Optimal Conversion Efficiency Research Articles

In-situ deposition of tungsten oxide hole-contact by Hot-Wire CVD and its application in dopant-free heterojunction solar cells

The tungsten oxide (WO x ) thin films have been deposited by a novel hot filament oxidation-sublimation process and applied in the dopant-free heterojunction solar cells as the hole selective contacts. The oxygen flow ratio plays a significant role during the deposition process. With increasing the oxygen flow ratio from 1.7% to 6.7%, the morphology of WO x films changes from small cauliflower-like particles to large cluster accumulation, and the ratio of W6+ increases from 76.1% to 91.4% with the ratio of W5+ decreasing from 23.9% to 8.6%. The work function of WO x can be tailored in a range of 5.5–6.1 eV by increasing the oxygen flow ratio. Its optical band gap maintains above 3.2 eV with the conductivity of about 10−5 S·cm−1. We have applied the WO x films in dopant-free silicon heterojunction solar cells as the hole selective contact layer by replacing the p-type amorphous silicon layer. By taking advantage of the highly transparent WO x layer, a high photon-current density of 39.6 mA·cm−2 was achieved with the oxygen flow ratio of 1.7%. It is interesting to find that the optimum cell conversion efficiencies of 14.9% were obtained with the oxygen flow ratio of 1.7% and the thickness of 10–20 nm for the deposition of WO x layer. This work proves the feasibility and good potential of Hot-Wire CVD prepared WO x hole selective contact for efficient dopant-free silicon heterojunction solar cells.

Widely Tunable Single-Photon Frequency Conversion in a Nanomechanically Reconfigurable Si-Rich Nitride Waveguide

An on-demand single-photon source based on self-assembled semiconductor quantum dots (QDs) is a key building block for quantum communication and quantum information processing. To scale up, a challenge lies in frequency converting the emitted photons to the telecom wavelengths and eliminating the wavelength difference between multiple QDs. In this paper, we propose a novel nanomechanical silicon-rich nitride waveguide device, which can be reconfigured to realize efficient frequency conversion from the emission wavelength band of InAs/GaAs quantum dots at 900 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula> 950 nm to the telecom C-band around 1550 nm, by exploiting the Bragg scattering process in nonlinear four-wave mixing. Numerical results show that an optimal conversion efficiency over 99% and a signal-to-noise ratio up to 27 dB can be achieved when the waveguide loss is negligible, and the efficiency only reduces to 78% when a realistic loss of 1 dB/cm is considered. We conduct a detailed study on the unwanted noise processes, and provide design guidelines to improve the conversion efficiency and suppress the noises, e.g., by optimizing the power and wavelength of the pump laser.

Performance improvement approach of all inorganic perovskite solar cell with numerical simulation

Lead-halide perovskites (PVKs) based solar cells have seen remarkable consideration due to improved efficiency, ease of fabrication, versatility and flexibility. However, the existence of lead, a toxic material, raises several concerns about the environment and the health of living beings and hinders their future commercialization. Therefore, a considerable surge in searching for an alternate lead-free PVK has started in the past few years. Several lead-free PVK solar cells have been proposed; nonetheless, achievable conversion efficiency from these devices is not up to the mark due to some inherent losses. Therefore, a comprehensive theoretical analysis is needed to understand the root of these losses for uplifting efficiency. Thus, the results of a specific modelling technique for all-inorganic lead-free PVK-based solar cells, namely cesium tin germanium halide (CsSnGeI3), to achieve the highest feasible efficiencies. The current simulation uses an electron transport material (ETM) of TiO2 and a hole transport material (HTM) of Spiro-OMeTAD to sandwich PVK layers of CsSnGeI3 (Eg=1.5 eV) for the PSCs. The device is subjected to further analysis and optimization of active layer thickness, defect density, operating temperature, defect density, capacitance-voltage (C-V) and impedance analysis to investigate the different performance parameters. The optimized conversion efficiency of 28.4% has been achieved with CsSnGeI3-based PSC. Results reported in this study may pave the way to developing lead-free PVK solar cells through higher conversion efficiencies.

The study of AgInS2 solar cell using simulation software wxAMPS

In this paper, wxAMPS software is used to simulate the performances of AgInS2 (AIS) based solar cell. Simulation results show that most suitable buffer layer is ZnS with thickness of 50 nm.Then, the parameters, such as thickness of absorption layer, carrier concentration and temperature, are simulated to study the effects on the performances of solar cells. When thickness and carrier concentration of absorption layer are 1000 nm and 1 × 1016 cm−3, respectively, excellent performances of AIS solar cell are received. Furthermore, temperature has a negative effect on solar cell performances. Finally, the effects of back surface field (BSF) layers (ZnTe and MoSe2) on solar cell performances are simulated and analyzed. AIS solar cell with MoSe2 layer obtains optimal photoelectric conversion efficiency (η) of 18.9964% with open-circuit voltage (Voc) of 0.9063 V, short-circuit current density (Jsc) of 36.3084 mA/cm2 and fill factor (FF) of 57.7278%.

Design of a microwave power transmission demonstration system for space solar power station

A microwave power transmission (MPT) demonstration system was assembled to comprehensively emulate the operating mode of MPT in space solar power station (SSPS). Based on solid power amplifier and phased antenna array, this system comprised three main parts, that is, microwave power transmitting subsystem, microwave power rectenna subsystem, and power beam steering subsystem. It was employed to validate the constraint relationship between beam collection efficiency and the sizes of transmitting antenna and rectenna, transmission distance, operation frequency. High efficiency rectifying and accurate beam steering were also demonstrated. The power transmitting antenna was composed of 64 sub-arrays of patch antennas, with the dimension of 1.2 × 1.2 m2. In addition, the rectenna array was constructed as a corner truncated square with the side length of 2 m. Its design was based on the concept of perfectly matched layer and integrated rectifying surface. The power beam steering subsystem, implemented with software retrodirective idea, pointed the microwave beam to the rectenna according to the direction of arrival of the pilot signal. The experimental MPT system, operating at 5.8 GHz, transmitted 910 W microwave power across 30 m distance. At the power receiving end, the optimum rectenna conversion efficiency of 49.3% was obtained. With aid of the beam steering subsystem, beam granularity, and beam steering accuracy of 0.23 and 0.18° were achieved, respectively. The compositive experiment verified all function as power transmitting, receiving, rectifying, and steering of MPT system. MPT technology is thus driven toward engineering application, and will ultimately space solar power exploration.

Efficient and stable heterostructured Co9S8/Cu7S4 composite counter electrodes derived from Prussian blue analogs for quantum dot-sensitized solar cells

The challenge of boosting the efficiency of QDSSCs lies in the rational development and design of economical, stable and efficient counter electrode (CE) catalysts for fast and efficient electron transport at the CE/electrolyte interface. Here, we creatively construct Co9S8/Cu7S4 heterostructure composite CEs using CuCo-Prussian blue analogs (PBA) as precursor by one-step in-situ solvothermal vulcanization method. Work function analysis and systematic electrochemical characterizations reveal that the presence of heterojunctions in the Co9S8/Cu7S4 can increase the interfacial electric field driving force inside the material, thereby reducing the Rct at CE/electrolyte interface, promoting the efficient transfer of electrons. Correspondingly, the Co9S8/Cu7S4 composite CE can improve the stability and compensate for the deficiency of the single component CE through a decent synergistic catalytic effect. Remarkably, the Mn-CdS/CdSe/ZnS co-sensitized QDSSC equipped with Co9S8/Cu7S4 heterostructure composite CE delivers an optimal conversion efficiency of 8.43% with Jsc = 23.42 mA/cm2, Voc = 0.672 V; FF = 0.54, which was significantly superior to physically mixed CE (PM-Co9S8/Cu7S4, 6.55%), single-component CE (Cu7S4, 5.60%; Co9S8, 5.13%) and conventional Brass/Cu2S CE (4.96%). In briefly, the advanced heterostructure engineering and the abundant, tunable chemical elemental composition of PBA provide new views for the purposeful design of economical and outstanding heterostructured composite CEs.

Effect of TeO2 on Ag/Si interface contact of crystalline silicon solar cells

• The effects of TeO 2 on the sintering of c-Si solar cell are systematically studied. • TeO 2 affects the morphology of the grids on the sintering process of Ag pastes. • TeO 2 promotes Ag pastes sintering and improves the conductivity of Ag grids. • TeO 2 promotes the growth of the Ag nanocrystallites in Ag/Si contact interface. • An optimal conversion efficiency of solar cells was acquired at TeO 2 content ∼40%. Glass frits, as a critical ingredient, plays an important role between Ag electrode and crystalline silicon (c-Si) solar cells and determines sintering properties of the silver paste and contact quality with c-Si solar cells. Here glass frits with different contents of TeO 2 are prepared and used to investigate the sintering process and effects of contact quality of Ag pastes on c-Si solar cells. Microstructures and electrical properties of the Ag/Si contact interface and performances of the resultant c-Si solar cells are characterized systematically. The results show that TeO 2 promotes the growth of Ag nanocrystallites in the glass layer between Ag grids and c-Si wafers, thus reduces the contact resistance of the Ag grids and improves the contact quality of the Ag/Si interfaces. Moreover, TeO 2 improves the densification and conductive performances of the Ag grids. However, excessive TeO 2 has a negative effect on the conductivity of the Ag grid due to the increased thickness of the glass layer. Based on the competing factors played by TeO 2 , the conversion efficiency is the highest at an optimized TeO 2 content ∼40%.

Towards optimal conversion efficiency of Brillouin random fiber lasers in a half-open linear cavity.

We proposed and demonstrated an unprecedented high-efficiency Brillouin random fiber laser (BRFL) by fiber length optimization in a half-open linear cavity. In terms of the trade-off between Brillouin gain saturation and weak distributed Rayleigh feedback strength, optimal laser efficiency associated to proper fiber length in a BRFL was theoretically predicted. As a proof-of-concept, a unidirectional-pumped BRFL with a half-open linear cavity was experimentally conducted, in which a fiber Bragg grating at one end of gain fiber served as a high-reflection mirror while Rayleigh scattering enabled distributed feedback for random lasing resonance. Results show that the optimal fiber length of ∼3.4 km in the BRFL offers sufficient Rayleigh scattered random feedback whilst alleviating the Brillouin gain saturation to a large extent. Consequently, an optimal laser efficiency of 77.0% in the BRFL was experimentally demonstrated, which reaches the state-of-the-art high record. Laser characteristics, including the linewidth, statistics and frequency jitter were also systematically investigated. It is believed that such efficient BRFL could provide a promising platform for inspiring new explorations of laser physics as well as potentials in long-haul coherent communication and fiber-optic sensing.

Three-Dimensional Artificial Transpiration Structure Based on 1T/2H-MoS2/Activated Carbon Fiber Cloth for Solar Steam Generation.

The rise of solar steam generation is an effective strategy to mitigate clean water shortages. However, achieving further improvements in conversion efficiency and stability remains a challenge. Here, 1T/2H-MoS2 nanosheets were uniformly assembled on activated carbon fiber cloth (A-CFC) through a facial hydrothermal method, and a three-dimensional (3D)-artificial transpiration device (ATD) was prepared using the plant transpiration process. The combination of activated carbon fiber cloth and 1T/2H phase MoS2 exhibits high light absorption (∼97.5%), excellent mechanical stability, large evaporation area, and easy escape of vapor. Additionally, the 3D hollow cone of the MoS2/carbon fiber cloth can effectively reduce radiative and convective energy loss and then achieve the enhancement of energy collection from the environment. An outstanding evaporation rate of 1.61 kg·m-2·h-1 with an optimum conversion efficiency of 97% under one sun is reached. Based on the facile fabrication, excellent stability, and high solar conversion efficiency, this nature-inspired design of 3D 1T/2H-MoS2/A-CFC is expected to facilitate large-scale applications for seawater purification and desalination.

Blade-resolved numerical simulations of the NREL offshore 5 MW baseline wind turbine in full scale: A study of proper solver configuration and discretization strategies

This paper presents a blade-resolved numerical investigation of the NREL 5 MW baseline wind turbine for offshore applications including blade-tower interference, analyzing the solver configuration and its influence on the results accuracy and computational costs. The wind turbine was analyzed considering its full dimensions under the operating condition of optimal wind-power conversion efficiency for a wind speed of 10 m/s at hub height. The power production, generated thrust, and forces distribution along the blade span were estimated. The computational analyses were carried out using a Computational Fluid Dynamics (CFD) methodology employing the Finite Volume Method (FVM) implemented in the OpenFOAM software considering different approaches of the Pressure Implicit Split Operator (PISO) solver and different mesh refinement strategies for the spatial discretization process, which resulted in two different meshes being investigated. For one of the meshes, a temporal discretization analysis was performed for three different CFL numbers. The iterative form of the PISO algorithm was considered in its generic form and with an extra step to correct the pressure before the beginning of the iterative process in each time step. Both approaches can be accomplished in OpenFOAM through the PIMPLE solver facilities for the treatment of the pressure-velocity coupling in unsteady problems. The analysis of the transient incompressible turbulent flow was conducted considering the same turbulence model for all CFD investigations, the URANS k − ω SST. A numerical verification was conducted in each analysis by comparing the CFD results against values obtained using the blade element momentum theory, implemented in OpenFAST. To conclude each analysis, a computational cost investigation was carried out. Finally, for the spatial and temporal discretization investigation, detailed information regarding the flow characteristics is presented. According to the accuracy of the results obtained through the CFD simulations, the best numerical arrangement is given by the iterative PISO with face flux correction as pressure-based solver and a temporal discretization which employs lower values of CFL, such as 1 or 2.

Snowflake-Like Cu2S/MoS2/Pt heterostructure with near infrared photothermal-enhanced electrocatalytic and photoelectrocatalytic hydrogen production

Snowflake-like Cu2S/MoS2 heterostructures with varied compositions were constructed via a two-step hydrothermal method. The 45-Cu2S/MoS2 with 45 wt% Cu2S was found as the optimum catalyst, which displayed photothermal enhanced hydrogen evolution reaction (HER) performance under near infrared (NIR) irradiation. After electrochemical deposition of a tiny amount of Pt (45-Cu2S/MoS2/Pt-100s), Schottky barrier was formed between Pt nanoparticles and MoS2 nanosheets. Using 45-Cu2S/MoS2/Pt-100s as an electrocatalyst, low overpotential of 78 mV (@10 mV cm−2) and Tafel slope of 48 mV dec−1 were achieved with the assistance of NIR irradiation. The photoelectrochemical (PEC) hydrogen production performance of 45-Cu2S/MoS2/Pt-100s was also investigated. The optimal conversion efficiency of 45-Cu2S/MoS2/Pt-100s could reach 0.78% at 0.57 V (vs. reversible hydrogen electrode (RHE)). The control of the internal geometric and electronic structure of the catalysts and the aid of photothermal effect in this work provide new ideas for designing high-efficiency hydrogen evolution catalysts.

Mn-doped Ca2Fe2O5 oxygen carrier for chemical looping gasification of biogas residue: Effect of oxygen uncoupling

Anaerobic digestion is an important approach to treat and utilize kitchen waste, while kitchen waste derived biogas residue (BR) disposal remains a serious problem in this process. This study investigated the feasibility of chemical looping gasification (CLG) as an efficient way to treat and generate syngas from BR. Besides, Mn-doped Ca2Fe2O5 (MCF) as a novel oxygen carrier with mild oxygen uncoupling capability was developed, and its performance against traditional Ca2Fe2O5 (CF) oxygen carrier was compared. Results indicated that, significant oxygen release capability was observed on the prepared MCF oxygen carrier. In the gasification tests, CLG with MCF at 800 ℃ showed optimal total gas yield, carbon conversion, and cold gas efficiency, which increased 0.08 Nm3/kg, 17.22%, and 13.37% compared to CF, respectively. According to the XPS, H2-TPR and XRD characterization results, the optimal performance of MCF could be attributed to the oxygen uncoupling characteristic brought by Mn addition. The formation of the oxygen uncoupling capability of MCF could be explained by three reasons: (1) Mn in MCF mainly existed in form of Mn3+ and Mn4+, which resulted in the extremely strong oxidability at a temperature as low as 250 ℃. (2) The higher Fe3+/Fe2+ ratio of 1.55 in MCF than CF caused by Mn addition led to greater oxidability of Fe ions. (3) MCF had a higher lattice oxygen amount than CF at about 3.86%, and the lattice oxygen in its crystal structure had been transformed into active lattice oxygen species, which were between lattice oxygen (O2–) and atomic adsorbed oxygen (O−). As a result, this paper investigated the potential of CLG to treat and utilized BR, and the superiority of CLG with oxygen uncoupling (CLGOU) on MCF was highlighted. It’s hoped that this study could provide a fundamental knowledge on CLG and CLGOU of BR, and benefit to better downstream process design of anaerobic digestion industry.

Electroreduction of air-level CO2 with high conversion efficiency

The electrochemical conversion of carbon dioxide (CO 2 ) has been attracting increasingly research interest in the past decade, with the ultimate goal of utilizing electricity from renewable energy to realize carbon neutrality, as well as economic and energy benefits. Nonetheless, the capture and concentrating of CO 2 cost a substantial portion of energy, while almost all the reported researches showed CO 2 electroreduction under high concentrations of (typically pure) CO 2 reactants, and only very few recent studies have investigated the capability of applying low CO 2 concentrations (such as ~10% in flue gases). In this work, we first demonstrated the electroreduction of 0.03% CO 2 (in helium) in a homemade gas-phase electrochemical electrolyzer, using a low-cost copper (Cu) or nanoscale copper (nano-Cu) catalyst. Mixed with steam, the gas-phase CO 2 was directly delivered onto the gas-solid interface with the Cu catalyst and reduced to CO, without the need/constraint of being adsorbed by aqueous solution or alkaline electrolytes. By tuning the catalyst and experimental parameters, the conversion efficiency of CO 2 reached as high as ~95%. Furthermore, we demonstrated the direct electroreduction of 0.04% CO 2 from real air sample with an optimized conversion efficiency of ~79%, suggesting a promising perspective of the electroreduction approach toward direct CO 2 conversion. This paper realizes the direct electroreduction of 0.03% or 0.04% CO 2 in a homemade gas-phase electrochemical reactor using a low-cost copper (Cu) or nanoscale copper (nano-Cu) catalyst with high CO 2 conversion efficiency.

Double POLO Carrier Selective Contact Based PERC Solar Cell for 25.5% Conversion Efficiency: A Simulation Study

Polycrystalline Silicon on Oxide (POLO) passivating contacts have emerged as a carrier selective contact for high-efficiency Si-based photovoltaic (PV) devices. In this paper, double POLO PERC (Passivated Emitter and Rear Contact) device is designed by employing POLO contacts on both contact sides to reduce the contact recombination losses through Silvaco-TCAD tool. The performance of the double POLO PERC device has been studied by using the PV parameters and current-density (J-V) curve. The impact of tunnel oxide thickness variation (1 nm, 1.25 nm, 1.5 nm) in the tunnel oxide layer is also analyzed. The performance of textured double POLO PERC solar cell is optimized at 1.5 nm thickness (TOX), which reflects optimum conversion efficiency of 25.5%. Reported study of double POLO PERC device may open up a door for further improvement in PERC device performance.

Optimization of Biodiesel Production Parameters from Cucurbita maxima Waste Oil Using Microwave Assisted via Box-Behnken Design Approach

The production of biodiesel from vegetables or fruits waste oils has high potential as renewable energy. The Cucurbita maxima wastes are massive source of oils, which are believed to indicate the possible sources of renewable energy whose biodiesel can be produced. Hence, the study explores the potential of the Cucurbita maxima wastes, for the production of biodiesel. In this study, the Soxhlet extraction method was used to extract Cucurbita maxima waste oil using an organic solvent. Through Box-Behnken design (BBD), the effects of methanol to oil molar ratio (6–10), catalyst concentration (2–6%), and reaction time (45–75 min) on the transesterification efficiency of methyl esters were investigated. The oil contents of Cucurbita maxima waste was found to be 44.6 ± 0.21 %. This oil was characterized, and after obtaining the pure characterized oil, biodiesel was produced using microwave assisted by the transesterification process. The optimum conversion efficiency of the Cucurbita maxima waste oil to fatty acid methyl ether was 97.76%, at the optimal parameters, methanol to oil ratio (8.4 : 1), catalyst concentration (3.14%), and reaction time (57.12 min). The results revealed that all parameters have a significant effect on the yield of biodiesel ( p &lt; 0.0001 ). The physicochemical properties reveal that the Cucurbita maxima waste oil could be applied as a potential source of material for methyl ester production. The fatty acid profile of the oil indicated that it was mainly composed of unsaturated fatty acid, which ensures good flow properties of the fuel. The results of these studies showed the prospective of Cucurbita maxima wastes as a new potential feedstock for biodiesel production.

Enhancement of the second harmonic generation from monolayer WS2 coupled with a silica microsphere

Monolayer transition metal dichalcogenides (TMDs) are widely used for integrated optical and photoelectric devices. Owing to their broken inversion symmetry, monolayer TMDs have a large second-order optical nonlinearity. However, the optical second-order nonlinear conversion efficiency of monolayer TMDs is still limited by the interaction length. In this work, we theoretically study the second harmonic generation (SHG) from monolayer tungsten sulfide (WS2) enhanced by a silica microsphere cavity. By tuning the position, size, and crystal orientation of the material, second-order nonlinear coupling can occur between the fundamental pump mode and different second harmonic cavity modes, and we obtain an optimal SHG conversion efficiency with orders of magnitude enhancement. Our work demonstrates that the microsphere cavity can significantly enhance SHG from monolayer 2D materials under flexible conditions.

Environmental‐Friendly Polymer for Efficient and Stable Inverted Perovskite Solar Cells with Mitigating Lead Leakage

AbstractAlthough perovskite solar cells (PSCs) are on the road to industrialization, the operational stability under high efficiency still needs to be improved, and the water solubility of lead ions (Pb2+) will cause environmental pollution problems. Herein, it is successfully implanted an environment‐friendly (biodegradability) poly(butylene adipate‐coterephthalate) polymer (PBAT) into the perovskite film, which can passivate the uncoordinated Pb2+ and neutral iodine defects of the perovskite material because of the adequate carbonyl groups and benzene rings in PBAT polymer, thereby regulating the crystallization of perovskite film with lower trap density, inhibiting the nonradiative recombination and improving charge carrier transport. As a result, the polymer‐incorporated inverted PSCs achieve optimal conversion efficiencies of 22.07% (0.1 cm2) and 20.31% (1 cm2). Meanwhile, the incorporated device, after being encapsulated, exhibits a prominent improvement in operational stability of high‐efficiency device under maximum power point tracking and continuous one sunlight illumination, maintaining the initial efficiency of 80% for 3249 h. More importantly, the polymer network can protect Pb2+ from being dissolved by water and prevent nearly 98% of Pb2+ from leaking by directly immersing the polymer‐coated perovskite film in water. Environmental‐friendly molecules provide new hope for solving lead poisoning and improving device operational stability under high efficiency.

Theoretical calculation and particle-in-cell simulation of a multi-mode relativistic backward wave oscillator operating at low magnetic field

Increasing the dimensions of high power microwave devices is an efficient method to improve the power capacity. However, an overmoded structure usually results in mode competition and a low beam-wave conversion efficiency. In this paper, a multi-mode operation mechanism is used to avoid mode competition and increase the efficiency. The calculation results of nonlinear theory of beam-multimode interaction show that the optimized conversion efficiency is up to 48% when TM01 mode, TM02 mode, and TM03 mode are all considered. As only the TM01 mode, TM02 mode, or TM03 mode is taken into account independently, the corresponding efficiency is 38%, 22%, or 20%. Based on this, a multi-mode relativistic backward wave oscillator is proposed with the ratio of the mean diameter of the slow wave structure (SWS) to the wavelength of the output microwave to be 3.5. The non-uniform SWS is used to increase the beam-wave conversion efficiency, and a combined reflector is adopted to reflect partial of the mixed microwave modes and make the device compact. The particle-in-cell simulations show that as the diode voltage is 1.1 MV, the beam current is 22.8 kA, and the external magnetic field is 0.76 T, the conversion efficiency is 45%, and the output microwave of 11.3 GW is the mixed modes of TM01 mode, TM02 mode, and TM03 modes with the corresponding power ratio of 74%, 7%, and 19%, respectively.

Hierarchical microencapsulation of phase change material with carbon-nanotubes/polydopamine/silica shell for synergistic enhancement of solar photothermal conversion and storage

Aiming at improving the utilization efficiency of solar photothermal energy, this study focuses on a novel phase-change microcapsule system based on an n-docosane core and a carbon-nanotubes (CNTs)/polydopamine (PDA)/silica hierarchical shell. The system was fabricated by encapsulating n-docosane in a silica shell and then depositing a PDA layer on the shell surface, followed by conglutinating CNTs onto the PDA layer. The resultant microcapsule system shows a regular spherical morphology together with desired core-shell hierarchical microstructure and chemical compositions. The presence of CNTs/PDA coating layer can impart an efficient solar light-to-heat energy conversion capability to the microcapsule system through photon capture and sunlight absorption. The microcapsule system not only shows a good latent heat-storage capability with satisfactory phase-change enthalpies of over 130 J/g but also exhibits an optimal photothermal conversion efficiency of 90.1%. The microcapsule system also exhibits good leakage-prevention performance, high thermal cycle stability, excellent thermal impact resistance, and good shape/form stability to deal with a wide range of solar photothermal energy applications. Through integrating CNTs and PDA into a phase-change microcapsule system, this work provides a promising approach for the development of PCMs-based functional materials with enhanced solar light-to-heat energy conversion and storage performance for efficient utilization of solar energy.

Simultaneously Achieving Circular‐To‐Linear Polarization Conversion and Electromagnetically Induced Transparency by Utilizing a Metasurface

AbstractIn this work, the simultaneous realization of circular‐to‐linear polarization conversion (PC) and electromagnetically induced transparency (EIT) is theoretically reported in terahertz (THz) range by utilizing a metasurface when left‐handed circularly polarized (LCP) waves are incident. The metasurface is composed of two kinds of via‐coupled modules (VCMs). Each module can realize the same EIT phenomenon by the destructive interference during the bright and dark modes due to the symmetry‐broken rotation operation of the structure instead of the near‐field coupling. The VCMs can simultaneously respond to the incident LCP waves and are identically converted into LCP and right‐handed circularly polarized (RCP) waves, which own the same amplitudes and phase shifts. Therefore, the LCP and RCP waves can generate a resultant linearly polarized (LP) wave. The EIT transparent windows have emerged in 0.729–1.051 THz during the transmission of the LCP waves and the conversion of LCP to RCP. The values of maximum group delays both are 358 ps. The operating frequency band of the PC is located in 0.65–1.10 THz, and relative bandwidth reaches 51.4%. Optimal relative conversion efficiency reaches 93.2% at 0.921 THz. The EIT behavior has been investigated by the two‐oscillator model to further confirm the consistency of the simulation results.