “solar silicon,” two key objectives need to be met. Firstly, it is essential to increase the lifetime of photogenerated charge carriers. Secondly, there is a need to minimize both optical and electrical energy losses. To achieve an increase in the lifetime of minority charge carriers in SCs, a process called gettering can be employed. This process involves utilizing clusters of nickel atoms to trap uncontrolled impurity atoms. The paper presents the results of a study on the additional doping of silicon solar cells with nickel atoms, for factors affecting the long-wave and short-wave efficiency. Nickel doping has been shown to increase the efficiency of solar cells. It is determined that in the visible region of the spectrum the spectral sensitivity of a silicon solar cell doped with nickel is higher up to 25÷35% due to a decrease in surface recombination. Technological recommendations for nickel doping of single-crystal silicon solar cells are proposed to be combined without significant changes with the standard technological process for manufacturing solar cells.

Minimizing Optical Energy Losses for Long‐Lifetime Perovskite Light‐Emitting Diodes

AbstractRegardless of the rapid advance on perovskite light‐emitting diodes (PeLEDs), the lack of long‐term operational stability hinders the practicality of this technology. Particularly, thermal management is indispensable to control the Joule heating induced by charge transport and parasitic re‐absorption of internally confined photons. Herein, a synergetic device architecture is proposed for minimizing the optical energy losses in PeLEDs toward high efficiency and long lifetime. By adopting a carefully modified perovskite emitter in combination with an improved light outcoupling structure, red PeLEDs emitting at 666 nm achieve a peak external quantum efficiency of 21.2% and an operational half‐lifetime of 4806.7 h for an initial luminance of 100 cd m‐2. The enhanced light extraction from trapped modes can efficiently reduce the driving current and suppress optical energy losses in PeLEDs, which in turn ameliorate the heat‐induced device degradation during operation. This work paves the way toward high‐performance PeLEDs for display and lighting applications in the future.

Photon management strategies in SSM-DSCs: Realization of a >11% PCE device with a 2.3 V output

A sequential series multijunction dye-sensitized solar cell (SSM-DSC) designed to minimize optical and free energy losses to enable higher device performance is reported. Efficient photon management of solar spectrum irradiation was made possible by: controlling TiO2 film thickness in each subcell leading to balanced photocurrent, careful sensitizer selection based on absorption breadth and intensity for each subcell, and minimizing photon losses by application of an anti-reflective coating with an immersion oil between subcells. By using these strategies with a deep NIR absorbing sensitizer, an SSM-DSC device based on D35/B11/Black Dye demonstrated an overall power conversion efficiency of >11% with a photovoltage of 2.3 V from a single illuminated area device. The PCE of the SSM-DSC is significantly higher than any of the individual subcell in the mechanical stack. This approach has led to a higher performing device than the prior reported high efficiency SSM-DSC devices based on D35/B11/B11 or the all organic dye SSM-DSC based on D35/MK2/AP25 + D35.

Multipoint-Detection Strain Sensor with a Single Electrode Using Optical Ultrasound Generated by Carbon Nanotubes.

With the development of wearable devices, strain sensors have attracted large interest for the detection of human motion, movement, and breathing. Various strain sensors consisting of stretchable conductive materials have been investigated based on resistance and capacitance differences according to the strain. However, this method requires multiple electrodes for multipoint detection. We propose a strain sensor capable of multipoint detection with a single electrode, based on the ultrasound pulse–echo method. It consists of several transmitters of carbon nanotubes (CNTs) and a single polyvinylidene fluoride receiver. The strain sensor was fabricated using CNTs embedded in stretchable polydimethylsiloxane. The received data are characterized by the different times of transmission from the CNTs of each point depending on the strain, i.e., the sensor can detect the positions of the CNTs. This study demonstrates the application of the multipoint strain sensor with a single electrode for measurements up to a strain of 30% (interval of 1%). We considered the optical and acoustic energy losses in the sensor design. In addition, to evaluate the utility of the sensor, finger bending with three-point CNTs and flexible phantom bending with six-point CNTs for the identification of an S-curve having mixed expansion and compression components were carried out.

A strategy to boost external quantum efficiency of organic light-emitting transistors

Organic light-emitting transistors (OLETs) have emerged as promising light-emitting electronics, combining the functions of a transistor and a diode in a single device. OLETs typically possess outstanding electrical properties but have inefficient optical properties. Here, based on optical simulations, a strategy of how to improve the light output as well as reduce optical energy losses in OLETs is performed. The results reveal that the main optical energy losses occur via the waveguide mode by the organic layers and through absorption by the gate material. These energy losses in OLETs can be significantly reduced by appropriately adjusting the thicknesses and refractive indices of the transporting layers as well as those of the gate materials. This device design opens perspectives in the development of the efficiency of OLETs as high as 40% of external quantum efficiency.

Optical Energy Losses in Organic–Inorganic Hybrid Perovskite Light‐Emitting Diodes

AbstractLight‐emitting diodes (LEDs) based on organic–inorganic hybrid perovskites, in particular, 3D and quasi‐2D ones, are in the fast development and their external quantum efficiencies (EQEs) have exceeded 10%, making them competitive candidates toward large‐area and low‐cost light‐emitting applications allowing printing techniques. Similar to other LED categories, light out‐coupling efficiency is an important parameter determining the EQE of perovskite LEDs (PeLEDs), which, however, is scarcely studied, limiting further efficiency improvement and understanding of PeLEDs. In this work, for the first time, optical energy losses in PeLEDs are investigated through systematic optical simulations, which reveal that the 3D and quasi‐2D PeLEDs can achieve theoretically maximum EQEs of ≈25% and ≈20%, respectively, in spite of their high refractive indices. These results are consistent with the reported experimental data. This work presents primary understanding of the optical energy losses in PeLEDs and will spur new developments in the aspects of device engineering and light extraction techniques to boost the EQEs of PeLEDs.

Assessment of the erosion risk of sandstorms on solar energy technology at two sites in Morocco

This multi-disciplinary research paper should help solar power plant developers to perform an advanced site assessment in arid locations where the annual irradiance levels are high, but significant quantities of airborne sand and dust increase the risk of optical energy losses due to extinction, soiling, erosion damage (also known as abrasion), etc. Due to these effects sandstorms have a direct consequence on the operation and maintenance (O&M) costs. The work presented in the following characterizes airborne sand and dust material and later focuses on the resulting erosion effects. Some important meteorological and geological parameters for sandstorm occurrence and the resulting erosive damage on glass materials by impacting windblown material are extracted from literature. The respective parameters have been measured at two locations in Morocco (Zagora and Missour). After evaluation of wind and humidity data and a comprehensive soil analysis, the erosion risk was estimated to be higher in Zagora. The specular reflectance loss of exposed silvered-glass reflectors of 5.9% in Zagora and 0.8% in Missour after 25 months of exposure verified this estimation. Additionally, a specular reflectance analysis on a mirror sample that has been exposed for nine months in Kuwait is shown. On that sample specular reflectance losses of more than 40% were measured. A checklist with seven items is given in the conclusion to help solar plant developers to evaluate the risk of component aging due to sand storm erosion.

広帯域増感色素と有機金属ハライドペロブスカイトを用いた高効率有機系タンデム太陽電池

Tandem-type solar cell is a multiple-layered solar cell to decrease thermal- and optical-energy losses. However, typical organic photovoltaics has been difficult to apply tandem photovoltaics because of the lack of organic photovoltaic cells with high open-circuit voltage (VOC) and/or near-infrared (NIR) photoelectric conversion. In this study, we constructed tandem-type organic photovoltaics using high VOC organometal halide perovskite solar cell and NIR dye-sensitized solar cell. Consequently, over 16% power conversion efficiency which is highest record among tandem-type organic photovoltaics has been accomplished.

Design and Evaluation of a Compound Parabolic Concentrator for Heat Generation of Thermal Processes

A solar concentrator was designed using a detailed one-dimensional numerical model previously developed to describe the heat and fluid-dynamic behavior inside a compound parabolic concentrator (CPC). The governing equations (continuity, momentum and energy) inside the CPC absorber tube, together with the energy equation in the tube wall and the thermal analysis in the solar concentrator were solved.Two CPC geometries were proposed based on numerical simulation and commercial availability of materials; one of this is tested in this work.A ray tracing analysis was made for this configuration to quantify optical energy losses due to truncation. Then, a module with aperture area of 2.1 m2 was constructed. The module has 12 CPCs, each one with real concentration ratio of 1.8, acceptance angle of 30°, and a tubular receiver covered by a selective surface.An experimental setup was designed and built to test different operational conditions for the module; for example mass flow rate and inlet temperature. The experimental setup has the following elements: The CPC, two water storage tanks, a recirculation pump, and a support structure that allows positioning the CPC at different angles.Experimental results obtained using the Mexican standard NMX-ES-001-NORMEX-2005 show that this technology could be able to supply stable temperatures for industrial processes. However, a new prototype is going to be developed and constructed in order to improve some manufacturing errors detected in these experimental tests.

Soiling and other optical losses in solar‐tracking PV plants in navarra

AbstractField data of soiling energy losses on PV plants are scarce. Furthermore, since dirt type and accumulation vary with the location characteristics (climate, surroundings, etc.), the available data on optical losses are, necessarily, site dependent. This paper presents field measurements of dirt energy losses (dust) and irradiance incidence angle losses along 2005 on a solar‐tracking PV plant located south of Navarre (Spain). The paper proposes a method to calculate these losses based on the difference between irradiance measured by calibrated cells on several trackers of the PV plant and irradiance calculated from measurements by two pyranometers (one of them incorporating a shadow ring) regularly cleaned. The equivalent optical energy losses of an installation incorporating fixed horizontal modules at the same location have been calculated as well. The effect of dirt on both types of installations will accordingly be compared. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Potential of Polygeneration With Solar Thermal and Photovoltaic Systems

The efficiency of both solar thermal and photovoltaic (PV) systems for power generation is usually in the range of 10–30%, meaning that more than two-thirds of the collected radiation energy is lost. Cogeneration, or more generally polygeneration, means capturing and using some of the wasted energy and therefore increasing the overall efficiency of the solar conversion. Several paths of solar polygeneration are investigated: both thermal and photovoltaic receivers, with use of the waste heat to generate additional electricity by a heat engine, a direct use as heat, and use of the waste heat to operate a thermal process (absorption cooling). Appropriate optical and thermal energy losses are taken into account in all cases. The receiver temperature and the sunlight concentration level serve as free parameters. It is shown that concentrating the solar radiation is essential to effective polygeneration, and that there is an optimal operating temperature for each system. Polygeneration leads to increased conversion efficiency in all cases, and the scenarios based on PV show better results than those based on thermal converters. Scenarios showing electricity replacement up to 43% (normalized to the incident radiation) are presented.

Analysis of Potential Conversion Efficiency of a Solar Hybrid System With High-Temperature Stage

The analysis is given of hybrid system of solar energy conversion having a stage operating at high temperature. The system contains a radiation concentrator, a photovoltaic solar cell, and a thermal generator, which could be thermoelectric one or a heat engine. Two options are discussed, one (a) with concentration of the whole solar radiation on the PV cell working at high temperature and coupled to the high-temperature stage, and another (b) with a special PV cell construction, which allows the use of the part of solar spectrum not absorbed in the semiconductor material of the cell (“thermal energy”) to drive the high-temperature stage while the cell is working at ambient temperature. The possibilities of using different semiconductor materials are analyzed. It is shown that the demands to the cell material are different in the two cases examined: in system (a) with high temperature of cell operation, the materials providing minimum temperature dependence of the conversion efficiency are necessary, for another system (b) the materials with the larger band gap are profitable. The efficiency of thermal generator is assumed to be proportional to that of the Carnot engine. The optical and thermal energy losses are taken into account, including the losses by convection and radiation in the high-temperature stage. The radiation losses impose restrictions upon the working temperature of the thermal generator in the system (b), thus defining the highest possible concentration ratio. The calculations made show that the hybrid system proposed could be both efficient and practical, promising the total conversion efficiency around 25-30% for system (a), and 30-40% for system (b).

Scattering of light in polymer waveguides

An investigation was made of the scattering properties of polymer optical fibers with the aim of identification of the mechanism responsible for the optical energy losses. An analysis was made of the methods for determination of light scattering involving different ways of averaging over the length of a polymer optical fiber and the theory of the methods was considered. It was found that quantitative estimates could be obtained of the size of scattering inhomogeneities from the experimentally determined wavelength dependences of the scattering factor. The size of the scattering inhomogeneities in polymer optical fibers with a polystyrene core was found to be in the range 30–200 nm, in good agreement with the results of electron-microscopic investigations of the structure of the same samples.

Sur l'anisotropie des pertes d'energie et des constantes optiques du graphite dans l'ultraviolet

With the help of a single dielectric constant model, it is possible (following Tosatti and Bassani's explanation) to illustrate anisotropy of optical constants and electron energy losses on graphite.

Optical Transmissivity and Characteristic Energy Losses*

Optical Transmissivity and Characteristic Energy Losses*