- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Superradiance as a Way to the Steady-State Multimode and Ultrashort Pulsed Lasing in CW Quantum-Dot Heterolasers
摘要： On the basis of the Maxwell-Bloch equations, we demonstrate theoretically and numerically that the pulsed superradiant lasing is possible in the quantum-dot heterostructures under continuous-wave (CW) optical pumping if the quantum-dot coherence lifetime exceeds the photon lifetime in a laser cavity [1, 2]. We analyze/compare in detail and select the most promising multilayered well-dot and sub-monolayer quantum-dot heterostructures which could be used as the active media, and design for them the proper low-Q combined Fabry-Perot cavities with distributed feedback which will select the superradiant modes. We investigate various operational regimes of the superradiant lasing and the intriguing quantum-coherent features of both cooperative and individual dynamics of quantum dots under the action of a self-consistent intracavity field preserving the long-term and wide-spectral coherence. Among the remarkably diverse operational regimes of the laser, we find the quasi-stationary, self-modulated, regular or irregular pulsed, self-locked, and stochastic regimes. In particular, we show that one or several superadiant modes may emit the quasiperiodic sequences of ultrashort subpicosecond pulses with comparable periods of the order of picoseconds and at the same time give rise to many steady-state modes with quasi-equidistant spectrum (see a fig. 1). The letter used to be self-locked due to the superradiant coherent dynamics of quantum dots, so that an additional sequence of ultrashort subpicosecond pulses with a round-trip period are emitted in the absence of any active or passive mode-locking elements. We indicate the ways how (i) to overcome an additional relaxation of the quantum-dot coherence in the presence of incoherent pumping and suppression of the superradiant gain within an inhomogeneously broadened spectral line of quantum dots continuously, i.e., during the entire time of laser operation, and (ii) to ensure a fully cycling pump-emission scheme of the quantum dots’ dynamics including a fast depletion of the lower-energy states under a CW pumping of the upper-energy states and to minimize extra heating which accompanies this cycling process and increases the relaxation of coherence. The suggested pulsed multimode superradiant heterolaser will offer a number of applications in the information optics, data processing, fiber network systems, wideband dynamic spectroscopy and diagnostics of various materials since it will be the first compact source of coherent radiation with a wide variety of controllable quantum-correlation and spectral-temporal properties. Also, such a heterolaser is a unique object for the studies of complex coherent processes in the semiconductor heterostructures.
关键词： Continuous-Wave Optical Pumping,Ultrashort Pulsed Lasing,Quantum-Dot Heterolasers,Maxwell-Bloch Equations,Superradiance
更新于2025-09-12 10:27:22
-
Photo-Patternable Quantum Dots/Siloxane Composite with Long-Term Stability for Quantum Dot Color-Filters
摘要： Incorporation of quantum dots (QDs) into color-filters (CFs) are desired for less energy loss and wider viewing angle compared to conventional display. However, aggregation and vulnerability to heat, moisture, and chemicals in photo-patternable matrix are critical issues of the QD-CFs with high QDs concentration. Herein, we fabricated red (10 wt%) and green (20 wt%) QD-CFs using photolithography of QD/siloxane ink containing secondary thiol monomer. Ligand exchanged QDs were chemically incorporated in methacrylate oligo-siloxane resin. QD/siloxane composite showed superior stability under harsh heat and moisture (85 ℃/5% RH and 85 ℃/85% RH) conditions and chemicals (EtOH, HCl and NaOH) compared to conventional QD/PR (commercial negative photoresist). 10 μm-thick QD-CFs effectively converted blue light emitted from LED chip into red and green light, and the obtained white PL through QD-CF showed wide color gamut which was 108% relative to NTSC. From these advantages, QD/siloxane composite will be beneficial as color-conversion photoresist to be used as color-filters in LCDs, μLEDs, and OLEDs.
关键词： Sol-gel condensation,Siloxane hybrids,Photo-patternability,Quantum dot color-filter,Thermal and chemical stability
更新于2025-09-12 10:27:22
-
Silicene Quantum Dots Confined in Few-Layer Siloxene Nanosheets for Blue Light-Emitting Diodes
摘要： Two-dimensional silicon-based materials have unique physical and chemical properties due to high surface area and quantum confinement effects. Herein, a topochemical reaction method is used for preparing silicene quantum dots confined in few layer siloxene nanosheets with FeCl3?6H2O as oxidant, which shows thickness less than 2 nm. The experimentally prepared siloxene nanosheets are dispersible, with silicene quantum dots having average diameter less than 5 nm. The silicene quantum dots are self-organized through the oxidation of FeCl3, showing unique optical properties of blue emission. The UV-visible absorption and PL emission spectra indicate the quasi-direct band gap transition to the emission. Besides, the few-layer siloxene nanosheets with silicene quantum dots have a radiative lifetime of 1.098 ns at an emission wavelength of 435 nm, which derives from the quasi-direct band transition of silicene quantum dots. Such two-dimensional nanosheets of silicon possess potential applications for the emitting layer materials of blue light-emitting diodes (LED).
关键词： topochemical reaction,silicene quantum dot,photoluminescence,siloxene,quasi-direct band gap
更新于2025-09-12 10:27:22
-
Efficiency Limit of Colloidal Quantum Dot Solar Cells: Effect of Optical Interference on Active Layer Absorption
摘要： Recently, colloidal quantum dot (CQD) solar cells have drawn intense attention because of their accessibility in low-energy solar photons with a facile tunability in electrical properties and their promising feature to go beyond the classic Shockley?Queisser limit of solar cells. Currently, state-of-the-art performance lead sulfide CQD thin-film-based solar cells have a PCE of approximately 12% with large room for improvement. To overcome current limitations on efficiency enhancement in CQD thin-film solar cells, the active layer thickness must increase first by improving carrier transport and formation of band bending to improve collection of carriers. We must note, however, in this heterojunction architecture, estimated optimal active layer thickness has to be revisited considering the interference effect. Specifically, the large refractive index difference between the PbS CQD layer and the ZnO layers account for a significant Fresnel reflection and optical interference in PbS CQD solar cells. This interference effect on high-performing PbS CQD solar cells may not only reduce the effective light absorption but also lead to underestimating the optimal active layer thickness.
关键词： colloidal quantum dot solar cells,optical interference,efficiency limit,active layer absorption
更新于2025-09-12 10:27:22
-
Bandgap Tunable Ternary Cd <sub/><i>x</i> </sub> Sb <sub/> 2– <i>y</i> </sub> S <sub/>3?δ</sub> Nanocrystals for Solar Cell Applications
摘要： We report the synthesis and photovoltaic performance of a new nonstoichiometric ternary metal sulfide alloyed semiconductor?CdxSb2?yS3?δ nanocrystals prepared by the two-stage sequential ionic layer adsorption reaction technique. The synthesized CdxSb2?yS3?δ nanocrystals retain the orthorhombic structure of the host Sb2S3 with Cd substituting a fraction (x = 0?0.15) of the cationic element Sb. The CdxSb2?yS3?δ lattice expands relative to the host, Sb2S3, with its lattice constant a increasing linearly with Cd content x. Optical and external quantum efficiency (EQE) spectra revealed that the bandgap Eg of CdxSb2?yS3?δ decreased from 1.99 to 1.69 eV (i.e., 625?737 nm) as x increased from 0 to 0.15. Liquid-junction CdxSb2?yS3?δ quantum dot-sensitized solar cells were fabricated using the polyiodide electrolyte. The best cell yielded a power conversion efficiency (PCE) of 3.72% with the photovoltaic parameters of Jsc = 15.97 mA/cm2, Voc = 0.50 V, and FF = 46.6% under 1 sun. The PCE further increased to 4.86%, a respectable value for a new solar material, under a reduced light intensity of 10% sun. The PCE (4.86%) and Jsc (15.97 mA/cm2) are significantly larger than that (PCE = 1.8%, Jsc = 8.55 mA/cm2) of the Sb2S3 host. Electrochemical impedance spectroscopy showed that the ZnSe passivation coating increased the electron lifetime by three times. The EQE spectrum of CdxSb2?yS3?δ has a maximal EQE of 82% at λ = 350 nm and covers the spectral range of 300?750 nm, which is significantly broader than that (300?625 nm) of the Sb2S3 host. The EQE-integrated current density yields a Jph of 11.76 mA/cm2. The tunable bandgap and a respectable PCE near 5% suggest that CdxSb2?yS3?δ could be a potential candidate for a solar material.
关键词： ternary metal sulfide,CdxSb2?yS3?δ nanocrystals,photovoltaic performance,quantum dot-sensitized solar cells,bandgap tunable
更新于2025-09-12 10:27:22
-
Improved light-harvesting and suppressed charge recombination by introduction of a nanograss-like SnO <sub/>2</sub> interlayer for efficient CdS quantum dot sensitized solar cells
摘要： Quantum dot sensitized solar cell (QDSSC) performance is primarily limited by the recombination of charges at the interfaces of TiO2/quantum dot (QD) sensitizer/electrolyte. Hence, blocking or suppressing the charge recombination is an essential requirement to elevate the QDSSC performance to the next level. To retard the charge recombination, herein, we propose the introduction of a SnO2 nanograss (NG) interlayer on the surface of TiO2 using the facile chemical bath deposition method. The SnO2 NG interlayer not only inhibits the interfacial recombination processes in QDSSCs but also enhances the light-harvesting capability in generating more excitons. Hence, the TiO2/SnO2 NG/CdS QDSSCs can achieve the power conversion efficiency of 3.15%, which is superior to that of a TiO2/CdS device (2.16%). Electrochemical impedance spectroscopy, open-circuit voltage decay and dark current analyses confirm that the photoanode/electrolyte interface is suppressed and the life time is improved by introducing the SnO2 NG interlayer between the TiO2 and CdS QD sensitizer.
关键词： Charge recombination,SnO2 nanograss,Light-harvesting,Chemical bath deposition,Quantum dot sensitized solar cells
更新于2025-09-12 10:27:22
-
Highly Efficient and Bright Inverted Top‐Emitting InP Quantum Dot Light‐Emitting Diodes Introducing a Hole‐Suppressing Interlayer
摘要： InP quantum dots (QDs) based light-emitting diodes (QLEDs) are considered as one of the most promising candidates as a substitute for the environmentally toxic Cd-based QLEDs for future displays. However, the device architecture of InP QLEDs is almost the same as the Cd-based QLEDs even though the properties of Cd-based and InP-based QDs are quite different in their energy levels and shapes. Thus, it is highly required to develop a proper device structure for InP-based QLEDs to improve the efficiency and stability. In this work, efficient, bright, and stable InP/ZnSeS QLEDs based on an inverted top emission QLED (ITQLED) structure by newly introducing a “hole-suppressing interlayer” are demonstrated. The green-emitting ITQLEDs with the hole-suppressing interlayer exhibit a maximum current efficiency of 15.1–21.6 cd A?1 and the maximum luminance of 17 400–38 800 cd m?2, which outperform the recently reported InP-based QLEDs. The operational lifetime is also increased when the hole-suppressing interlayer is adopted. These superb QLED performances originate not only from the enhanced light-outcoupling by the top emission structure but also from the improved electron–hole balance by introducing a hole-suppressing interlayer which can control the hole injection into QDs.
关键词： indium phosphide,top emitting structure,efficiency,quantum dot–based light emitting diodes (QLEDs),hole suppressing interlayer
更新于2025-09-12 10:27:22
-
Phonon-Induced Enhancement of Photon Entanglement in Quantum Dot-Cavity Systems
摘要： We report on simulations of the degree of polarization entanglement of photon pairs simultaneously emitted from a quantum dot-cavity system that demand revisiting the role of phonons. Since coherence is a fundamental precondition for entanglement and phonons are known to be a major source of decoherence, it seems unavoidable that phonons can only degrade entanglement. In contrast, we demonstrate that phonons can cause a degree of entanglement that even surpasses the corresponding value for the phonon-free case. In particular, we consider the situation of comparatively small biexciton binding energies and either finite exciton or cavity mode splitting. In both cases, combinations of the splitting and the dot-cavity coupling strength are found where the entanglement exhibits a nonmonotonic temperature dependence which enables entanglement above the phonon-free level in a finite parameter range. This unusual behavior can be explained by phonon-induced renormalizations of the dot-cavity coupling g in combination with a nonmonotonic dependence of the entanglement on g that is present already without phonons.
关键词： decoherence,phonon-induced enhancement,photon entanglement,quantum dot-cavity systems,polarization entanglement
更新于2025-09-12 10:27:22
-
Effect of Temperature on the Single-Particle Ground-State and Self Energy of a Polar Quantum Dot with Gaussian Confinement
摘要： The temperature dependence of the properties of a polaron in a Gaussian quantum dot has been investigated by using Lee-Low-Pines-Hybrechts variational technique and quantum statistical mechanics. It is shown that the ground-state energy increases with increasing temperature and the corresponding polaronic correction decreases. It is thus shown that for entire range of the coupling constant, polaronic effects decrease with increasing temperature.
关键词： Temperature effect,Polaron self-energy,Quantum dot,Gaussian confinement
更新于2025-09-12 10:27:22
-
Enhanced CH4 selectivity in CO2 photocatalytic reduction over carbon quantum dots decorated and oxygen doping g-C3N4
摘要： Graphitic carbon nitride (g-C3N4, CN) exhibits inefficient charge separation, deficient CO2 adsorption and activation sites, and sluggish surface reaction kinetics, which have been recognized as the main barriers to its application in CO2 photocatalytic reduction. In this work, carbon quantum dot (CQD) decoration and oxygen atom doping were applied to CN by a facile one-step hydrothermal method. The incorporated CQDs not only facilitate charge transfer and separation, but also provide alternative CO2 adsorption and activation sites. Further, the oxygen-atom-doped CN (OCN), in which oxygen doping is accompanied by the formation of nitrogen defects, proves to be a sustainable H+ provider by facilitating the water dissociation and oxidation half-reactions. Because of the synergistic effect of the hybridized binary CQDs/OCN addressing the three challenging issues of the CN based materials, the performance of CO2 photocatalytic conversion to CH4 over CQDs/OCN-x (x represents the volume ratio of laboratory-used H2O2 (30 wt.%) in the mixed solution) is dramatically improved by 11 times at least. The hybrid photocatalyst design and mechanism proposed in this work could inspire more rational design and fabrication of effective photocatalysts for CO2 photocatalytic conversion with a high CH4 selectivity.
关键词： carbon quantum dot,photocatalytic,graphitic carbon nitride (g-C3N4),oxygen doping,CO2 reduction
更新于2025-09-12 10:27:22