To fully utilize the resources provided by optical fiber networks,a cross-band quantum light source generating photon pairs,where one photon in a pair is at C band and the other is at O band,is proposed in this work.T...To fully utilize the resources provided by optical fiber networks,a cross-band quantum light source generating photon pairs,where one photon in a pair is at C band and the other is at O band,is proposed in this work.This source is based on spontaneous four-wave mixing(SFWM)in a piece of shallow-ridge silicon waveguide.Theoretical analysis shows that the waveguide dispersion could be tailored by adjusting the ridge width,enabling broadband photon pair generation by SFWM across C band and O band.The spontaneous Raman scattering(SpRS)in silicon waveguides is also investigated experimentally.It shows that there are two regions in the spectrum of generated photons from SpRS,which could be used to achieve cross-band photon pair generation.A chip of shallow-ridge silicon waveguide samples with different ridge widths has been fabricated,through which cross-band photon pair generation is demonstrated experimentally.The experimental results show that the source can be achieved using dispersion-optimized shallow-ridge silicon waveguides.This cross-band quantum light source provides a way to develop new fiber-based quantum communication functions utilizing both C band and O band and extends applications of quantum networks.展开更多
Microring resonators(MRRs)are extensively utilized in photonic chips for generating quantum light sources and enabling high-efficiency nonlinear frequency conversion.However,conventional microrings are typically optim...Microring resonators(MRRs)are extensively utilized in photonic chips for generating quantum light sources and enabling high-efficiency nonlinear frequency conversion.However,conventional microrings are typically optimized for a single specific function,limiting their versatility in multifunctional applications.In this work,we propose a reconfigurable microring resonator architecture designed to accommodate diverse application requirements.By integrating a cascaded Mach–Zehnder interferometer(MZI)as the microring coupler,the design enables independent control of the quality factors for pump,signal and idler photons through two tunable phase shifters.This capability allows for dynamic tuning and optimization of critical performance parameters,including photon-pair generation rate(PGR),spectral purity and single photon heralding efficiency(HE).The proposed structure is implemented on a silicon photonic chip,and experimental results exhibit a wide range of tunability for these parameters,with excellent agreement with theoretical predictions.This flexible and multi-functional design offers a promising pathway for high-performance,highly integrated on-chip quantum information processing systems.展开更多
White light illumination is essential in daily life,however,the substantial amount of blue light it contains can damage human eyes.Therefore,it is important to block this high-energy blue light to protect visual healt...White light illumination is essential in daily life,however,the substantial amount of blue light it contains can damage human eyes.Therefore,it is important to block this high-energy blue light to protect visual health.In this study,yellow-emitting carbon dots(CDs)with a quantum yield exceeding 94%were synthesized using citric acid and urea.These CDs effectively absorb blue light.By incorporating them into polystyrene,multiple films termed CDs-based blue light blocking films(CBFs)were developed,each offering different levels of blue light absorption.These CBFs exhibited excellent transparency and efficient blue light filtering capabilities.This study highlights the potential of high quantum yield CDs,which specifically absorb blue light,as foundational materials for developing light-blocking solutions against highenergy short-wavelength light.展开更多
A mathematical model of quantum noise having much effect on the low light imaging system is set up. To simulate the quantum noise, the random numbers obeying noise distribution must be formed and are weighted on the...A mathematical model of quantum noise having much effect on the low light imaging system is set up. To simulate the quantum noise, the random numbers obeying noise distribution must be formed and are weighted on the basis of the model created. Three uniform random sequences are built by the linear congruential method, of which two are used to form integer number and decimal fraction parts of the new random sequence respectively and the third to shuffle the new sequence. And then a Gauss sequence is formed out of uniform distribution by a function transforming method. It actualizes the simulation in real time of quantum noise in the low light imaging system, where video flow is extracted in real time, the noise summed up and played back side by side with the original video signs by a simulation software.展开更多
The reasons for low output power of AlGalnP Light Emitting Diodes （LEDs） have been analysed. LEDs with AlGaInP material have high internal but low external quantum efficiency and much heat generated inside especiall...The reasons for low output power of AlGalnP Light Emitting Diodes （LEDs） have been analysed. LEDs with AlGaInP material have high internal but low external quantum efficiency and much heat generated inside especially at a large injected current which would reduce both the internal and external quantum efficiencies. Two kinds of LEDs with the same active region but different window layers have been fabricated. The new window layer composed of textured 0.5 μm GaP and thin Indium-Tin-Oxide film has shown that low external quantum efficiency （EQE） has serious impaction on the internal quantum efficiency （IQE）, because the carrier distribution will change with the body temperature increasing due to the heat inside, and the test results have shown the evidence of LEDs with lower output power and bigger wavelength red shift.展开更多
InGaN quantum dot is a promising optoelectronic material, which combines the advantages of low-dimensional and wide-gap semiconductors. The growth of InGaN quantum dots is still not mature, especially the growth by me...InGaN quantum dot is a promising optoelectronic material, which combines the advantages of low-dimensional and wide-gap semiconductors. The growth of InGaN quantum dots is still not mature, especially the growth by metal--organic- vapor phase epitaxy （MOVPE）, which is challenge due to the lack of, itin-situ monitoring tool. In this paper, we reviewed the development of InGaN quantum dot growth by MOVPE, including our work on growth of near-UV, green, and red InGaN quantum dots. In addition, we also introduced the applications of InGaN quantum dots on visible light emitting diodes.展开更多
This paper reviews the recent progress in the synthesis of near-infrared(NIR) lead chalcogenide(PbX;PbX = PbS,PbSe, PbTe) quantum dots(QDs) and their applications in NIR QDs based light emitting diodes(NIR-QLEDs). It ...This paper reviews the recent progress in the synthesis of near-infrared(NIR) lead chalcogenide(PbX;PbX = PbS,PbSe, PbTe) quantum dots(QDs) and their applications in NIR QDs based light emitting diodes(NIR-QLEDs). It summarizes the strategies of how to synthesize high efficiency PbX QDs and how to realize high performance Pb X based NIR-QLEDs.展开更多
MXene(M_(n+1)Xn)is an emerging class of layered two-dimensional(2D)materials,which are derived from their bulk-state MAX phase(M_(n+1)AXn,where M:early transition metal,A:group element 13 and 14,and X:carbon and/or ni...MXene(M_(n+1)Xn)is an emerging class of layered two-dimensional(2D)materials,which are derived from their bulk-state MAX phase(M_(n+1)AXn,where M:early transition metal,A:group element 13 and 14,and X:carbon and/or nitrogen).MXenes have found wide-ranging applications in energy storage devices,sensors,catalysis,etc.owing to their high electronic conductivity and wide range of optical absorption.However,the absence of semiconducting MXenes has limited their applications related to light emission.Research has shown that quantum dots(QDs)derived from MXene(MQDs)not only retain the properties of the parent MXene but also demonstrate significant improvement on light emission and quantum yield(QY).The optical properties and photoluminescence(PL)emission mechanisms of these light-emitting MQDs have not been comprehensively investigated.Recently,work on light-emitting MQDs has shown good progress,and MQDs exhibiting multi-color PL emission along with high QY have been fabricated.The synthesis methods also play a vital role in determining the light emission properties of these MQDs.This review provides an overview of light-emitting MQDs and their synthesis methods,optical properties,and applications in various optical,sensory,and imaging devices.The future prospects of light-emitting MQDs are also discussed to provide an insight that helps to further advance the progress on MQDs.展开更多
Graphene quantum dots （GODs） recently emerge as the new and appealing nanophotocatalyst because of their low-cost, environmental compatibility and the ability to facilitate the charge migration and prolong the charg...Graphene quantum dots （GODs） recently emerge as the new and appealing nanophotocatalyst because of their low-cost, environmental compatibility and the ability to facilitate the charge migration and prolong the charge lifetimes. In this work, a visible photocatalyst of S-doped graphene quantum dots （S-GQDs） was prepared by a facile hydrothermal synthesis using 1,3,6-trinitropyrene and Na2S as precursors. The well crystallization and monodispersity as well as the chemical environment of S-GQDs were characterized by transmission electron microscopy, atom force microscopy and X-ray photoelectron spectrum. A superior photocatalytic performance of S-GQDs was demonstrated for degradation of basic fuchsin under visible light irradiation. Furthermore, the possible photocatalytic mechanism was proposed based on the trapping experiments of active species.展开更多
The InGaN/GaN blue light emitting diode（LED） is numerically investigated using a triangular-shaped quantum well model,which involves analysis on its energy band,carrier concentration,overlap of electron and hole wav...The InGaN/GaN blue light emitting diode（LED） is numerically investigated using a triangular-shaped quantum well model,which involves analysis on its energy band,carrier concentration,overlap of electron and hole wave functions,radiative recombination rate,and internal quantum efficiency.The simulation results reveal that the InGaN/GaN blue light emitting diode with triangular quantum wells exhibits a higher radiative recombination rate than the conventional light emitting diode with rectangular quantum wells due to the enhanced overlap of electron and hole wave functions（above 90%） under the polarization field.Consequently,the efficiency droop is only 18% in the light emitting diode with triangular-shaped quantum wells,which is three times lower than that in a conventional LED.展开更多
In blue quantum dot light emitting diodes(QLEDs),electron injection is insufficient,which would degrade device efficiency and stability.Herein,we employ chlorine passivated ZnO nanoparticles as electron transport laye...In blue quantum dot light emitting diodes(QLEDs),electron injection is insufficient,which would degrade device efficiency and stability.Herein,we employ chlorine passivated ZnO nanoparticles as electron transport layer to facilitate electron injection into QDs effectively.Moreover,it suppresses exciton quenching at the QD/ZnO interface by blocking charge transfer channel.As a result,the maximum external quantum efficiency of blue QLED was increased from 2.55%to 4.60%,and the operation lifetime of blue QLED was nearly 4 times longer than that of the control device.Our work indicates that election injection plays an important role in blue QLED efficiency and stability.展开更多
The present work suggested the use of waste oil palm frond as an alternative precursor for nitrogendoped carbon quantum dots(NCQDs)and proposed a straightforward in-situ hydrothermal method for the preparation of NCQD...The present work suggested the use of waste oil palm frond as an alternative precursor for nitrogendoped carbon quantum dots(NCQDs)and proposed a straightforward in-situ hydrothermal method for the preparation of NCQDs/TiO_(2)nanocomposites.The elemental composition,morphological,structural and optical characteristics of NCQDs/TiO_(2)nanocomposites have been comprehensively investigated.The successful grafting of NCQDs on TiO_(2)matrix was confirmed by the formation of Ti AOAC bond and the electronic coupling between theπ-states of NCQDs and the conduction band of TiO_(2).For the first time,the oil palm frond-derived NCQDs/TiO_(2)was adopted in the photodegradation of methylene blue(MB)under visible-light irradiation.As a result,the photocatalytic efficiency of NCQDs/TiO_(2)nanocomposites(86.16%)was 2.85 times higher than its counterpart TiO_(2)(30.18%).The enhanced performance of nanocomposites was attributed to the pivotal roles of NCQDs serving as electron mediator and visiblelight harvester.Besides,the optimal NCQDs loading was determined at 4 ml while the removal efficiency of NCQDs/TiO_(2)-4 was the highest at a catalyst dosage of 1 g.L^(-1)under alkaline condition.This research work is important as it proposed a new insight to the preparation of biomass-based NCQDs/TiO_(2)using a facile synthetic method,which offers a green and sustainable water remediation technology.展开更多
Quantum dots(QDs)have attracted wide attention from academia and industry because of their advantages such as high emitting efficiency,narrow half-peak width,and continuously adjustable emitting wavelength.QDs light e...Quantum dots(QDs)have attracted wide attention from academia and industry because of their advantages such as high emitting efficiency,narrow half-peak width,and continuously adjustable emitting wavelength.QDs light emitting diodes(QLEDs)are expected to become the next generation commercial display technology.This paper reviews the progress of QLED from physical mechanism,materials,to device engineering.The strategies to improve QLED performance from the perspectives of quantum dot materials and device structures are summarized.展开更多
Energy band structure and interfacial compatibility of heterojunctions are crucial for photocatalysts in promoting photogene rated charge separation and transfer.Here,a combined strategy of vacancy engineering and qua...Energy band structure and interfacial compatibility of heterojunctions are crucial for photocatalysts in promoting photogene rated charge separation and transfer.Here,a combined strategy of vacancy engineering and quantum effect via a facile phosphating process is reported,for the first time,to modulate the energy band structure and the interface of Zn_(x)Cd_(1-x)S/CoP quantum dots(ZCS_(v)/CoP QDs)heterojunction.The combined experimental and theoretical investigation revealed that phosphating process transformed CoO_(x) QDs to CoP QDs,and more importantly,generated considerable amount of sulfur vacancies in ZCS_(v).As a result,a TypeⅡZCS_(v)/CoP QDs heterojunction with compatible interfaces was constructed via in-situ generated P-Zn,P-Cd and S-Co bonds,which facilitated the separation and transfer of the photogenerated charge and thus resulted in a high ability towards hydrogen evolution under visible light(17.53 mmol g^(-1) h^(-1)).This work provides an effective and adaptable strategy to modulate band structure and interfacial compatibility of heterojunctions via vacancy engineering and quantum effect.展开更多
InGaN based light-emitting diodes （LEDs） with dip-shaped quantum wells and conventional rectangular quantum ~lls are numerically investigated by using the APSYS simulation software. It is found that the structure wi...InGaN based light-emitting diodes （LEDs） with dip-shaped quantum wells and conventional rectangular quantum ~lls are numerically investigated by using the APSYS simulation software. It is found that the structure with dip- aped quantum wells shows improved light output power, lower current leakage and less efficiency droop. Based on Lmerical simulation and analysis, these improvements on the electrical and the optical characteristics are attributed ainly to the alleviation of the electrostatic field in dip-shaped InGaN/GaN multiple quantum wells （MQWs）.展开更多
The performance of an InGaN/GaN multiple quantum well（MQW） based visible-light Schottky photodiode（PD）is improved by optimizing the source flow of TEGa during In Ga N QW growth. The samples with five-pair InGaN/Ga...The performance of an InGaN/GaN multiple quantum well（MQW） based visible-light Schottky photodiode（PD）is improved by optimizing the source flow of TEGa during In Ga N QW growth. The samples with five-pair InGaN/GaN MQWs are grown on sapphire substrates by metal organic chemical vapor deposition. From the fabricated Schottky-barrier PDs, it is found that the smaller the TEGa flow, the lower the reverse-bias leakage is. The photocurrent can also be enhanced by depositing the In GaN QWs with using lower TEGa flow. A high responsivity of 1.94 A/W is obtained at 470 nm and -3-V bias in the PD grown with optimized TEGa flow. Analysis results show that the lower TEGa flow used for depositing In Ga N may lead to superior crystalline quality with improved InGaN/GaN interface, and less structural defects related non-radiative recombination centers formed in the MQWs.展开更多
A brief introduction of semiconductor self-assembled quantum dots (QDs) applied in single-photon sources is given. Single QDs in confined quantum optical microcavity systems are reviewed along with their optical prope...A brief introduction of semiconductor self-assembled quantum dots (QDs) applied in single-photon sources is given. Single QDs in confined quantum optical microcavity systems are reviewed along with their optical properties and coupling characteristics. Subsequently, the recent progresses in In(Ga)As QDs systems are summarized including the preparation of quantum light sources, multiple methods for embedding single QDs into different microcavities and the scalability of single-photon emitting wavelength. Particularly, several In(Ga)As QD single-photon devices are surveyed including In(Ga)As QDs coupling with nanowires, InAs QDs coupling with distributed Bragg reflection microcavity and the In(Ga)As QDs coupling with micropillar microcavities. Furthermore, applications in the field of single QDs technology are illustrated, such as the entangled photon emission by spontaneous parametric down conversion, the single-photon quantum storage, the chip preparation of single-photon sources as well as the single-photon resonance-fluorescence measurements.展开更多
Two-dimensional （2D） closed-cavity single quantum well （SQW） and multiple quantum well （MQW） structures are proposed based on the traditional 2D open-cavity SQW structures of photonic crystals. The numerical cal...Two-dimensional （2D） closed-cavity single quantum well （SQW） and multiple quantum well （MQW） structures are proposed based on the traditional 2D open-cavity SQW structures of photonic crystals. The numerical calculation results show that the proposed structures can greatly improve the optical characteristics compared with the traditional structures. It is found that the barrier thickness has a great impact on the optical characteristics of the closed-cavity MQW structures： when the barrier thickness is narrower, each resonant peak which appears in the SQW would split, the number of split times is just equal to the number of wells, and each well in the MQW structures is a travelling-wave-well, similar to the well in the open-cavity SQW structures; when the barrier thickness is wider, there is no effect of spectral splitting, and each well in the MQW structures is a standing-wave-well, just like the well in the closed-cavity SQW. The physical origin of different field distributions and the effect of the spectral splitting are provided.展开更多
In this study, the efficiency droop of an InGaN light-emitting diode （LED） is reduced slgnlncanUy oy using a p-AlGaN/GaN superlattice last quantum barrier. The reduction in efficiency droop is mainly caused by the d...In this study, the efficiency droop of an InGaN light-emitting diode （LED） is reduced slgnlncanUy oy using a p-AlGaN/GaN superlattice last quantum barrier. The reduction in efficiency droop is mainly caused by the decrease of electron current leakage and the increase of hole injection efficiency, which is revealed by investigating the light currents, internal quantum efficiencies, energy band diagrams, carrier concentrations, carrier current densities, and radiative recombination efficiencies of three LED structures with the advanced physical model of semiconductor device （APSYS）.展开更多
Gallium nitride （GaN） based light-emitting diodes （LEDs） with chirped multiple quantum well （MQW） structures have been investigated experimentally and numerically in this paper. Compared to conventional LEDs wit...Gallium nitride （GaN） based light-emitting diodes （LEDs） with chirped multiple quantum well （MQW） structures have been investigated experimentally and numerically in this paper. Compared to conventional LEDs with uniform quantum wells （QWs）, LEDs with chirped MQW structures have better internal quantum efficiency （IQE） and carrier injection efficiency. The droop ratios of LEDs with chirped MQW structures show a remarkable improvement at 600 mA/mm2, reduced down from 28.6% （conventional uniform LEDs） to 23.7% （chirped MQWs-a） and 18.6% （chirped MQWs-b）, respectively. Meanwhile, the peak IQE increases from 76.9% （uniform LEDs） to 83.7% （chirped MQWs-a） and 88.6% （chirped MQWs-b）. The reservoir effect of chirped MQW structures is the significant reason as it could increase hole injection efficiency and radiative recombination. The leakage current and Auger recombination of chirped MQW structures can also be suppressed. Furthermore, the chirped MQWs-b structure with lower potential barriers can enhance the reservoir effect and obtain further improvement of the carrier injection efficiency and radiative recombination, as well as further suppressing efficiency droop.展开更多
基金supported by the Quantum Science and Technology-National Science and Technology Major Project (Grant No.2024ZD0302502 for WZ)the National Natural Science Foundation of China(Grant No.92365210 for WZ)+1 种基金Tsinghua Initiative Scientific Research Program (for WZ)the project of Tsinghua University-Zhuhai Huafa Industrial Share Company Joint Institute for Architecture Optoelectronic Technologies (JIAOT,for YH)。
文摘To fully utilize the resources provided by optical fiber networks,a cross-band quantum light source generating photon pairs,where one photon in a pair is at C band and the other is at O band,is proposed in this work.This source is based on spontaneous four-wave mixing(SFWM)in a piece of shallow-ridge silicon waveguide.Theoretical analysis shows that the waveguide dispersion could be tailored by adjusting the ridge width,enabling broadband photon pair generation by SFWM across C band and O band.The spontaneous Raman scattering(SpRS)in silicon waveguides is also investigated experimentally.It shows that there are two regions in the spectrum of generated photons from SpRS,which could be used to achieve cross-band photon pair generation.A chip of shallow-ridge silicon waveguide samples with different ridge widths has been fabricated,through which cross-band photon pair generation is demonstrated experimentally.The experimental results show that the source can be achieved using dispersion-optimized shallow-ridge silicon waveguides.This cross-band quantum light source provides a way to develop new fiber-based quantum communication functions utilizing both C band and O band and extends applications of quantum networks.
基金Project supported by the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0301500)the National Natural Science Foundation of China(Grant No.62105366)。
文摘Microring resonators(MRRs)are extensively utilized in photonic chips for generating quantum light sources and enabling high-efficiency nonlinear frequency conversion.However,conventional microrings are typically optimized for a single specific function,limiting their versatility in multifunctional applications.In this work,we propose a reconfigurable microring resonator architecture designed to accommodate diverse application requirements.By integrating a cascaded Mach–Zehnder interferometer(MZI)as the microring coupler,the design enables independent control of the quality factors for pump,signal and idler photons through two tunable phase shifters.This capability allows for dynamic tuning and optimization of critical performance parameters,including photon-pair generation rate(PGR),spectral purity and single photon heralding efficiency(HE).The proposed structure is implemented on a silicon photonic chip,and experimental results exhibit a wide range of tunability for these parameters,with excellent agreement with theoretical predictions.This flexible and multi-functional design offers a promising pathway for high-performance,highly integrated on-chip quantum information processing systems.
基金supported by Medical Science and Technology Research Project of Henan Province(Joint Construction Project)(No.LHGJ20200433)National Natural Science Foundation of China(No.52122308)。
文摘White light illumination is essential in daily life,however,the substantial amount of blue light it contains can damage human eyes.Therefore,it is important to block this high-energy blue light to protect visual health.In this study,yellow-emitting carbon dots(CDs)with a quantum yield exceeding 94%were synthesized using citric acid and urea.These CDs effectively absorb blue light.By incorporating them into polystyrene,multiple films termed CDs-based blue light blocking films(CBFs)were developed,each offering different levels of blue light absorption.These CBFs exhibited excellent transparency and efficient blue light filtering capabilities.This study highlights the potential of high quantum yield CDs,which specifically absorb blue light,as foundational materials for developing light-blocking solutions against highenergy short-wavelength light.
文摘A mathematical model of quantum noise having much effect on the low light imaging system is set up. To simulate the quantum noise, the random numbers obeying noise distribution must be formed and are weighted on the basis of the model created. Three uniform random sequences are built by the linear congruential method, of which two are used to form integer number and decimal fraction parts of the new random sequence respectively and the third to shuffle the new sequence. And then a Gauss sequence is formed out of uniform distribution by a function transforming method. It actualizes the simulation in real time of quantum noise in the low light imaging system, where video flow is extracted in real time, the noise summed up and played back side by side with the original video signs by a simulation software.
基金Project supported by the National High Technology Research and Development Program of China(Grant No.2006AA03A121)the National Basic Research Program of China(Grant No.2006CB604900)
文摘The reasons for low output power of AlGalnP Light Emitting Diodes （LEDs） have been analysed. LEDs with AlGaInP material have high internal but low external quantum efficiency and much heat generated inside especially at a large injected current which would reduce both the internal and external quantum efficiencies. Two kinds of LEDs with the same active region but different window layers have been fabricated. The new window layer composed of textured 0.5 μm GaP and thin Indium-Tin-Oxide film has shown that low external quantum efficiency （EQE） has serious impaction on the internal quantum efficiency （IQE）, because the carrier distribution will change with the body temperature increasing due to the heat inside, and the test results have shown the evidence of LEDs with lower output power and bigger wavelength red shift.
基金Project supported by the National Basic Research Program of China(Grant Nos.2013CB632804,2011CB301900,and 2012CB3155605)the National Natural Science Foundation of China(Grant Nos.61176015,61210014,51002085,61321004,61307024,and 61176059)the High Technology Research and Development Program of China(Grant No.2012AA050601)
文摘InGaN quantum dot is a promising optoelectronic material, which combines the advantages of low-dimensional and wide-gap semiconductors. The growth of InGaN quantum dots is still not mature, especially the growth by metal--organic- vapor phase epitaxy （MOVPE）, which is challenge due to the lack of, itin-situ monitoring tool. In this paper, we reviewed the development of InGaN quantum dot growth by MOVPE, including our work on growth of near-UV, green, and red InGaN quantum dots. In addition, we also introduced the applications of InGaN quantum dots on visible light emitting diodes.
基金Project supported by the National Key Research and Development Program,China(Grant Nos.2016YFB0401702 and 2017YFE0120400)the National Natural Science Foundation of China(Grant Nos.61875082 and 61405089)+6 种基金the Guangdong University Key Laboratory for Advanced Quantum Dot Displays and Lighting,China(Grant No.2017KSYS007)the Natural Science Foundation of Guangdong,China(Grant No.2017B030306010)the Guangdong Province’s 2018–2019 Key R&D Program:Environmentally Friendly Quantum Dots Luminescent Materials,China(Grant No.2019B010924001)the Shenzhen Innovation Project,China(Grant Nos.JCYJ20160301113356947 and JSGG20170823160757004)the Shenzhen Peacock Team Project,China(Grant No.KQTD2016030111203005)the Shenzhen Key Laboratory for Advanced Quantum Dot Displays and Lighting,China(Grant No.ZDSYS201707281632549)the Tianjin New Materials Science and Technology Key Project,China(Grant No.16ZXCLGX00040)
文摘This paper reviews the recent progress in the synthesis of near-infrared(NIR) lead chalcogenide(PbX;PbX = PbS,PbSe, PbTe) quantum dots(QDs) and their applications in NIR QDs based light emitting diodes(NIR-QLEDs). It summarizes the strategies of how to synthesize high efficiency PbX QDs and how to realize high performance Pb X based NIR-QLEDs.
基金supported by National Research Foundation of Korea(2019R1A2C1006586).
文摘MXene(M_(n+1)Xn)is an emerging class of layered two-dimensional(2D)materials,which are derived from their bulk-state MAX phase(M_(n+1)AXn,where M:early transition metal,A:group element 13 and 14,and X:carbon and/or nitrogen).MXenes have found wide-ranging applications in energy storage devices,sensors,catalysis,etc.owing to their high electronic conductivity and wide range of optical absorption.However,the absence of semiconducting MXenes has limited their applications related to light emission.Research has shown that quantum dots(QDs)derived from MXene(MQDs)not only retain the properties of the parent MXene but also demonstrate significant improvement on light emission and quantum yield(QY).The optical properties and photoluminescence(PL)emission mechanisms of these light-emitting MQDs have not been comprehensively investigated.Recently,work on light-emitting MQDs has shown good progress,and MQDs exhibiting multi-color PL emission along with high QY have been fabricated.The synthesis methods also play a vital role in determining the light emission properties of these MQDs.This review provides an overview of light-emitting MQDs and their synthesis methods,optical properties,and applications in various optical,sensory,and imaging devices.The future prospects of light-emitting MQDs are also discussed to provide an insight that helps to further advance the progress on MQDs.
基金financial support from the Zhejiang Provincial Natural Science Foundation of China (Nos. LY17B050007, LY15B050006)521 Talent Project of ZSTU
文摘Graphene quantum dots （GODs） recently emerge as the new and appealing nanophotocatalyst because of their low-cost, environmental compatibility and the ability to facilitate the charge migration and prolong the charge lifetimes. In this work, a visible photocatalyst of S-doped graphene quantum dots （S-GQDs） was prepared by a facile hydrothermal synthesis using 1,3,6-trinitropyrene and Na2S as precursors. The well crystallization and monodispersity as well as the chemical environment of S-GQDs were characterized by transmission electron microscopy, atom force microscopy and X-ray photoelectron spectrum. A superior photocatalytic performance of S-GQDs was demonstrated for degradation of basic fuchsin under visible light irradiation. Furthermore, the possible photocatalytic mechanism was proposed based on the trapping experiments of active species.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 61076013,51102003,and 60990313)the National Basic Research Program of China (Grant No. 2012CB619304)the Specialized Research Fund for the Doctoral Program of Higher Education,China (Grant No. 20100001120014)
文摘The InGaN/GaN blue light emitting diode（LED） is numerically investigated using a triangular-shaped quantum well model,which involves analysis on its energy band,carrier concentration,overlap of electron and hole wave functions,radiative recombination rate,and internal quantum efficiency.The simulation results reveal that the InGaN/GaN blue light emitting diode with triangular quantum wells exhibits a higher radiative recombination rate than the conventional light emitting diode with rectangular quantum wells due to the enhanced overlap of electron and hole wave functions（above 90%） under the polarization field.Consequently,the efficiency droop is only 18% in the light emitting diode with triangular-shaped quantum wells,which is three times lower than that in a conventional LED.
基金Project supported by the National Key R&D Program of China(Grant Nos.2016YFB0401702 and 2017YFE0120400)the National Natural Science Foundation of China(Grant Nos.62005114,62005115,and 61875082)+5 种基金Key-Area Research and Development Program of Guangdong Province,China(Grant Nos.2019B010925001 and 2019B010924001)Guangdong University Key Laboratory for Advanced Quantum Dot Displays and Lighting(Grant No.2017KSYS007)Natural Science Foundation of Guangdong Province,China(Grant No.2017B030306010)Guangdong Basic and Applied Basic Research Foundation,China(Grant No.2019A1515110437)Shenzhen Peacock Team Project(Grant No.KQTD2016030111203005)High Level University Fund of Guangdong Province,China(Grant No.G02236004).
文摘In blue quantum dot light emitting diodes(QLEDs),electron injection is insufficient,which would degrade device efficiency and stability.Herein,we employ chlorine passivated ZnO nanoparticles as electron transport layer to facilitate electron injection into QDs effectively.Moreover,it suppresses exciton quenching at the QD/ZnO interface by blocking charge transfer channel.As a result,the maximum external quantum efficiency of blue QLED was increased from 2.55%to 4.60%,and the operation lifetime of blue QLED was nearly 4 times longer than that of the control device.Our work indicates that election injection plays an important role in blue QLED efficiency and stability.
基金the funding provided by Universiti Tunku Abdul Rahman Research fund(IPSR/RMC/UTARRF/2020-C2/C06)Centre for Photonics and Advanced Materials Research(CPAMR,UTAR)for their support。
文摘The present work suggested the use of waste oil palm frond as an alternative precursor for nitrogendoped carbon quantum dots(NCQDs)and proposed a straightforward in-situ hydrothermal method for the preparation of NCQDs/TiO_(2)nanocomposites.The elemental composition,morphological,structural and optical characteristics of NCQDs/TiO_(2)nanocomposites have been comprehensively investigated.The successful grafting of NCQDs on TiO_(2)matrix was confirmed by the formation of Ti AOAC bond and the electronic coupling between theπ-states of NCQDs and the conduction band of TiO_(2).For the first time,the oil palm frond-derived NCQDs/TiO_(2)was adopted in the photodegradation of methylene blue(MB)under visible-light irradiation.As a result,the photocatalytic efficiency of NCQDs/TiO_(2)nanocomposites(86.16%)was 2.85 times higher than its counterpart TiO_(2)(30.18%).The enhanced performance of nanocomposites was attributed to the pivotal roles of NCQDs serving as electron mediator and visiblelight harvester.Besides,the optimal NCQDs loading was determined at 4 ml while the removal efficiency of NCQDs/TiO_(2)-4 was the highest at a catalyst dosage of 1 g.L^(-1)under alkaline condition.This research work is important as it proposed a new insight to the preparation of biomass-based NCQDs/TiO_(2)using a facile synthetic method,which offers a green and sustainable water remediation technology.
基金Project supported by Leading innovation and entrepreneurship team of Zhejiang Province of China (Grant No.2021R01003)Science and Technology Innovation 2025 Major Project of Ningbo (Grant No.2022Z085)+2 种基金Ningbo 3315 Programme (Grant No.2020A-01-B)YONGJIANG Talent Introduction Programme (Grant No.2021A-038-B)Zhujiang Talent Programme (Grant No.2016LJ06C621)。
文摘Quantum dots(QDs)have attracted wide attention from academia and industry because of their advantages such as high emitting efficiency,narrow half-peak width,and continuously adjustable emitting wavelength.QDs light emitting diodes(QLEDs)are expected to become the next generation commercial display technology.This paper reviews the progress of QLED from physical mechanism,materials,to device engineering.The strategies to improve QLED performance from the perspectives of quantum dot materials and device structures are summarized.
基金financially supported by the Taishan Scholar Program of Shandong Province(ts201712046)the Key Research and Development Programme of Shandong Province(2019JZZY010905)+2 种基金the Natural Science Foundation of Shandong Province(ZR2020QB132)the Liaoning BaiQianWan Talents Programthe Royal Society and the Newton Fund(NAF\R1\191294)。
文摘Energy band structure and interfacial compatibility of heterojunctions are crucial for photocatalysts in promoting photogene rated charge separation and transfer.Here,a combined strategy of vacancy engineering and quantum effect via a facile phosphating process is reported,for the first time,to modulate the energy band structure and the interface of Zn_(x)Cd_(1-x)S/CoP quantum dots(ZCS_(v)/CoP QDs)heterojunction.The combined experimental and theoretical investigation revealed that phosphating process transformed CoO_(x) QDs to CoP QDs,and more importantly,generated considerable amount of sulfur vacancies in ZCS_(v).As a result,a TypeⅡZCS_(v)/CoP QDs heterojunction with compatible interfaces was constructed via in-situ generated P-Zn,P-Cd and S-Co bonds,which facilitated the separation and transfer of the photogenerated charge and thus resulted in a high ability towards hydrogen evolution under visible light(17.53 mmol g^(-1) h^(-1)).This work provides an effective and adaptable strategy to modulate band structure and interfacial compatibility of heterojunctions via vacancy engineering and quantum effect.
基金supported by the National Natural Science Foundation of China (Grant No. 50602018)the Science and Technology Program of Guangdong Province of China (Grant Nos. 2010B090400456, 2009B011100003, and 2010A081002002)the Scienceand Technology Program of Guangzhou City, China (Grant No. 2010U1-D00191)
文摘InGaN based light-emitting diodes （LEDs） with dip-shaped quantum wells and conventional rectangular quantum ~lls are numerically investigated by using the APSYS simulation software. It is found that the structure with dip- aped quantum wells shows improved light output power, lower current leakage and less efficiency droop. Based on Lmerical simulation and analysis, these improvements on the electrical and the optical characteristics are attributed ainly to the alleviation of the electrostatic field in dip-shaped InGaN/GaN multiple quantum wells （MQWs）.
基金supported by the Science and Technology Major Project of Guangdong Province,China(Grant Nos.2014B010119003 and 2015B010112001)
文摘The performance of an InGaN/GaN multiple quantum well（MQW） based visible-light Schottky photodiode（PD）is improved by optimizing the source flow of TEGa during In Ga N QW growth. The samples with five-pair InGaN/GaN MQWs are grown on sapphire substrates by metal organic chemical vapor deposition. From the fabricated Schottky-barrier PDs, it is found that the smaller the TEGa flow, the lower the reverse-bias leakage is. The photocurrent can also be enhanced by depositing the In GaN QWs with using lower TEGa flow. A high responsivity of 1.94 A/W is obtained at 470 nm and -3-V bias in the PD grown with optimized TEGa flow. Analysis results show that the lower TEGa flow used for depositing In Ga N may lead to superior crystalline quality with improved InGaN/GaN interface, and less structural defects related non-radiative recombination centers formed in the MQWs.
基金supported by the National Key Technologies R&D Program of China(Grant No.2018YFA0306101)the Key R&D Program of Guangdong Province(Grant No.2018B030329001)+1 种基金the Scientific instrument developing project of the Chinese Academy of Science(Grant No.YJKYYQ20170032)the National Natural Science Foundation of China(Grant No.61505196)
文摘A brief introduction of semiconductor self-assembled quantum dots (QDs) applied in single-photon sources is given. Single QDs in confined quantum optical microcavity systems are reviewed along with their optical properties and coupling characteristics. Subsequently, the recent progresses in In(Ga)As QDs systems are summarized including the preparation of quantum light sources, multiple methods for embedding single QDs into different microcavities and the scalability of single-photon emitting wavelength. Particularly, several In(Ga)As QD single-photon devices are surveyed including In(Ga)As QDs coupling with nanowires, InAs QDs coupling with distributed Bragg reflection microcavity and the In(Ga)As QDs coupling with micropillar microcavities. Furthermore, applications in the field of single QDs technology are illustrated, such as the entangled photon emission by spontaneous parametric down conversion, the single-photon quantum storage, the chip preparation of single-photon sources as well as the single-photon resonance-fluorescence measurements.
基金supported by the National Natural Science Foundation of China (Grant Nos 60577006 and 50774034)the Hunan Provincial Science Foundation of China (Grant No 06JJ20005)
文摘Two-dimensional （2D） closed-cavity single quantum well （SQW） and multiple quantum well （MQW） structures are proposed based on the traditional 2D open-cavity SQW structures of photonic crystals. The numerical calculation results show that the proposed structures can greatly improve the optical characteristics compared with the traditional structures. It is found that the barrier thickness has a great impact on the optical characteristics of the closed-cavity MQW structures： when the barrier thickness is narrower, each resonant peak which appears in the SQW would split, the number of split times is just equal to the number of wells, and each well in the MQW structures is a travelling-wave-well, similar to the well in the open-cavity SQW structures; when the barrier thickness is wider, there is no effect of spectral splitting, and each well in the MQW structures is a standing-wave-well, just like the well in the closed-cavity SQW. The physical origin of different field distributions and the effect of the spectral splitting are provided.
基金Project supported by the National Natural Science Foundation of China(Grant No.61176043)the Special Funds for Provincial Strategic and Emerging Industries Projects of Guangdong Province,China(Grant Nos.2010A081002005,2011A081301003,and 2012A080304016)+2 种基金the First Phase of Construction of Guangdong Research Institute of Semiconductor Lighting Industrial Technology,China(Grant No.2010A081001001)the High Efficiency LED Epitaxy and Chip Structure and Key Technology for Industrialization,China(Grant No.2012A080302002)the Youth Funding of South China Normal University(Grant No.2012KJ018)
文摘In this study, the efficiency droop of an InGaN light-emitting diode （LED） is reduced slgnlncanUy oy using a p-AlGaN/GaN superlattice last quantum barrier. The reduction in efficiency droop is mainly caused by the decrease of electron current leakage and the increase of hole injection efficiency, which is revealed by investigating the light currents, internal quantum efficiencies, energy band diagrams, carrier concentrations, carrier current densities, and radiative recombination efficiencies of three LED structures with the advanced physical model of semiconductor device （APSYS）.
基金supported by the National High Technology Research and Development Program of China(Grant No.2014AA032608)the Key Laboratory for Mechanical Behavior of Material of Xi’an Jiaotong University,China(Grant No.20121201)the Fundamental Research Funds for the Central Universities,China
文摘Gallium nitride （GaN） based light-emitting diodes （LEDs） with chirped multiple quantum well （MQW） structures have been investigated experimentally and numerically in this paper. Compared to conventional LEDs with uniform quantum wells （QWs）, LEDs with chirped MQW structures have better internal quantum efficiency （IQE） and carrier injection efficiency. The droop ratios of LEDs with chirped MQW structures show a remarkable improvement at 600 mA/mm2, reduced down from 28.6% （conventional uniform LEDs） to 23.7% （chirped MQWs-a） and 18.6% （chirped MQWs-b）, respectively. Meanwhile, the peak IQE increases from 76.9% （uniform LEDs） to 83.7% （chirped MQWs-a） and 88.6% （chirped MQWs-b）. The reservoir effect of chirped MQW structures is the significant reason as it could increase hole injection efficiency and radiative recombination. The leakage current and Auger recombination of chirped MQW structures can also be suppressed. Furthermore, the chirped MQWs-b structure with lower potential barriers can enhance the reservoir effect and obtain further improvement of the carrier injection efficiency and radiative recombination, as well as further suppressing efficiency droop.
