- 标题
- 摘要
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- 实验方案
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Improved photovoltaic performance of perovskite solar cells by utilizing down-conversion NaYF <sub/>4</sub> :Eu <sup>3+</sup> nanophosphors
摘要： Perovskite solar cells assembled with titanium dioxide electron transport layer exhibited brilliant photovoltaic properties due to titanium dioxide having a high electron mobility, appropriate energy level alignment and easy fabrication procedure. However, inherent instability exists in titanium dioxide-based perovskite solar cells because of the ultraviolet photocatalytic activity of titanium dioxide. This results in recombination at the interface of titanium dioxide/perovskite. In this report, the down-conversion nanocrystals film made of europium-doped sodium yttrium fluoride was deposited on the non-conducting side of the conducting glass. The down-conversion nanocrystal layer could absorb high energy ultraviolet photons and converted them to visible light. The layer not only extended the spectral response range for perovskite solar cells but also alleviated the photocatalytic activity of titanium dioxide. The perovskite solar cells with the down-conversion nanocrystals film generated average power conversion efficiency yield of 19.99%, which is much better than that of the device without the down-conversion nanocrystals film (16.99%). The best power conversion efficiency for the device with the down-conversion nanocrystals film was 20.17%. In addition, perovskite solar cells with the down-conversion nanocrystals film showed a small hysteresis.
关键词： titanium dioxide,down-conversion,NaYF4:Eu3+ nanophosphors,photovoltaic performance,perovskite solar cells
更新于2025-11-14 17:04:02
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Photoluminescence properties of Er3+/Yb3+ doped ZrO2 coatings formed by plasma electrolytic oxidation
摘要： In the present work, down- and up-conversion photoluminescence properties of Er3+/Yb3+ doped ZrO2 coatings formed by plasma electrolytic oxidation of zirconium in electrolyte containing Er2O3 and Yb2O3 particles were investigated. Down-conversion PL analysis shows that emission spectra of ZrO2:Er3+/Yb3+ coatings excited with 280 nm radiation are composed of broad PL band related to ZrO2 host and bands assigned to f-f transitions of Er3+. The main PL emission bands of Er3+ at around 548 nm and 560 nm are related to 4S3/2→4I15/2 transition. PL excitation spectra monitored at 548 nm feature broad band in the region from 250 nm to 350 nm which is associated with the electron transfer transition from 2p orbital of O2? to 4f orbital of Er3+ and transitions of ZrO2. On the other hand, bands in PL excitation spectra ranging from 350 nm to 535 nm are related to 4f transitions of the Er3+ from the ground state 4I15/2 to higher energy levels. Down-conversion PL intensity decreases with increasing concentration of Yb3+ in coating due to energy transfer from Er3+ to Yb3+. ZrO2:Er3+/Yb3+ coatings show intense green (4S3/2→4I15/2) and red (4F9/2→4I15/2) up-conversion PL emission under the excitation with a 980 nm diode laser. With increasing Yb3+ concentration red up-conversion PL intensity increases more rapidly with respect to green emission, because red up-conversion PL intensity strongly depends on Yb3+ concentration, i.e. 4F9/2 state of Er3+ is directly excited by energy transfer from excited Yb3+.
关键词： up-conversion,Photoluminescence,Er3+/Yb3+,Down-conversion,Plasma electrolytic oxidation
更新于2025-09-23 15:23:52
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Phase Conjugation and Mode Conversion in Stimulated Parametric Down-Conversion with Orbital Angular Momentum: a Geometrical Interpretation
摘要： We report on an experiment that investigates the spatial mode conversion in the process of parametric down-conversion seeded by a light beam in a superposition of orbital angular momentum modes. This process is interpreted in terms of a geometric representation of first-order spatial modes in a Poincaré sphere, providing an intuitive image of the phase conjugation and the topological charge conservation. We also make a comparison with the analogous phenomenon for optical parametric oscillators.
关键词： Orbital angular momentum,Parametric down-conversion,Optics,Phase conjugation
更新于2025-09-23 15:23:52
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Leakage Mitigation in Heterodyne FMCW Radar for Small Drone Detection With Stationary Point Concentration Technique
摘要： To prevent potential hazards posed by fast-evolving drones, it is of importance to develop a radar system for drone detection. Frequency modulated continuous wave (FMCW) radars are widely used for that purpose. Heterodyne architectures are preferred for them to mitigate dc offset errors. Having said that, FMCW radars suffer from permanent leakage from the transmitter into the receiver. The leakage phase noise raises the total noise floor and limits the radar sensitivity. Here, we propose a stationary point concentration (SPC) technique in order to overcome the challenges. The SPC technique concentrates the leakage phase noise on a stationary point to alleviate the impact of the noise. The technique can be realized using digital signal processing without additional hardware. The results show that the proposed technique significantly lowers the noise floor.
关键词： heterodyne,down-conversion,leakage,digital signal processing (DSP),frequency modulated continuous wave (FMCW) radar,stationary point concentration (SPC) technique,stationary point,phase noise,noise floor
更新于2025-09-23 15:22:29
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Generation of optical signal and terahertz idler photons by spontaneous parametric down-conversion
摘要： Frequency-angular characteristics of signal and idler photons generated under spontaneous parametric down-conversion are studied in a strongly frequency nondegenerate regime, without paraxial approximation, accounting for possible inherent absorption of idler waves in a nonlinear crystal, classical thermal field fluctuations, and the multimode character of parametric interaction induced by transverse spatial limitation of the pump beam. Spatial limitation is shown to lead to a huge increase in angular divergence of the idler photons generated at terahertz frequencies. General expressions are obtained for the frequency-angular sensitivity function of the nonlinear-optical terahertz wave detector and for power densities of the signal and idler photon fluxes. The absorption-induced difference in the parametric conversion coefficients for the noise and externally incident radiation of the idler frequency is shown to be described by approximately the same loss factor for all active spatial idler modes. Two different parametric contributions of the internal thermal noise to the number of output idler photons were revealed with different dependence on the idler-wave absorption. Expressions for the loss factors, which describe absorption-induced effects in signal and idler channels, are obtained and shown to be turning into one another by changing the sign of the absorption coefficient. Relative contribution of thermal and quantum field fluctuations into the intrinsic radiation of a nonlinear crystal at signal and idler frequencies is analyzed accounting for the crystal absorption properties.
关键词： nonlinear optics,thermal fluctuations,terahertz,quantum fluctuations,absorption,spontaneous parametric down-conversion
更新于2025-09-23 15:22:29
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[IEEE 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Chengdu, China (2018.5.7-2018.5.11)] 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Design of a Novel Broadband Down Conversion Module
摘要： This paper introduces the design of a novel broadband down conversion module. Firstly the design method of interference signal suppression is presented. Through the application of various of filters, all kinds of interference signals are suppressed to some extent, which satisfies the requirements of the whole system requirement against interference.
关键词： down conversion,hairpin filter,anti-jamming
更新于2025-09-23 15:22:29
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High concentration Eu3+-doped NaYb(MoO4)2 multifunctional material: Thermometer and plant growth lamp matching phytochrome PR
摘要： Phytochromes PR and PFR are distributed in various organs of plant, phytochrome PR absorbs red light and phytochrome PFR absorbs far-red light, respectively, so the flower induction, etc. can be controlled by changing the ratio of red light to far-red light. The emission of Eu3+ (transition from 5D0/7F2) is located at the red range and matches with the absorption band of PR. Herein, we synthesized successfully NaYb(MoO4)2: Eu3+ phosphors with the high doping concentration (50%) by hydrothermal method with further calcinations. The LED device was also fabricated by the blue InGaN chip combined with the red phosphors NaYb(MoO4)2: 50%Eu3+ based on the excellent luminescent intensity. Moreover, the effect of temperature on the excitation intensity ratio of MoO4 2- to Eu3+ has also been studied, which provided the possibility of simultaneous luminescence and temperature measurement. This work is the first time to use Eu3+ as a red source matching PR, and the red phosphors have potential value to control plant growth.
关键词： Down-conversion luminescence,Temperature sensing,LEDs,Plant cultivation,Red phosphors
更新于2025-09-23 15:22:29
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Terahertz generation in quantum-cascade lasers through down-conversion optical nonlinearity: Design and modeling
摘要： In this paper, we propose an electrically driven optically excited laser structure for terahertz (THz) generation in quantum cascade lasers (QCLs) through frequency down-conversion optical nonlinearity. In our distinct design, both the pump and THz radiations are generated simultaneously by optical and electronic intersubband transitions (ISTs) between the quantized states within the conduction band of the same active region of a QCL. The modeling of laser bandstructure is achieved using a self-consistent solution of Schrodinger-Poisson equations, and the detailed analysis of electronic transport of the proposed structure is performed using the density matrix approach and energy-density balance equation that self-consistently consider the optical, electrical and thermal interactions in the structure. Additionally, the waveguide loss for the THz optical mode is considered using the bulk Drude model. Using a stationary solution of the density matrix equations, an expression for the THz intensity gain is derived as a function of pump field intensity, carrier distributions and quantum coherence contributions. Using the presented model, we analyze the steady-state and transient characteristics of the device for two different heatsink temperatures, 220 and 300 K. Simulation results show that the proposed structure has a potential to generate room-temperature THz radiation in QCLs.
关键词： Quantum-cascade laser (QCL),terahertz (THz) generation,down-conversion optical nonlinearity,density-matrix formalism
更新于2025-09-23 15:21:01
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[IEEE 2019 7th International Renewable and Sustainable Energy Conference (IRSEC) - Agadir, Morocco (2019.11.27-2019.11.30)] 2019 7th International Renewable and Sustainable Energy Conference (IRSEC) - Elaboration and Characterization of (Ce,Sm) Doped Lanthanum Oxychloride for Photovoltaic Solar Cell
摘要： The spectral incoherence due to the emission of sunlight and the absorption of silicon solar cells cause large solar energy losses, leading to a low photovoltaic efficiency. So that low energy photons cannot be used efficiently, while the majority of high energy photons are dissipate. Doped rare earth ions (RE) are expected to solve this problem, thanks to their spectral modification characteristics and luminescence properties. In this work we present the synthesis of LaOCl co-doped by trivalent rare earth with the couple of Ce3+/Sm3+ employed in photovoltaic cell down conversion. LaOCl: Ce3+/Sm3+ phosphors were prepared by the solid-state method, and their structures properties were investigated by using X-ray diffraction, Infrared Spectroscopy and MEB analysis. The study shows that tetragonal LaOCl: Ce3+/Sm3+ can be synthesized by the solid-state reaction at 700 °C for 4 h.
关键词： Down conversion,Lanthanum oxychloride,Solid-state,Photovoltaic,Rare Earth
更新于2025-09-23 15:21:01
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Photon-number parity of heralded single photons from a Bragg-reflection waveguide reconstructed loss-tolerantly via moment generating function
摘要： Due to their strict photon-number correlation, the twin beams produced in parametric down-conversion (PDC) work well for heralded state generation. Often, however, this state manipulation is distorted by the optical losses in the herald and by the higher photon-number contributions inevitable in the PDC process. In order to find feasible figures of merit for characterizing the heralded states, we investigate their normalized factorial moments of the photon number that can be accessed regardless of the optical losses in the detection. We then perform a measurement of the joint photon statistics of twin beams from a semiconductor Bragg-reflection waveguide with transition-edge sensors acting as photon-number-resolving detectors. We extract the photon-number parity of heralded single photons in a loss-tolerant fashion by utilizing the moment generating function. The photon-number parity is highly practicable in quantum state characterization, since it takes into account the complete photon-number content of the target state.
关键词： Bragg-reflection waveguide,photon-number parity,transition-edge sensor,moment generating function,factorial moment of photon number,parametric down-conversion
更新于2025-09-23 15:19:57