Metasurface holograms reaching 80% efficiency.

Solar Cell Capacitance Simulator in 1 Dimension (SCAPS-1D) is used to investigate the possibility of realizing ultrathin CdTe based solar cells with high and stable conversion efficiency. In the first step, we modified the conventional cell structure by substituting the CdS window layer with a CdS:O film having a wide band gap ranging from 2.42 to 3.17 eV. Thereafter, we simulated the quantum efficiency, as well as the parameters ofJ-Vcharacteristics, and showed how the thickness of CdS:O layer influences output parameters of Glass/SnO2/ZTO/CdS:O/CdTe1-xSx/CdTe/Ni reference cell. High conversion efficiency of 17.30% has been found using CdTe1-xSx(x=0.12) and CdTe layers of thickness 15 nm and 4 μm, respectively. Secondly, we introduced a BSR layer between the absorber layer and back metal contact, which led to Glass/SnO2/ZTO/CdS:O/CdTe1-xSx/CdTe/BSR/Ni configuration. We found that a few nanometers (about 5 nm) of CdTe1-xSxlayer is sufficient to obtain high conversion efficiency. For BSR layer, different materials with large band gap, such as ZnTe, Cu2Te, and p+-CdTe, have been used in order to reduce minority carrier recombination at the back contact. When ZnTe is used, high conversion efficiency of 21.65% and better stability are obtained, compared to other BSR.

In this paper, a uniform nanorod (NR) array is etched onto the surface of Micro‐Light‐Emitting‐Diodes (µLEDs) and mix Ag nanoparticles (NPs) with QDs to fill the gaps between the nanorods. Simultaneously, the study utilizes graphene to connect individual nanorods and enhance current spreading. The nanorod array's structure significantly reduces the distance between the QDs and the quantum well (QW), reducing energy loss from the excitation light source through a non‐radiative energy transfer (NRET) mechanism. Additionally, the Ag NPs function as localized surface plasmons (LSPs), further enhancing the CCE of QDs via the absorption resonance. In this study, the effects of two types of Ag NPs are compared with different absorption resonance peaks on device performance. The results demonstrate that Ag NPs with absorption resonance peaks matching the emission wavelength of QDs play a more crucial role in the system. This configuration achieves a CCE of 77.78% for µLEDs with nanorod arrays, operating at a current of 10 mA. Compared to the conventional µLED structure with QDs only on the surface, the proposed method improves the CCE of µLEDs by an impressive 86.5%. This outcome underscores the significant contribution of the NR structure and LSPs in enhancing the CCE of QD‐µLEDs.

Dye-sensitized solar cells (DSSCs) have aroused intense interest and been regarded as one of the most prospective solar cells, due to low-cost, flexibility, simple device fabrication and high conversion efficiency under weak light, in comparison to the conventional photovoltaic devices. Very recently, G2E in Swiss and G24i in UK including Korean and Japan companies have demonstrated commercial and prototyped components based on DSSC technology with liquid electrolytes. However, the unit costs, long-term device stability and power conversion efficiency must be further improved for real-life applications. For this purpose, considerable efforts have been devoted to the search for low cost Pt-free catalysts that exhibit high electrochemical activity and fast electron transfer kinetics, while a platinum (Pt) catalyst is still the most efficient and widely used counter electrode (CE) in DSSCs, but it has some problems that make it unsatisfactory, such as its high manufacturing cost, due to scarcity, and poor long-term stability for the iodide/triiodide redox couple in a DSSC. As a result, significant efforts have been devoted to finding possible alternatives to Pt, including carbon blacks, carbon nanotubes, functionalized graphene, and heteroatom-doped GnPs as efficient metal-free electrocatalysts. One of the most promising candidates as CE materials is non-metallic heteroatom-doped graphene nanoplatelets (GnPs). Heteroatom-doped GnPs gave high power conversion efficiency (PCE) of DSSCs employing cobalt electrolytes. However, they are not sufficiently active in iodidde electrolytes, which are more common and desirable electrolytes. Thus, the better elcetrocatalytical ability and electrochemical stability of carbon-basedmaterials toward the redox couples still need to be significantly improved for the practical applicationof DSSCs. Very recently, a series of edge-fuctionalized heteroatom-doped and metalliod-doped graphene nanoplatelets (GnPs) have been prepared through a simple mechanochemical ball-milling process. In this presentation, comparative study of edge-functionalized heteroatom-doped and metalloid-doped graphene nanoplatelets as metal-free counter electrodes for highly efficient dye-sensitized solar cells employong bothe redox shuttles will be described to understand and establish the structure-property relationship between sort of fuctionalization and cell performance with regard to the present GnPs through the same fabrication process under the same experimental condition.

Fabrication of bilayered attapulgite for solar steam generation with high conversion efficiency

A novel pyrene-imidazole derivative (PyPI), which can form effcient π-π stacking in solid film, has been utilized in organic solar cells (OSCs). The stacking of small a molecule PyPI can facilitate a charge transfer and suppress fullerene aggregation. As a result, PTB7-Th: PyPI: PC71BM based ternary OSC exhibits a high power conversion efficiency (PCE) of 10.36%, which presents a 15.88% increase from the binary device (8.94%). Concurrently, the ternary OSC shows a much better thermal and light illumination stability. Under continuous 60°C annealing for 3 h, in atmosphere, the device still remains at 94.13% efficiency more than the pristine state, while the control device remains at 52.47% PCE. Constant illumination under Air Mass (AM) 1.5G irradiation (100 mW cm−2) in atmosphere, the PCE of OSC remains at 72.50%. The high conversion efficiency and excellent environmental stability of the PyPI based ternary OSC, has narrowed the gap between laboratory investigation and industrial production.

This paper presents a complete design methodology of a Class-E inverter for capacitive wireless power transfer (CWPT) applications, focusing on the capacitance coupling influence. The CWPT has been investigated in this paper, because most of the literature refers to inductive power transfer (IWPT). However, CWPT in perspective can result in lower cost and higher reliability than IWPT, because it does not need coils and related shields. The Class-E inverter has been selected, because it is a single switch inverter with a grounded MOSFET source terminal, and this leads to low costs and a simple control strategy. The presented design procedure ensures both zero voltage switching (ZVS) and zero derivative switching (ZDS) conditions at an optimum coupling coefficient, thus enabling a high transmission and conversion efficiency. The novelties of the proposed method are that the output power is boosted higher than in previous papers available in the literature, the inverter is operated at a high conversion efficiency, and the equivalent impedance of the capacitive wireless power transfer circuit to operate in resonance is exploited. The power and the efficiency have been increased by operating the inverter at 100 kHz so that turn-off losses, as well as losses in inductor and capacitors, are reduced. The closed-form expressions for all the Class-E inverter voltage and currents waveforms are derived, and this allows for the understanding of the effects of the coupling coefficient variations on ZVS and ZDS conditions. The analytical estimations are validated through several LTSpice simulations and experimental results. The converter circuit, used for the proposed analysis, has been designed and simulated, and a laboratory prototype has been experimentally tested. The experimental prototype can transfer 83.5 W at optimal capacitive coupling with operating at 100 kHz featuring 92.5% of the efficiency, confirming that theoretical and simulation results are in good agreement with the experimental tests.

In this paper, we propose a method to reconstruct frequency- and polarization-multiplexed terahertz (THz) holograms using an aperture-shared metalens composed of merely a single type of meta-atom structure. The focal points generated by the multi-foci metalens serve as the pixels of the holographic images. The designed meta-atom exhibits high circular polarization conversion efficiency at three frequencies; thus, the design of geometric phase metasurfaces can be implemented simultaneously at these three frequencies. A multi-foci metalens is designed using a phase multiplexing approach, with frequency multiplexing achieved through a shared aperture. Meanwhile, during the phase multiplexing design process, the edge phase profiles of different frequencies are adjusted to ensure that the focal spot sizes corresponding to different frequencies remain identical. Two design frequencies are selected for the reconstruction of final frequency-multiplexed holograms after accounting for the influence of dispersion. Additionally, amplitude coefficients are introduced into the phase profile design to mitigate the dispersive effects between different frequencies. Ultimately, through the simultaneous multiplexing of frequency and polarization, the reconstruction of holographic images with nearly uniform intensities across different frequencies is achieved after polarization detection. Our design method enables a single metasurface to simultaneously carry multiple images or pieces of information, which can enhance information density and, thus, holds application potential in fields such as THz communication, information storage, and encryption.

Superwetting monolithic hypercrosslinked polymers nanotubes with high salt-resistance for efficient solar steam generation

Oscillators based on Raman gain, known in the literature as Raman lasers, have until now necessitated an external optical pump. A powerful multi-watt fundamental laser radiation is usually required to offset a small value of the Raman gain coefficient, typically several 10-9cm/W in most Raman-active media. For example, these limitations in solid-state Raman lasers which employ scattering off a vibrational (phonon) resonance in a crystal or fiber have led to high thresholds and small conversion efficiencies. If these could be overcome such lasers would find important applications as compact light sources due to their spectral agility and could extend the range of semiconductor lasers. An important step in this direction was the recent demonstration of near infrared Raman lasers, in which ultralow threshold was achieved thanks to the use of high quality-factor dielectric microsphere resonators. Here we demonstrate a compact injection Raman laser operating in the mid-infrared, in which low threshold and high conversion efficiency are achieved by integrating within the active region of a quantum cascade region a Raman section designed to resonantly enhance the Raman gain by many orders of magnitude.

In this study, we show that the energy conversion efficiency in thermoelectric (TE) devices can be effectively improved through simultaneous optimization of carrier concentration, bandgap tuning, and fabrication of stepwise legs. n- and p-type Bi2Te3-based materials were selected as examples for testing the proposed approach. At first, the Boltzmann transport theory was employed to predict the optimal temperature-dependent carrier concentration for high thermoelectric performance over a broad temperature range. Then, the synthesized n-Bi2Te3-xSex and p-Bi2-xSbxTe3 solid solutions were tested to evaluate their suitability for fabricating the stepwise thermoelectric legs. The output energy characteristics of the designed TE devices were estimated using numerical modeling employing the finite element method. The theoretical simulation revealed an improvement in the conversion efficiency between the best homogeneous and stepwise TE legs from 8.8% to 10.1% and from 9.9% to 10.8% in p-type and n-type legs, respectively, which is much higher than the efficiency of the industrial thermoelectric modules (3-6%). The measured conversion efficiency of the fabricated n- and p-type stepwise legs reached very high values of 9.3% and 9.0%, respectively, at the relatively small temperature gradient of 375 K. This work suggests carrier concentration and bandgap engineering accompanied by the stepwise leg approach as powerful methods for achieving high energy conversion efficiency in thermoelectric converters.

Till date, fabrication of piezoelectric nanogenerator (PNG) with highly durable, high power density, and high energy conversion efficiency is of great concern. Here a flexible, sensitive, cost effective hybrid piezoelectric nanogenerator (HPNG) developed by integrating flexible steel woven fabric electrodes into poly(vinylidene fluoride) (PVDF)/aluminum oxides decorated reduced graphene oxide (AlO‐rGO) nanocomposite film is reported where AlO‐rGO acts as nucleating agent for electroactive β‐phase formation. The HPNG exhibits reliable energy harvesting performance with high output, fast charging capability, and high durability compared with previously reported PVDF based PNGs. This HPNG is capable for harvesting energy from a variety and easy accessible biomechanical and mechanical energy sources such as, body movements (e.g., hand folding, jogging, heel pressing, and foot striking, etc.) and machine vibration. The HPNG exhibits high output power density and energy conversion efficiency, facilitating direct light on different color of several commercial light‐emitting diodes instantly and powers up many portable electronic devices like wrist watch, calculator, speaker, and mobile liquid crystal display (LCD) screen through capacitor charging. More importantly, HPNG retains its performance after long compression cycles (≈158 400), demonstrating great promise as a piezoelectric energy harvester toward practical applications in harvesting biomechanical and mechanical energy for self‐powered systems.

In this paper, a dielectric-filled circular waveguide TM01-TE11 mode converter is proposed, which has high conversion efficiency and a wide operating bandwidth. Filling the circular waveguide with dielectric material changes the local propagation characteristics, thus achieving a phase difference between the TE11 modes in the two halves of the circular waveguide during propagation. This, in turn, facilitates the completion of mode conversion with high efficiency. Compared with the conventional radial dielectric plate, this paper improves the method of filling the dielectric inside the circular waveguide by transforming it into a coaxial structure. This is followed by the incorporation of a radial dielectric plate, a modification that has been proven to enhance the conversion efficiency and extend the operational bandwidth. The mode converter operates at 9.7 GHz, and when the dielectric filler material is polytetrafluoroethylene (PTFE), both simulation and practical studies are carried out. The simulation results demonstrate that the maximum conversion efficiency of this mode converter is 99.2%, and the bandwidth with conversion efficiency greater than 90% is nearly 21.1%. The maximum conversion efficiency in the actual test is essentially consistent with the simulation results. The validity of the design scheme of this converter and the accuracy of the simulation study are demonstrated.

Theoretical and experimental results on a 1-THz fiber frequency shifter with high conversion efficiency, pump and pump ASE cancellation, and rapid tunability for use in a wavelength division multiplexed communication network is presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Developing materials for efficient solar thermal energy conversion (STEC) is currently a promising field in energy research. Traditional STEC materials such as carbon and plasmonic nanomaterials have limited efficiency of solar heat utilization, despite their high photothermal conversion efficiency. This paper describes a film composed of hybrid nanofibers of a metal–organic framework layered on cellulose (MC film), resulting in both high photothermal conversion and heat utilization efficiency. The mechanically strong and flexible film can be designed as a solar-driven actuator, enabling large-angle actuation and high contractile power up to 2.5 times greater than that of human muscle. Furthermore, the gathered heat by a MC film-based apparatus can be manipulated to drive solar steam generation for highly efficient seawater desalination, generating clean water at rate of 2.25 kg m–2 h–1 under one-sun irradiation without surface salt accumulation. This work may provide a design rule for developing high-performance STEC systems.

Isotopic enrichment of diamond using microwave plasma-assisted chemical vapor deposition with high carbon conversion efficiency