Full-color displays based on micro light-emitting diodes(μLEDs) can be fabricated on monolithic epitaxial wafers. Nanoring(NR) structures were fabricated on a green LED epitaxial wafer; the color of NR-μLEDs was tun...Full-color displays based on micro light-emitting diodes(μLEDs) can be fabricated on monolithic epitaxial wafers. Nanoring(NR) structures were fabricated on a green LED epitaxial wafer; the color of NR-μLEDs was tuned from green to blue through strain relaxation. An Al_2O_3 layer was deposited on the sidewall of NR-μLEDs,which improved the photoluminescence intensity by 143.7%. Coupling with the exposed multiple quantum wells through nonradiative resonant energy transfer, red quantum dots were printed to NR-μLEDs for a full-color display. To further improve the color purity of the red light, a distributed Bragg reflector is developed to reuse the excitation light.展开更多
Red-green-blue(RGB)full-color micro light-emitting diodes(μ-LEDs)fabricated from semipolar(20-21)wafers,with a quantum-dot photoresist color-conversion layer,were demonstrated.The semipolar(20-21)In Ga N/Ga Nμ-LEDs ...Red-green-blue(RGB)full-color micro light-emitting diodes(μ-LEDs)fabricated from semipolar(20-21)wafers,with a quantum-dot photoresist color-conversion layer,were demonstrated.The semipolar(20-21)In Ga N/Ga Nμ-LEDs were fabricated on large(4 in.)patterned sapphire substrates by orientation-controlled epitaxy.The semipolarμ-LEDs showed a 3.2 nm peak wavelength shift and a 14.7%efficiency droop under 200 A∕cm2injected current density,indicating significant amelioration of the quantum-confined Stark effect.Because of the semipolarμ-LEDs’emission-wavelength stability,the RGB pixel showed little color shift with current density and achieved a wide color gamut(114.4%NTSC space and 85.4%Rec.2020).展开更多
Augmented reality(AR)and virtual reality(VR)are two novel display technologies that are under updates.The essential feature of AR/VR is the full-color display that requires high pixel densities.To generate three-color...Augmented reality(AR)and virtual reality(VR)are two novel display technologies that are under updates.The essential feature of AR/VR is the full-color display that requires high pixel densities.To generate three-color pixels,the fluorescent color conversion layer inevitably includes green and red pixels.To fabricate such sort of display kits,inkjet printing is a promising way to position the color conversion layers.In this review article,the progress of AR/VR technologies is first reviewed,and in succession,the state of the art of inkjet printing,as well as two key issues-the optimization of ink and the reduction of coffee-ring effects,are introduced.Finally,some potential problems associated with the color converting layer are highlighted.展开更多
Silicon(Si)has become the most promising material for monolithic integrated photonic circuits with a wide range of scientific and industrial applications.A variety of Si photonic components,such as optical waveguides,...Silicon(Si)has become the most promising material for monolithic integrated photonic circuits with a wide range of scientific and industrial applications.A variety of Si photonic components,such as optical waveguides,optical modulators and photodetectors,have been successfully demonstrated,however,silicon lasers have not yet been achieved due to the low efficiency of Si emission.In 2000,Pavesi et al.[1]reported the first observation of展开更多
Deeply subwavelength lasers(or nanolasers)are highly demanded for compact on-chip bioimaging and sensing at the nanoscale.One of the main obstacles for the development of single-particle nanolasers with all three dime...Deeply subwavelength lasers(or nanolasers)are highly demanded for compact on-chip bioimaging and sensing at the nanoscale.One of the main obstacles for the development of single-particle nanolasers with all three dimensions shorter than the emitting wavelength in the visible range is the high lasing thresholds and the resulting overheating.Here we ex-ploit exciton-polariton condensation and mirror-image Mie modes in a cuboid CsPbBr3 nanoparticle to achieve coherent emission at the visible wavelength of around 0.53μm from its ultra-small(≈0.007μm3 or≈λ3/20)semiconductor nanocav-ity.The polaritonic nature of the emission from the nanocavity localized in all three dimensions is proven by direct com-parison with corresponding one-dimensional and two-dimensional waveguiding systems with similar material parameters.Such a deeply subwavelength nanolaser is enabled not only by the high values for exciton binding energy(≈35 meV),re-fractive index(>2.5 at low temperature),and luminescence quantum yield of CsPbBr3,but also by the optimization of po-laritons condensation on the Mie resonances with quality factors improved by the metallic substrate.Moreover,the key parameters for optimal lasing conditions are intermode free spectral range and phonons spectrum in CsPbBr3,which govern polaritons condensation path.Such chemically synthesized colloidal CsPbBr3 nanolasers can be potentially de-posited on arbitrary surfaces,which makes them a versatile tool for integration with various on-chip systems.展开更多
Gait is a biological typical that defines the method by that people walk.Walking is the most significant performance which keeps our day-to-day life and physical condition.Surface electromyography(sEMG)is a weak bioel...Gait is a biological typical that defines the method by that people walk.Walking is the most significant performance which keeps our day-to-day life and physical condition.Surface electromyography(sEMG)is a weak bioelectric signal that portrays the functional state between the human muscles and nervous system to any extent.Gait classifiers dependent upon sEMG signals are extremely utilized in analysing muscle diseases and as a guide path for recovery treatment.Several approaches are established in the works for gait recognition utilizing conventional and deep learning(DL)approaches.This study designs an Enhanced Artificial Algae Algorithm with Hybrid Deep Learning based Human Gait Classification(EAAA-HDLGR)technique on sEMG signals.The EAAA-HDLGR technique extracts the time domain(TD)and frequency domain(FD)features from the sEMG signals and is fused.In addition,the EAAA-HDLGR technique exploits the hybrid deep learning(HDL)model for gait recognition.At last,an EAAA-based hyperparameter optimizer is applied for the HDL model,which is mainly derived from the quasi-oppositional based learning(QOBL)concept,showing the novelty of the work.A brief classifier outcome of the EAAA-HDLGR technique is examined under diverse aspects,and the results indicate improving the EAAA-HDLGR technique.The results imply that the EAAA-HDLGR technique accomplishes improved results with the inclusion of EAAA on gait recognition.展开更多
Organic light-emitting diodes(OLEDs)are driven by injected charges from an anode and a cathode.The low and high work function metals are necessary for the effective injection of electrons and holes,respectively.Here,w...Organic light-emitting diodes(OLEDs)are driven by injected charges from an anode and a cathode.The low and high work function metals are necessary for the effective injection of electrons and holes,respectively.Here,we introduce a fully novel design concept using organic semiconductor heterojunctions(OSHJs)as the charge injectors for achieving highly efficient OLEDs,regardless of the work functions of the electrodes.In contrast to traditional injected charges from the electrodes,the injected charges originate from the OSHJs.The device performance was shown to be significantly improved in efficiency and stability compared to conventional OLEDs.Attractively,the OLEDs based on OSHJs as charge injectors still exhibited an impressive performance when the low work function Al was replaced by air-and chemistry-stable high work function metals,such as Au,Ag,and Cu,as the cathode contact,which has been suggested to be difficult in conventional OLEDs.This concept challenges the conventional design approach for the injection of charges and allows for the realization of practical applications of OLEDs with respect to high efficiency,selectable electrodes,and a long lifetime.展开更多
Microcavity photon dynamics in curved space is an emerging interesting area at the crossing point of nanophotonics,chaotic science,and non-Euclidean geometry.We report the sharp difference between the regular and chao...Microcavity photon dynamics in curved space is an emerging interesting area at the crossing point of nanophotonics,chaotic science,and non-Euclidean geometry.We report the sharp difference between the regular and chaotic motions of cavity photons subjected to the varying space curvature.While the island modes of regular motion rise in the phase diagram in the curved space,the chaotic modes show special mechanisms to adapt to the space curvature,including the fast diffusion of ray dynamics,and the localization and hybridization of the Husimi wavepackets among different periodic orbits.These observations are unique effects enabled by the combination of the chaotic trajectory,the wave nature of light,and the non-Euclidean orbital motion,and therefore make the system a versatile optical simulator for chaotic science under quantum mechanics in curved space-time.展开更多
Organic light-emitting transistors(OLETs)are miniaturized electroluminescent devices,and they simultaneously integrate the dual functionality of switching in organicfield-effect transistors and emission in organic ligh...Organic light-emitting transistors(OLETs)are miniaturized electroluminescent devices,and they simultaneously integrate the dual functionality of switching in organicfield-effect transistors and emission in organic light-emitting diodes,which have recently aroused interest from scientists for the next-generation of display applications[1–3].Notably,white organic light-emitting transistors(WOLETs)have gained much attention for their potential applications in sensors,switches,and light sources,including indoor lighting,street lighting andflood lighting[4].Moreover,the Commission Internationale de l’Elcairage(CIE)standard coordinates are precisely defined as(0.33,0.33)of pure white emission,providing a universal reference for evaluating white light accuracy and consistency across lighting and display technologies[5].To meet the requirements of high color-purity,most of the reported white emissive materials and WOLETs have been achieved by rational combination of red,green,blue for three primary colors or blue and orange for two complementary colors emitters[6],such as doping an emitter into an appropriate host and employing the multi-component active layers with a stacked configuration[7].Although a minority of doped electroluminescent devices have the capability of good exciton utilization to realize the white emission,the multi-component active layer is inherently prone to phase separation,which is harmful for the optoelectronic devices[4].Therefore.展开更多
Transient thermal instability represents a significant challenge in generating soliton microcombs.Fast laser sweep can be an efficient method to mitigate thermal instability,but it requires an ultrahigh laser sweep ra...Transient thermal instability represents a significant challenge in generating soliton microcombs.Fast laser sweep can be an efficient method to mitigate thermal instability,but it requires an ultrahigh laser sweep rate for crystalline microresonators with fast thermal relaxation.Here,we engineer a laser sweep waveform to generate AlNon-sapphire soliton microcombs with an intermediate sweep speed(<30 GHz∕μs).Two laser sweep methods with backward plus forward tuning or two-step backward tuning added after the fast forward laser sweep were demonstrated to stabilize solitons.Reducing the soliton number is found to be useful to stabilize solitons in fast laser sweep.The effectiveness of the methods was numerically verified.Our measurements and simulations also reveal the impacts of different thermal relaxation processes occurring at quite different time scales on thermal instability.The requirement of the laser sweep protocols is discussed.展开更多
The kinetic of low-temperature carrier and lattice of lead-halide perovskite is yet to be fully understood.In this work,we investigate the steady-state photoluminescences(PLs)of CsPbI_(3)at the environmental temperatu...The kinetic of low-temperature carrier and lattice of lead-halide perovskite is yet to be fully understood.In this work,we investigate the steady-state photoluminescences(PLs)of CsPbI_(3)at the environmental temperature(Te)ranging from 20 K to 300 K,and observed anomalous behaviors at cryogenic temperatures:The carrier temperature(Tc)of pure CsPbI_(3)exhibits a negative correlation with Te,accompanied by an expansion in Urbach tails of absorption spectra(Abs.)and excessive red-shifts at peak energy of PLs.These phenomena are also observed in those samples containing a certain amount of Cs_(4)PbI_(6),but to a lesser extent and occurs at lower temperatures.It is attributed to the intensified hot phonon bottleneck effect(HPB)in CsPbI_(3)at cryogenic Te,which hinders the energy transfer from hot carriers,via longitudinal optics(LO)phonons to longitudinal acoustic(LA)phonons,to the ambient.For samples under continuous-wave laser excitation,in specific,the barrier induced by the enhanced HPB at low Teprevents the effective thermalization among carriers,LO and LA phonons,which,therefore,form thermally isolated ensembles with different temperatures.At cryogenic Terange,the elevated temperatures of carrier and LO phonon expand the high-energy side of PLs and the low-energy tail of Abs.,respectively.For those samples in which the CsPbI_(3)is mixed with Cs_(4)PbI_(6),the interfacial LO-LO interaction across them provides a bypass for heat dissipation,mitigating the heat accumulation in LO-phonons of CsPbI_(3).The results suggest that a strong HPB effect may break the thermal equilibrium among different branches of phonons in the lattice under certain extreme conditions.展开更多
Quantum dots(QDs) offer an interesting alternative for traditional phosphors in on-chip light-emitting diode(LED) configurations.Earlier studies showed that the spectral efficiency of white LEDs with high color render...Quantum dots(QDs) offer an interesting alternative for traditional phosphors in on-chip light-emitting diode(LED) configurations.Earlier studies showed that the spectral efficiency of white LEDs with high color rendering index(CRI) values could be considerably improved by replacing red-emitting nitride phosphors with narrowband QDs.However,the red QDs in these studies were cadmium-based,which is a restricted element in the EU and certain other countries.The use of InP-based QDs,the most promising Cd-free alternative,is often presented as an inferior solution because of the broader linewidth of these QDs.However,while narrow emission lines are the key to display applications that require a large color gamut,the spectral efficiency penalty of this broader emission is limited for lighting applications.Here,we report efficient,high-CRI white LEDs with an on-chip color converter coating based on red InP/ZnSe QDs and traditional green/yellow powder phosphors.Using InP/ZnSe QDs with a quantum yield of nearly 80% and a full width at half-maximum of 45 nm,we demonstrate high spectral efficiency for white LEDs with very high CRI values.One of the best experimental results in terms of both luminous efficacy and color rendering performance is a white LED with an efficacy of 132 lm/W,and color rendering indices of R_(a)≈90,R9 ≈50 for CCT ≈4000 K.These experimental results are critically compared with theoretical benchmark values for white LEDs with on-chip downconversion from both phosphors and red Cd-based QDs.The various loss mechanisms in the investigated white LEDs are quantified with an accurate simulation model,and the main impediments to an even higher efficacy are identified as the blue LED wall-plug Quantum dots(QDs) offer an interesting alternative for traditional phosphors in on-chip light-emitting diode(LED) configurations.Earlier studies showed that the spectral efficiency of white LEDs with high color rendering index(CRI) values could be considerably improved by replacing red-emitting nitride phosphors wit展开更多
AIM:To assess the efficacy of artificial natural light in preventing incident myopia in primary school-age children.METHODS:This is a prospective,randomized control,intervention study.A total of 1840 students from 39 ...AIM:To assess the efficacy of artificial natural light in preventing incident myopia in primary school-age children.METHODS:This is a prospective,randomized control,intervention study.A total of 1840 students from 39 classes in 4 primary schools in Foshan participated in this study.The whole randomization method was adopted to include classes as a group according to 1:1 randomized control.Classrooms in the control group were illuminated by usual light,and classrooms in the intervention group were illuminated by artificial natural light.All students received uncorrected visual acuity and best-corrected visual acuity measurement,non-cycloplegic autorefraction,ocular biometric examination,slit lamp and strabismus examination.Three-year follow-up,the students underwent same procedures.Myopia was defined as spherical equivalent refraction≤-0.50 D and uncorrected visual acuity<20/20.RESULTS:There were 894 students in the control group and 946 students in the intervention group with a mean±SD age of 7.50±0.53y.The three-year cumulative incidence rate of myopia was 26.4%(207 incident cases among 784 eligible participants at baseline)in the control group and 21.2%(164 incident cases among 774 eligible participants at baseline)in the intervention group[difference of 5.2%(95%CI,3.7%to 10.1%);P=0.035].There was also a significant difference in the three-year change in spherical equivalent refraction for the control group(-0.81 D)compared with the intervention group[-0.63 D;difference of 0.18 D(95%CI,0.08 to 0.28 D);P<0.001].Elongation of axial length was significantly different between in the control group(0.77 mm)and the intervention group[0.72 mm;difference of 0.05 mm(95%CI,0.01 to 0.09 mm);P=0.003].CONCLUSION:Artificial natural light in the classroom of primary schools can result in reducing incidence rate of myopia during a period of three years.展开更多
Gallium oxide(Ga_(2)O_(3)),a novel ultrawide-bandgap(UWBG)semiconductor,has attracted considerable attention owing to its large bandgap of up to 4.9 eV,a high breakdown electric field of 8 MV/cm,and a high Baliga'...Gallium oxide(Ga_(2)O_(3)),a novel ultrawide-bandgap(UWBG)semiconductor,has attracted considerable attention owing to its large bandgap of up to 4.9 eV,a high breakdown electric field of 8 MV/cm,and a high Baliga's figure of merit exceeding 3000[1,2].These remarkable properties strongly support its potential applications in power electronics,extreme environmentresistance devices,and solar-blind detectors[1–3].展开更多
Encapsulation is a widely recognized method for enhancing the stability of colloidal quantum dots (CQDs). However, traditional encapsulation methods for solid-state materials expose encapsulated CQDs to risks such as ...Encapsulation is a widely recognized method for enhancing the stability of colloidal quantum dots (CQDs). However, traditional encapsulation methods for solid-state materials expose encapsulated CQDs to risks such as ligand loss and poor dispersion. Additionally, these encapsulated CQDs still face the risk of aging due to surface ligand bond breakage under high-energy radiation. In this study, we found that quantum dots in solution exhibited enhanced ultraviolet (UV) tolerance compared to their counterparts in solid form under an inert atmosphere. We attribute this enhancement to improved ligand retention and self-healing of quantum dots in solution. Herein, we introduce a novel method for fabricating liquid-encapsulated quantum dot (LEQD) color conversion films. This technique leverages the self-healing capability of ligands in liquid-state quantum dots to enhance the UV and thermal stability of the quantum dot color conversion films. Experimental results demonstrate that LEQD films exhibit better resistance to UV radiation and high temperatures than solid-encapsulated quantum dot (SEQD) color conversion films. After 400 h of exposure to 100 mW blue light-emitting device (LED) light at 60 °C and 90% humidity, the brightness of LEQD film retained 90% of its initial level. This liquid-state quantum dot encapsulation approach offers a promising pathway for developing more durable quantum dot color conversion films.展开更多
Low frequency flicker,high frequency flicker,strong light,strong blue light,infrared,ultraviolet,electromagnetic radiation,ripple flicker and dimming flicker produced by different lamps have negative impact on vision,...Low frequency flicker,high frequency flicker,strong light,strong blue light,infrared,ultraviolet,electromagnetic radiation,ripple flicker and dimming flicker produced by different lamps have negative impact on vision,eyes and health. Negative impact on eyes resulting in myopia or cataract etc: the solution is to remove all the negative factors by applying upright lighting technology and that is optimum to vision,eyes and health.展开更多
Two-dimensional(2D)magnetic materials are essential for the development of the next-generation spintronic technologies.Recently,layered van der Waals(vdW)compound MnBi2Te4(MBT)has attracted great interest,and its 2D s...Two-dimensional(2D)magnetic materials are essential for the development of the next-generation spintronic technologies.Recently,layered van der Waals(vdW)compound MnBi2Te4(MBT)has attracted great interest,and its 2D structure has been reported to host coexisting magnetism and topology.Here,we design several conceptual nanodevices based on MBT monolayer(MBT-ML)and reveal their spin-dependent transport properties by means of the first-principles calculations.The pn-junction diodes and sub-3-nm pin-junction field-effect transistors(FETs)show a strong rectifying effect and a spin filtering effect,with an ideality factor n close to 1 even at a reasonably high temperature.In addition,the pip-and nin-junction FETs give an interesting negative differential resistive(NDR)effect.The gate voltages can tune currents through these FETs in a large range.Furthermore,the MBT-ML has a strong response to light.Our results uncover the multifunctional nature of MBT-ML,pave the road for its applications in diverse next-generation semiconductor spin electric devices.展开更多
Blockchain,a peer-to-peer,controlled,distributed database structure,has the potential to profoundly affect current business transactions in the construction industry through smart contracts,cryptocurrencies,and reliab...Blockchain,a peer-to-peer,controlled,distributed database structure,has the potential to profoundly affect current business transactions in the construction industry through smart contracts,cryptocurrencies,and reliable asset tracking.The construction industry is often criticized for being slow in embracing emerging technologies and not effectively diffusing them through its supply chains.Often,the extensive fragmentation,traditional procurement structures,destructive competition,lack of collaboration and transparency,low-profit margins,and human resources are shown as the main culprits for this.As blockchain technology makes its presence felt strongly in many other industries like finance and banking,this study investigates the preparation of construction supply chains for blockchain technology through an explorative analysis.Empirical data for the study were collected through semistructured interviews with 17 subject experts.Alongside presenting a strengths,weaknesses,opportunities,and threats analysis(SWOT),the study exhibits the requirements for and steps toward a construction supply structure facilitated by blockchain technology.展开更多
We propose a flexible white-light system for high-speed visible-light communication(VLC)applications,which consists of a semipolar blue InGaN/GaN single-quantum-well micro-light-emitting diode(LED)on a flexible substr...We propose a flexible white-light system for high-speed visible-light communication(VLC)applications,which consists of a semipolar blue InGaN/GaN single-quantum-well micro-light-emitting diode(LED)on a flexible substrate pumping green CsPbBr3 perovskite quantum-dot(PQD)paper in nanostructure form and red CdSe QD paper.The highest bandwidth for CsPbBr3 PQD paper,229 MHz,is achieved with a blue micro-LED pumping source and a high data transmission rate of 400 Mbps;this is very promising for VLC application.An 817 MHz maximum bandwidth and a 1.5 Gbps transmission speed are attained by the proposed semipolar blue micro-LEDs.The proposed flexible white light system and the high-bandwidth PQD paper could pave the way for VLC wearable devices.展开更多
Proposed and demonstrated is a novel computer modeling method for high power light emitting diodes(LEDs). It contains geometrical structure and optical property of high power LED as well as LED dies definition with it...Proposed and demonstrated is a novel computer modeling method for high power light emitting diodes(LEDs). It contains geometrical structure and optical property of high power LED as well as LED dies definition with its spatial and angular distribution. Merits and non-merits of traditional modeling methods when applied to high power LEDs based on secondary optical design are discussed. Two commercial high power LEDs are simulated using the proposed computer modeling method. Correlation coefficient is proposed to compare and analyze the simulation results and manufacturing specifications. The source model is precisely demonstrated by obtaining above 99% in correlation coefficient with different surface incident angle intervals.展开更多
基金Ministry of Science and Technology,Taiwan,China(MOST)(107-2221-E-009-113-MY3,105-2221-E-009-112-MY3)Strait Postdoctoral Foundation of Fujian Province of China
文摘Full-color displays based on micro light-emitting diodes(μLEDs) can be fabricated on monolithic epitaxial wafers. Nanoring(NR) structures were fabricated on a green LED epitaxial wafer; the color of NR-μLEDs was tuned from green to blue through strain relaxation. An Al_2O_3 layer was deposited on the sidewall of NR-μLEDs,which improved the photoluminescence intensity by 143.7%. Coupling with the exposed multiple quantum wells through nonradiative resonant energy transfer, red quantum dots were printed to NR-μLEDs for a full-color display. To further improve the color purity of the red light, a distributed Bragg reflector is developed to reuse the excitation light.
基金Ministry of Science and Technology,Taiwan,China(107-2221-E-009-113-MY3,108-2221-E-009-113-MY3)National Natural Science Foundation of China(11904302)+1 种基金Hsinchu Science Park Bureau,Ministry of Science and Technology,Taiwan,China(108A08B)Major Science and Technology Project of Xiamen,China(3502Z20191015)。
文摘Red-green-blue(RGB)full-color micro light-emitting diodes(μ-LEDs)fabricated from semipolar(20-21)wafers,with a quantum-dot photoresist color-conversion layer,were demonstrated.The semipolar(20-21)In Ga N/Ga Nμ-LEDs were fabricated on large(4 in.)patterned sapphire substrates by orientation-controlled epitaxy.The semipolarμ-LEDs showed a 3.2 nm peak wavelength shift and a 14.7%efficiency droop under 200 A∕cm2injected current density,indicating significant amelioration of the quantum-confined Stark effect.Because of the semipolarμ-LEDs’emission-wavelength stability,the RGB pixel showed little color shift with current density and achieved a wide color gamut(114.4%NTSC space and 85.4%Rec.2020).
基金supported by the National Natural Science Foundation of China (11904302)the Fundamental Research Funds for the Central Universities (Grant No.20720190005)+1 种基金the Major Science and Technology Project of Xiamen in China (3502Z20191015)Hong Kong University of Science and Technology-Foshan Joint Research Program (FSUST19-FYTRI11)
文摘Augmented reality(AR)and virtual reality(VR)are two novel display technologies that are under updates.The essential feature of AR/VR is the full-color display that requires high pixel densities.To generate three-color pixels,the fluorescent color conversion layer inevitably includes green and red pixels.To fabricate such sort of display kits,inkjet printing is a promising way to position the color conversion layers.In this review article,the progress of AR/VR technologies is first reviewed,and in succession,the state of the art of inkjet printing,as well as two key issues-the optimization of ink and the reduction of coffee-ring effects,are introduced.Finally,some potential problems associated with the color converting layer are highlighted.
基金supported by the National Natural Science Foundation of China (51472051, 61275178, 61378080 and 61705042)Shanghai Sailing Program (16YF1400700)
文摘Silicon(Si)has become the most promising material for monolithic integrated photonic circuits with a wide range of scientific and industrial applications.A variety of Si photonic components,such as optical waveguides,optical modulators and photodetectors,have been successfully demonstrated,however,silicon lasers have not yet been achieved due to the low efficiency of Si emission.In 2000,Pavesi et al.[1]reported the first observation of
基金supported by the Federal Program'Priority 2030'and NSFC(Project 62350610272)A.K.Samusev acknowledges Deutsche Forschungsgemeinschaft-project No.529710370。
文摘Deeply subwavelength lasers(or nanolasers)are highly demanded for compact on-chip bioimaging and sensing at the nanoscale.One of the main obstacles for the development of single-particle nanolasers with all three dimensions shorter than the emitting wavelength in the visible range is the high lasing thresholds and the resulting overheating.Here we ex-ploit exciton-polariton condensation and mirror-image Mie modes in a cuboid CsPbBr3 nanoparticle to achieve coherent emission at the visible wavelength of around 0.53μm from its ultra-small(≈0.007μm3 or≈λ3/20)semiconductor nanocav-ity.The polaritonic nature of the emission from the nanocavity localized in all three dimensions is proven by direct com-parison with corresponding one-dimensional and two-dimensional waveguiding systems with similar material parameters.Such a deeply subwavelength nanolaser is enabled not only by the high values for exciton binding energy(≈35 meV),re-fractive index(>2.5 at low temperature),and luminescence quantum yield of CsPbBr3,but also by the optimization of po-laritons condensation on the Mie resonances with quality factors improved by the metallic substrate.Moreover,the key parameters for optimal lasing conditions are intermode free spectral range and phonons spectrum in CsPbBr3,which govern polaritons condensation path.Such chemically synthesized colloidal CsPbBr3 nanolasers can be potentially de-posited on arbitrary surfaces,which makes them a versatile tool for integration with various on-chip systems.
基金supported by a grant from the Korea Health Technology R&D Project through the KoreaHealth Industry Development Institute (KHIDI)funded by the Ministry of Health&Welfare,Republic of Korea (grant number:HI21C1831)the Soonchunhyang University Research Fund.
文摘Gait is a biological typical that defines the method by that people walk.Walking is the most significant performance which keeps our day-to-day life and physical condition.Surface electromyography(sEMG)is a weak bioelectric signal that portrays the functional state between the human muscles and nervous system to any extent.Gait classifiers dependent upon sEMG signals are extremely utilized in analysing muscle diseases and as a guide path for recovery treatment.Several approaches are established in the works for gait recognition utilizing conventional and deep learning(DL)approaches.This study designs an Enhanced Artificial Algae Algorithm with Hybrid Deep Learning based Human Gait Classification(EAAA-HDLGR)technique on sEMG signals.The EAAA-HDLGR technique extracts the time domain(TD)and frequency domain(FD)features from the sEMG signals and is fused.In addition,the EAAA-HDLGR technique exploits the hybrid deep learning(HDL)model for gait recognition.At last,an EAAA-based hyperparameter optimizer is applied for the HDL model,which is mainly derived from the quasi-oppositional based learning(QOBL)concept,showing the novelty of the work.A brief classifier outcome of the EAAA-HDLGR technique is examined under diverse aspects,and the results indicate improving the EAAA-HDLGR technique.The results imply that the EAAA-HDLGR technique accomplishes improved results with the inclusion of EAAA on gait recognition.
基金the National Natural Science Foundation of China(51333007,91433201)the Ministry of Science and Technology of China(973 program No.2013CB834805)the Foundation of Jilin Research Council(2012ZDGG001)for the support of this research.
文摘Organic light-emitting diodes(OLEDs)are driven by injected charges from an anode and a cathode.The low and high work function metals are necessary for the effective injection of electrons and holes,respectively.Here,we introduce a fully novel design concept using organic semiconductor heterojunctions(OSHJs)as the charge injectors for achieving highly efficient OLEDs,regardless of the work functions of the electrodes.In contrast to traditional injected charges from the electrodes,the injected charges originate from the OSHJs.The device performance was shown to be significantly improved in efficiency and stability compared to conventional OLEDs.Attractively,the OLEDs based on OSHJs as charge injectors still exhibited an impressive performance when the low work function Al was replaced by air-and chemistry-stable high work function metals,such as Au,Ag,and Cu,as the cathode contact,which has been suggested to be difficult in conventional OLEDs.This concept challenges the conventional design approach for the injection of charges and allows for the realization of practical applications of OLEDs with respect to high efficiency,selectable electrodes,and a long lifetime.
基金supported by the National Key R&D Program of China(Grant No.2023YFA1407100)the National Natural Science Foundation of China(Grant Nos.12074303,and 11804267)+2 种基金the Shaanxi Key Science and Technology Innovation Team Project(Grant No.2021TD-56)the Sichuan Science and Technology Program(Grant No.2022NSFSC1811)the Xiaomi Young Scholar Program。
文摘Microcavity photon dynamics in curved space is an emerging interesting area at the crossing point of nanophotonics,chaotic science,and non-Euclidean geometry.We report the sharp difference between the regular and chaotic motions of cavity photons subjected to the varying space curvature.While the island modes of regular motion rise in the phase diagram in the curved space,the chaotic modes show special mechanisms to adapt to the space curvature,including the fast diffusion of ray dynamics,and the localization and hybridization of the Husimi wavepackets among different periodic orbits.These observations are unique effects enabled by the combination of the chaotic trajectory,the wave nature of light,and the non-Euclidean orbital motion,and therefore make the system a versatile optical simulator for chaotic science under quantum mechanics in curved space-time.
基金supported by the National Natural Science Foundation of China(52233010,52103245,22021002,and 22305252)the CAS Project for Young Scientists in Basic Research(YSBR053)+4 种基金the Beijing National Laboratory for Molecular Sciences(BNLMS-CXXM-202012)China Postdoctoral Science Foundation(2023M733555)Postdoctoral Fellowship Program of CPSF(GZB20230771)the International Cooperation Program of the Chinese Academy of Sciences(121111KYSB20200004)The authors also acknowledge Dr.Xun Tang(Kyushu University)for the optical discussion and Zhenling Liu(Institute of Chemistry,Chinese Academy of Sciences)for the ESP calculated.
文摘Organic light-emitting transistors(OLETs)are miniaturized electroluminescent devices,and they simultaneously integrate the dual functionality of switching in organicfield-effect transistors and emission in organic light-emitting diodes,which have recently aroused interest from scientists for the next-generation of display applications[1–3].Notably,white organic light-emitting transistors(WOLETs)have gained much attention for their potential applications in sensors,switches,and light sources,including indoor lighting,street lighting andflood lighting[4].Moreover,the Commission Internationale de l’Elcairage(CIE)standard coordinates are precisely defined as(0.33,0.33)of pure white emission,providing a universal reference for evaluating white light accuracy and consistency across lighting and display technologies[5].To meet the requirements of high color-purity,most of the reported white emissive materials and WOLETs have been achieved by rational combination of red,green,blue for three primary colors or blue and orange for two complementary colors emitters[6],such as doping an emitter into an appropriate host and employing the multi-component active layers with a stacked configuration[7].Although a minority of doped electroluminescent devices have the capability of good exciton utilization to realize the white emission,the multi-component active layer is inherently prone to phase separation,which is harmful for the optoelectronic devices[4].Therefore.
基金National Natural Science Foundation of China(62022080,62175127,62250071)National Key Research and Development Program of China(2021YFB2801200)+3 种基金Tsinghua Initiative Scientific Research Program(20211080080,20221080069)Youth Innovation Promotion Association of the Chinese Academy of Sciences(2023123)SJTU-Pinghu Institute of Intelligent OptoelectronicsTsinghua-Toyota Joint Research Fund。
文摘Transient thermal instability represents a significant challenge in generating soliton microcombs.Fast laser sweep can be an efficient method to mitigate thermal instability,but it requires an ultrahigh laser sweep rate for crystalline microresonators with fast thermal relaxation.Here,we engineer a laser sweep waveform to generate AlNon-sapphire soliton microcombs with an intermediate sweep speed(<30 GHz∕μs).Two laser sweep methods with backward plus forward tuning or two-step backward tuning added after the fast forward laser sweep were demonstrated to stabilize solitons.Reducing the soliton number is found to be useful to stabilize solitons in fast laser sweep.The effectiveness of the methods was numerically verified.Our measurements and simulations also reveal the impacts of different thermal relaxation processes occurring at quite different time scales on thermal instability.The requirement of the laser sweep protocols is discussed.
基金supported by the National Natural Science Foundation of China(Nos.62374142,12175189 and 11904302)External Cooperation Program of Fujian(No.2022I0004)+1 种基金Fundamental Research Funds for the Central Universities(Nos.20720190005 and 20720220085)Major Science and Technology Project of Xiamen in China(No.3502Z20191015)。
文摘The kinetic of low-temperature carrier and lattice of lead-halide perovskite is yet to be fully understood.In this work,we investigate the steady-state photoluminescences(PLs)of CsPbI_(3)at the environmental temperature(Te)ranging from 20 K to 300 K,and observed anomalous behaviors at cryogenic temperatures:The carrier temperature(Tc)of pure CsPbI_(3)exhibits a negative correlation with Te,accompanied by an expansion in Urbach tails of absorption spectra(Abs.)and excessive red-shifts at peak energy of PLs.These phenomena are also observed in those samples containing a certain amount of Cs_(4)PbI_(6),but to a lesser extent and occurs at lower temperatures.It is attributed to the intensified hot phonon bottleneck effect(HPB)in CsPbI_(3)at cryogenic Te,which hinders the energy transfer from hot carriers,via longitudinal optics(LO)phonons to longitudinal acoustic(LA)phonons,to the ambient.For samples under continuous-wave laser excitation,in specific,the barrier induced by the enhanced HPB at low Teprevents the effective thermalization among carriers,LO and LA phonons,which,therefore,form thermally isolated ensembles with different temperatures.At cryogenic Terange,the elevated temperatures of carrier and LO phonon expand the high-energy side of PLs and the low-energy tail of Abs.,respectively.For those samples in which the CsPbI_(3)is mixed with Cs_(4)PbI_(6),the interfacial LO-LO interaction across them provides a bypass for heat dissipation,mitigating the heat accumulation in LO-phonons of CsPbI_(3).The results suggest that a strong HPB effect may break the thermal equilibrium among different branches of phonons in the lattice under certain extreme conditions.
文摘Quantum dots(QDs) offer an interesting alternative for traditional phosphors in on-chip light-emitting diode(LED) configurations.Earlier studies showed that the spectral efficiency of white LEDs with high color rendering index(CRI) values could be considerably improved by replacing red-emitting nitride phosphors with narrowband QDs.However,the red QDs in these studies were cadmium-based,which is a restricted element in the EU and certain other countries.The use of InP-based QDs,the most promising Cd-free alternative,is often presented as an inferior solution because of the broader linewidth of these QDs.However,while narrow emission lines are the key to display applications that require a large color gamut,the spectral efficiency penalty of this broader emission is limited for lighting applications.Here,we report efficient,high-CRI white LEDs with an on-chip color converter coating based on red InP/ZnSe QDs and traditional green/yellow powder phosphors.Using InP/ZnSe QDs with a quantum yield of nearly 80% and a full width at half-maximum of 45 nm,we demonstrate high spectral efficiency for white LEDs with very high CRI values.One of the best experimental results in terms of both luminous efficacy and color rendering performance is a white LED with an efficacy of 132 lm/W,and color rendering indices of R_(a)≈90,R9 ≈50 for CCT ≈4000 K.These experimental results are critically compared with theoretical benchmark values for white LEDs with on-chip downconversion from both phosphors and red Cd-based QDs.The various loss mechanisms in the investigated white LEDs are quantified with an accurate simulation model,and the main impediments to an even higher efficacy are identified as the blue LED wall-plug Quantum dots(QDs) offer an interesting alternative for traditional phosphors in on-chip light-emitting diode(LED) configurations.Earlier studies showed that the spectral efficiency of white LEDs with high color rendering index(CRI) values could be considerably improved by replacing red-emitting nitride phosphors wit
基金Guangdong Basic and Applied Basic Research Foundation(No.2019B1515120011)Medical Research,Foshan Health and Wellness Department(No.20220374).
文摘AIM:To assess the efficacy of artificial natural light in preventing incident myopia in primary school-age children.METHODS:This is a prospective,randomized control,intervention study.A total of 1840 students from 39 classes in 4 primary schools in Foshan participated in this study.The whole randomization method was adopted to include classes as a group according to 1:1 randomized control.Classrooms in the control group were illuminated by usual light,and classrooms in the intervention group were illuminated by artificial natural light.All students received uncorrected visual acuity and best-corrected visual acuity measurement,non-cycloplegic autorefraction,ocular biometric examination,slit lamp and strabismus examination.Three-year follow-up,the students underwent same procedures.Myopia was defined as spherical equivalent refraction≤-0.50 D and uncorrected visual acuity<20/20.RESULTS:There were 894 students in the control group and 946 students in the intervention group with a mean±SD age of 7.50±0.53y.The three-year cumulative incidence rate of myopia was 26.4%(207 incident cases among 784 eligible participants at baseline)in the control group and 21.2%(164 incident cases among 774 eligible participants at baseline)in the intervention group[difference of 5.2%(95%CI,3.7%to 10.1%);P=0.035].There was also a significant difference in the three-year change in spherical equivalent refraction for the control group(-0.81 D)compared with the intervention group[-0.63 D;difference of 0.18 D(95%CI,0.08 to 0.28 D);P<0.001].Elongation of axial length was significantly different between in the control group(0.77 mm)and the intervention group[0.72 mm;difference of 0.05 mm(95%CI,0.01 to 0.09 mm);P=0.003].CONCLUSION:Artificial natural light in the classroom of primary schools can result in reducing incidence rate of myopia during a period of three years.
基金supported by the National Key R&D Program of China(2023YFB3611700)the National Natural Science Foundation of China(92163206,62101044,12321004)。
文摘Gallium oxide(Ga_(2)O_(3)),a novel ultrawide-bandgap(UWBG)semiconductor,has attracted considerable attention owing to its large bandgap of up to 4.9 eV,a high breakdown electric field of 8 MV/cm,and a high Baliga's figure of merit exceeding 3000[1,2].These remarkable properties strongly support its potential applications in power electronics,extreme environmentresistance devices,and solar-blind detectors[1–3].
基金supported by the National Key Research and Development Program of China(Nos.2022YFB3602903,2021YFB3602703,and 2022YFB3606504)Guangdong University Key Laboratory for Advanced Quantum Dot Displays and Lighting(No.2017KSYS007)+4 种基金Shenzhen Key Laboratory for Advanced Quantum Dot Displays and Lighting(No.ZDSYS201707281632549)Shenzhen Science and Technology Program(No.JCYJ20220818100411025)Shenzhen Development and Reform Commission Project(No.XMHT20220114005)High level of special funds(No.G03034K002)Shenzhen Key Laboratory for Deep Subwavelength Scale Photonics(No.ZDSYS20220527171201003).
文摘Encapsulation is a widely recognized method for enhancing the stability of colloidal quantum dots (CQDs). However, traditional encapsulation methods for solid-state materials expose encapsulated CQDs to risks such as ligand loss and poor dispersion. Additionally, these encapsulated CQDs still face the risk of aging due to surface ligand bond breakage under high-energy radiation. In this study, we found that quantum dots in solution exhibited enhanced ultraviolet (UV) tolerance compared to their counterparts in solid form under an inert atmosphere. We attribute this enhancement to improved ligand retention and self-healing of quantum dots in solution. Herein, we introduce a novel method for fabricating liquid-encapsulated quantum dot (LEQD) color conversion films. This technique leverages the self-healing capability of ligands in liquid-state quantum dots to enhance the UV and thermal stability of the quantum dot color conversion films. Experimental results demonstrate that LEQD films exhibit better resistance to UV radiation and high temperatures than solid-encapsulated quantum dot (SEQD) color conversion films. After 400 h of exposure to 100 mW blue light-emitting device (LED) light at 60 °C and 90% humidity, the brightness of LEQD film retained 90% of its initial level. This liquid-state quantum dot encapsulation approach offers a promising pathway for developing more durable quantum dot color conversion films.
文摘Low frequency flicker,high frequency flicker,strong light,strong blue light,infrared,ultraviolet,electromagnetic radiation,ripple flicker and dimming flicker produced by different lamps have negative impact on vision,eyes and health. Negative impact on eyes resulting in myopia or cataract etc: the solution is to remove all the negative factors by applying upright lighting technology and that is optimum to vision,eyes and health.
基金We acknowledge funding from the National Natural Science Foundation of China(Nos.11774079 and 61774059)the Scientific and Technological Innovation Program of Henan Province’s Universities(No.20HASTIT026)+4 种基金the Natural Science Foundation of Henan(No.202300410226)the Natural Science Foundation of Henan Normal University(No.2020PL15)the Henan Overseas Expertise Introduction Center for Discipline Innovation(No.CXJD2019005)the HPCC of HNU.RW acknowledges funding from the US DOE-BES(No.DE-FG02-05ER46237)We thank F.Xue at Tsinghua University,W.Ju and D.Kang at HNUST for helpful discussions.
文摘Two-dimensional(2D)magnetic materials are essential for the development of the next-generation spintronic technologies.Recently,layered van der Waals(vdW)compound MnBi2Te4(MBT)has attracted great interest,and its 2D structure has been reported to host coexisting magnetism and topology.Here,we design several conceptual nanodevices based on MBT monolayer(MBT-ML)and reveal their spin-dependent transport properties by means of the first-principles calculations.The pn-junction diodes and sub-3-nm pin-junction field-effect transistors(FETs)show a strong rectifying effect and a spin filtering effect,with an ideality factor n close to 1 even at a reasonably high temperature.In addition,the pip-and nin-junction FETs give an interesting negative differential resistive(NDR)effect.The gate voltages can tune currents through these FETs in a large range.Furthermore,the MBT-ML has a strong response to light.Our results uncover the multifunctional nature of MBT-ML,pave the road for its applications in diverse next-generation semiconductor spin electric devices.
基金the research project“Toward blockchain-enabled construction supply chains:Potential,requirements and implementation”flinded by the Centre for Digital Built Britain,under Innovate UK Grant No.90066.
文摘Blockchain,a peer-to-peer,controlled,distributed database structure,has the potential to profoundly affect current business transactions in the construction industry through smart contracts,cryptocurrencies,and reliable asset tracking.The construction industry is often criticized for being slow in embracing emerging technologies and not effectively diffusing them through its supply chains.Often,the extensive fragmentation,traditional procurement structures,destructive competition,lack of collaboration and transparency,low-profit margins,and human resources are shown as the main culprits for this.As blockchain technology makes its presence felt strongly in many other industries like finance and banking,this study investigates the preparation of construction supply chains for blockchain technology through an explorative analysis.Empirical data for the study were collected through semistructured interviews with 17 subject experts.Alongside presenting a strengths,weaknesses,opportunities,and threats analysis(SWOT),the study exhibits the requirements for and steps toward a construction supply structure facilitated by blockchain technology.
基金Ministry of Science and Technology,Taiwan(108-2221-E-009-113-MY3,110-2124-M-A49-003-)National Natural Science Foundation of China(11904302)Major Science and Technology Project of Xiamen(3502Z20191015)。
文摘We propose a flexible white-light system for high-speed visible-light communication(VLC)applications,which consists of a semipolar blue InGaN/GaN single-quantum-well micro-light-emitting diode(LED)on a flexible substrate pumping green CsPbBr3 perovskite quantum-dot(PQD)paper in nanostructure form and red CdSe QD paper.The highest bandwidth for CsPbBr3 PQD paper,229 MHz,is achieved with a blue micro-LED pumping source and a high data transmission rate of 400 Mbps;this is very promising for VLC application.An 817 MHz maximum bandwidth and a 1.5 Gbps transmission speed are attained by the proposed semipolar blue micro-LEDs.The proposed flexible white light system and the high-bandwidth PQD paper could pave the way for VLC wearable devices.
基金The"863"Project of National Ministry of Science and Technology(2006AA03A175)
文摘Proposed and demonstrated is a novel computer modeling method for high power light emitting diodes(LEDs). It contains geometrical structure and optical property of high power LED as well as LED dies definition with its spatial and angular distribution. Merits and non-merits of traditional modeling methods when applied to high power LEDs based on secondary optical design are discussed. Two commercial high power LEDs are simulated using the proposed computer modeling method. Correlation coefficient is proposed to compare and analyze the simulation results and manufacturing specifications. The source model is precisely demonstrated by obtaining above 99% in correlation coefficient with different surface incident angle intervals.
