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Artificial optic-neural synapse for colored and color-mixed pattern recognition
摘要： The priority of synaptic device researches has been given to prove the device potential for the emulation of synaptic dynamics and not to functionalize further synaptic devices for more complex learning. Here, we demonstrate an optic-neural synaptic device by implementing synaptic and optical-sensing functions together on h-BN/WSe2 heterostructure. This device mimics the colored and color-mixed pattern recognition capabilities of the human vision system when arranged in an optic-neural network. Our synaptic device demonstrates a close to linear weight update trajectory while providing a large number of stable conduction states with less than 1% variation per state. The device operates with low voltage spikes of 0.3 V and consumes only 66 fJ per spike. This consequently facilitates the demonstration of accurate and energy efficient colored and color-mixed pattern recognition. The work will be an important step toward neural networks that comprise neural sensing and training functions for more complex pattern recognition.
关键词： optic-neural synaptic device,human vision system,pattern recognition,energy efficiency,h-BN/WSe2 heterostructure
更新于2025-09-23 15:21:21
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Influence of the energy dependence of the absorption coefficient on the solar energy conversion efficiency
摘要： In most cases, when the ef?ciencies of a single or multi-gap (with intermediate bands) solar cell are evaluated, the energy dependence of the absorption coef?cients is ignored. In this work we will evaluate the range of optical thickness and average absorption coef?cients in which this dependence should be considered. For this study we use different absorption coef?cients generated randomly as a function of the energy. In many practical cases, the ef?ciencies are lower than those expected.
关键词： optical thickness,energy dependence,intermediate-band solar cells,solar energy conversion efficiency,absorption coefficient
更新于2025-09-23 15:21:21
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Si, N-codoped carbon dots: preparation and application in iron overload diagnosis
摘要： Heteroatom doping is a straightforward and smart strategy to improve the fluorescence efficiency of carbon dots (CDs). We synthesized the Si, N-codoped CDs (SiNCDs) with high quantum yield up to 29.7% through one-step hydrothermal method. The linear range for Fe3+ was between 0 and 200 μM, and the limit of detection was about 5 μM, which presented potential for Fe quantification in serum to diagnose Fe overload. In addition, the SiNCDs demonstrated good selectivity to Fe3+ among high concentrations of metal ions, amino acids and H2O2, so there is no need to mix additional reagents as the colorimetric method does in clinic, making SiNCDs more competitive in clinical application. Furthermore, we explored the practicability of SiNCDs by detecting Fe in serum from five healthy volunteers and three patients suffering Fe overload. The recovery rate was from 87.1 to 113.6%, which confirmed the application prospect of SiNCDs in clinical diagnostics.
关键词： N-codoped carbon dots,hydrothermal method,Si,iron overload diagnosis,fluorescence efficiency,quantum yield
更新于2025-09-23 15:21:21
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Characterization and application of cerium bromide spectrometers for analysis of γ-ray emitting radionuclides in food matrices
摘要： Cerium bromide (CeBr3) scintillators are useful room temperature gamma-ray detectors that provide the robustness of a scintillator with improved resolution over traditional sodium iodide (NaI) detectors. This makes them attractive for field deployment or emergency response operations especially when combined with the power of Monte-Carlo based efficiency determinations. This work documents the characterization of CeBr3 detectors and the efficiency determination of a portable CeBr3 detector based gamma-ray detection system for food measurements.
关键词： Gamma-ray measurement,Cerium bromide,Efficiency calculation,Food safety
更新于2025-09-23 15:21:21
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AIP Conference Proceedings [Author(s) SolarPACES 2017: International Conference on Concentrating Solar Power and Chemical Energy Systems - Santiago, Chile (26–29 September 2017)] - Design and performance analysis of volumetric solar receiver based on porous foam ceramics
摘要： Volumetric solar receiver is one of three main categories of solar receivers. It has great application prospect due to the simple structure, high thermal efficiency, and the air exit temperature can reach above more than 800℃. The porous material is used instead of tube as absorber in volumetric solar receiver to heat the working medium, and the incident radiation can be absorbed gradually from outside to inside. In this study, an one-dimensional volumetric solar receiver calculating model based on porous foam ceramics is constructed. The temperature distributions and radiation absorption efficiencies at different conditions are analyzed, and a kind of secondary heating volumetric solar receiver is put forward to further improve its thermal efficiency. The results show that both the outlet air temperature and the depth for the temperature of air and ceramic solid reaching to stability decreases apparently with decrease of porosity of ceramic foam, but the temperature of front surface of the receiver increases gradually. With decrease of porous ceramic diameter, the air exit temperature decreases gradually, and the depth for the temperature of air and ceramic solid reaching to stability is decreasing, while, the diameter change has little effect on the temperature of front surface. The air exit temperature increases apparently with decrease of air flow rate and rise of inlet air temperature, and increases with increase of incident radiation intensity. The energy absorbing efficiency is decreasing with decrease of air flow rate and rise of inlet air temperature, and decreases with increase of incident radiation intensity. The presented secondary heating type of receiver can improve the energy absorbing efficiency, although the feasibility and economy of this consideration need further verification in future.
关键词： volumetric solar receiver,porous foam ceramics,temperature distribution,radiation absorption efficiency,secondary heating
更新于2025-09-23 15:21:21
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Weak coherent pulses for single-photon quantum memories
摘要： Attenuated laser pulses are often employed in place for single photons in order to test the efficiency of the elements of a quantum network. In this work we analyse theoretically the dynamics of storage of an attenuated light pulse (where the pulse intensity is at the single photon level) propagating along a transmission line and impinging on the mirror of a high finesse cavity. Storage is realised by the controlled transfer of the photonic excitations into a metastable state of an atom confined inside the cavity and occurs via a Raman transition with a suitably tailored laser pulse, which drives the atom and minimizes reflection at the cavity mirror. We determine the storage efficiency of the weak coherent pulse which is reached by protocols optimized for single-photon storage. We determine the figures of merit and we identify the conditions on an arbitrary pulse for which the storage dynamics approaches the one of a single photon. Our formalism can be extended to arbitrary types of input pulses and to quantum memories composed by spin ensembles, and serves as a basis for identifying the optimal protocols for storage and readout.
关键词： storage efficiency,single-photon,weak coherent pulse,quantum network,quantum memory
更新于2025-09-23 15:21:21
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High efficiency???low efficiency roll-off and long lifetime fluorescent white organic light-emitting diodes based on strategic management of triplet excitons via triplet-triplet annihilation up-conversion and phosphor sensitization
摘要： The simultaneous realization of high efficiency, low efficiency roll-off, long lifetime and stable electroluminescence (EL) spectra in fluorescent white organic light-emitting diodes (WOLEDs) is still a huge challenge. Here, we used a triplet-triplet annihilation up-conversion (TTA-UC) material as blue emission layer and phosphor sensitized fluorescent emitter as red emission layer and introduced a bipolar interlayer between them to fabricate high efficiency, low efficiency roll-off and long lifetime fluorescent WOLEDs. It is clearly seen that the bipolar interlayer not only efficiently distributed the singlet and triplet excitons, but also significantly stabilized the EL spectra. Thus, the resulting two-color fluorescent WOLEDs exhibited the maximum current efficiency (CE), power efficiency (PE) and external quantum efficiency (EQE) of 26.9 cd A-1, 22.3 lm W-1 and 12.8%, and remained 25.9 cd A-1, 16.9 lm W-1 and 12.1% at the luminance of 1000 cd m-2 and 23.1 cd A-1, 10.6 lm W-1 and 10.7% at the luminance of 10000 cd m-2, respectively, and the operational lifetime LT50 (50% decay, initial luminance of 1000 cd m-2) was also up to 984 h. It can be seen that these devices also showed stable EL spectra with Commission Internationale de I’Eclairage (CIE) of (0.51, 0.41) from 1000 cd m-2 to 5000 cd m-2 luminance. Furthermore, the fabricated three-color fluorescent WOLEDs by further introducing a green fluorescent emitter, also showed high efficiencies of 15.5 cd A-1, 13.0 lm W-1 and 8.1% and stable EL spectra with CIE of (0.43, 0.36) form 1000 cd m-2 to 5000 cd m-2 luminance. More importantly, their CE and EQE exhibited an increasing tendency with the luminance, a fully negligible efficiency roll-off. This design strategy provides a potential route towards high performance fluorescent WOLEDs.
关键词： fluorescent WOLEDs,bipolar interlayer,high efficiency,triplet-triplet annihilation up-conversion,phosphor sensitization,long lifetime,low efficiency roll-off
更新于2025-09-23 15:21:01
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Subwavelength-scale nanorods implemented hexagonal pyramids structure as efficient light-extraction in Light-emitting diodes
摘要： Subwavelength-scale nanorods were implemented on the hexagonal pyramid of photochemically etched light-emitting diodes (LEDs) to improve light extraction efficiency (LEE). Sequential processes of Ag deposition and inductively coupled plasma etching successfully produce nanorods on both locally unetched flat surface and sidewall of hexagonal pyramids. The subwavelength-scale structures on flat surface offer gradually changed refractive index, and the structures on side wall of hexagonal pyramid reduce backward reflection, thereby enhancing further enhancement of the light extraction efficiency. Consequently, the nanorods implemented LED shows a remarkable enhancement in the light output power by 14% compared with that of the photochemically etched LEDs which is known to exhibit the highest light output power. Theoretical calculations using a rigorous coupled wave analysis method reveal that the subwavelength-scale nanorods are very effective in the elimination of TIR as well as backward reflections, thereby further enhancing LEE of the LEDs.
关键词： subwavelength-scale nanorods,light-emitting diodes,light extraction efficiency,hexagonal pyramids,photochemical etching
更新于2025-09-23 15:21:01
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Novel strategy to improve the efficiency roll-off at high luminance and operational lifetime of hybrid white OLEDs via employing an assistant layer with triplet-triplet annihilation up-conversion characteristics
摘要： The efficiency roll-off at high luminance and operational lifetime remain a major challenge before the wide applications of white organic light-emitting diodes (WOLEDs) technology. Here we present a novel strategy to improve the efficiency roll-off at high luminance and operational lifetime by employing an assistant layer with triplet-triplet annihilation (TTA) up-conversion characteristics in emitters. It can be seen that at high luminance, the partial triplet energies in emitters will transfer to the TTA assistant layer and finally lead to the TTA emission, which reduces the exciton quenching at high luminance. Therefore, not only the efficiency roll-off, but also the operational lifetime are greatly improved. The resulting hybrid WOLEDs exhibited the maximum forward-viewing external quantum efficiency and power efficiency of 23.6% and 68.8 lm W?1, and they only dropped to 18.3% and 38.1 lm W?1 at 1000 cd m?2 and 17.1% and 25.9 lm W?1 at 5000 cd m?2, which are significantly higher than 10.5% and 17.9 lm W?1 at 5000 cd m?2 of WOLEDs without TTA assistant layer. Furthermore, the operational half-lifetime of the resulting hybrid WOLEDs also reached 600 hours at the luminance of 1000 cd m?2, which is nearly two-fold longer than that of the reference WOLEDs.
关键词： exciton diffusion,triplet-triplet annihilation up-conversion,Efficiency roll-off,white organic light-emitting diodes,lifetime
更新于2025-09-23 15:21:01
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Enhancement in the performance of nanostructured CuOa??ZnO solar cells by band alignment
摘要： In this study, we investigated the effect of cobalt doping on band alignment and the performance of nanostructured ZnO/CuO heterojunction solar cells. ZnO nanorods and CuO nanostructures were fabricated by a low-temperature and cost-effective chemical bath deposition technique. The band offsets between Zn1?xCoxO (x = 0, 0.05, 0.10, 0.15, and 0.20) and CuO nanostructures were estimated using X-ray photoelectron spectroscopy and it was observed that the reduction of the conduction band offset with CuO. This also results in an enhancement in the open-circuit voltage. It was demonstrated that an optimal amount of cobalt doping could effectively passivate the ZnO related defects, resulting in a suitable conduction band offset, suppressing interface recombination, and enhancing conductivity and mobility. The capacitance–voltage analysis demonstrated the effectiveness of cobalt doping on enhancing the depletion width and built-in potential. Through impedance spectroscopy analysis, it was shown that recombination resistance increased up to 10% cobalt doping, thus decreased charge recombination at the interface. Further, it was demonstrated that the insertion of a thin layer of molybdenum oxide (MoO3) between the active layer (CuO) and the gold electrode hinders the formation of a Schottky junction and improved charge extraction at the interface. The ZnO/CuO solar cells with 10% cobalt doped ZnO and 20 nm thick MoO3 buffer layer achieved the best power conversion efficiency of 2.11%. Our results demonstrate the crucial role of the band alignment on the performance of the ZnO/CuO heterojunction solar cells and could pave the way for further progress on improving conversion efficiency in oxide-based heterojunction solar cells.
关键词： nanostructured,solar cells,X-ray photoelectron spectroscopy,power conversion efficiency,molybdenum oxide,chemical bath deposition,band alignment,CuO–ZnO,cobalt doping
更新于2025-09-23 15:21:01