We report a novel double-shelled nanoboxes photocatalyst architecture with tailored interfaces that accelerate quantum efficiency for photocatalytic CO_(2) reduction reaction(CO_(2)RR)via Mo–S bridging bonds sites in...We report a novel double-shelled nanoboxes photocatalyst architecture with tailored interfaces that accelerate quantum efficiency for photocatalytic CO_(2) reduction reaction(CO_(2)RR)via Mo–S bridging bonds sites in S_(v)–In_(2)S_(3)@2H–MoTe_(2).The X-ray absorption near-edge structure shows that the formation of S_(v)–In_(2)S_(3)@2H–MoTe_(2) adjusts the coordination environment via interface engineering and forms Mo–S polarized sites at the interface.The interfacial dynamics and catalytic behavior are clearly revealed by ultrafast femtosecond transient absorption,time-resolved,and in situ diffuse reflectance–Infrared Fourier transform spectroscopy.A tunable electronic structure through steric interaction of Mo–S bridging bonds induces a 1.7-fold enhancement in S_(v)–In_(2)S_(3)@2H–MoTe_(2)(5)photogenerated carrier concentration relative to pristine S_(v)–In_(2)S_(3).Benefiting from lower carrier transport activation energy,an internal quantum efficiency of 94.01%at 380 nm was used for photocatalytic CO_(2)RR.This study proposes a new strategy to design photocatalyst through bridging sites to adjust the selectivity of photocatalytic CO_(2)RR.展开更多
<span style="font-family:Verdana;">A theoretical study of a polysilicon solar cell with a radial junction in </span><span style="font-family:Verdana;">static</span><span ...<span style="font-family:Verdana;">A theoretical study of a polysilicon solar cell with a radial junction in </span><span style="font-family:Verdana;">static</span><span style="font-family:Verdana;"> regime under monochromatic illumination is presented in this paper. The junction radial solar cell geometry is illustrated and described. The carriers’ diffusion equation is established and solved under quasi-neutral base assumption with boundaries conditions and Bessel equations. New analytical expressions of electrons and holes photocurrent density and quantum efficiency are found.</span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;">The wavelength and structural parameters (base radius, </span><span><span style="font-family:Verdana;">base thickness </span><span style="font-family:Verdana;">and</span><span style="font-family:Verdana;"> wavelength) influences on photocurrent density and quantum </span></span><span style="font-family:Verdana;">efficiency are carried out and examined.</span></span></span></span>展开更多
It is well known that cyan-emitting phosphors play a very important role in full-spectrum white LEDs.A large number of cyan-emitting phosphors have been reported in the past few years,however,most of them can only be ...It is well known that cyan-emitting phosphors play a very important role in full-spectrum white LEDs.A large number of cyan-emitting phosphors have been reported in the past few years,however,most of them can only be effectively excited by near-ultraviolet light.There are very few cyan-emitting phosphors that can be intensively excited by blue light(440 and 470 nm).Here,a novel blue-light excitable cyan-emitting phosphor BaLu_(1.95)Ce_(0.05)Al_(2)Ga_(2)SiO_(12)with excellent performance is reported.The cyan phosphor has a cubic structure in space group Ia3^(-)d with a=1.205379(3)nm,which can be easily obtained through a solid-state reaction pathway.The emission peak of the cyan phosphor is located at 500 nm and its internal quantum efficiency is as high as 90.01%when excited at 455 nm at 25℃.The cyan phosphor exhibits superior resistance against thermal quenching of luminescence,and its intensity at 125℃is as strong as 92.14%of the intensity at room temperature.Meanwhile,it also shows an outstanding resistance against water,where its luminescence intensity is hardly changed after being immersed in pure water for 528 h.The white LED lamp prepared by employing the obtained BaLu_(1.95)-Ce_(0.05)Al_(2)Ga_(2)SiO_(12)as cyan phosphor displays remarkable optical properties with CCT=4441 K,Ra=93.7,CRI=90.4 and CIE 1931(x,y)as(x=0.3648,y=0.3752).The experimental results demonstrate that BaLu_(1.95)Ce_(0.05)Al_(2)Ga_(2)SiO_(12)is a promising cyan-emitting phosphor with great application potential in full-spectrum white LEDs.展开更多
Quantum efficiency is a critical piece of information of a quantum emitter and regulates the emitter’s fluorescence decay dynamics in an optical environment through the Purcell effect.Here,we present a simple way to ...Quantum efficiency is a critical piece of information of a quantum emitter and regulates the emitter’s fluorescence decay dynamics in an optical environment through the Purcell effect.Here,we present a simple way to experimentally probe fluorescence quantum efficiency of single dibenzoterrylene molecules embedded in a thin anthracene microcrystal obtained through a co-sublimation process.In particular,we correlate the fluorescence lifetime change of single dibenzoterrylene molecules with the variation of the matrix thickness due to natural sublimation.With the identification of the molecule emission dipole orientation,we could deduce the near-unity intrinsic quantum efficiency of dibenzoterrylene molecules in the anthracene matrix.展开更多
The monocrystalline silicon is a promising material that could be used in solar cells that convert light into electricity. Although the cost of ordinary silicon (Si) solar cells has decreased significantly over the pa...The monocrystalline silicon is a promising material that could be used in solar cells that convert light into electricity. Although the cost of ordinary silicon (Si) solar cells has decreased significantly over the past two decades, the conversion efficiency of these cells has remained relatively high. While solar cells have a great potential as a device of renewable energy, the high cost they incur per Watt continues to be a significant barrier to their widespread implementation. As a consequence, it is vital to conduct research into alternate materials that may be used in the construction of solar cells. The heterojunction solar cell (HJSC), which is based on n-type zinc oxide (n-ZnO) and p-type silicon (p-Si), is one of the numerous alternatives of the typical Si single homojunction solar cell. There are many deficiencies that can be found in the published research on n-ZnO/p-Si heterojunction solar cell. Inconsistencies in the stated value of open circuit voltage (V<sub>oc</sub>) of the solar cell are one example of deficiency. The absence of a full theoretical study to evaluate the potential of the solar cell structure is another deficiency that can be found in these researches. A lower value of experimentally obtained V<sub>OC</sub> in comparison to the theoretical prediction based on the band-gap between n-ZnO and p-Si. There needs to be more consensus among scientists regarding the optimal conditions for the growth of zinc oxide. Many software’s are available for simulating and optimizing the solar cells based on these parameters. For this purpose, in this dissertation, I provide computational results relevant to n-ZnO/p-Si HJSC to overcome deficiencies that have been identified. While modeling and simulating the potential of the solar cell structure with AFORS-HET, it is essential to consider the constraints that exist in the real world. AFORS-HET was explicitly designed to mimic the multilayer solar cell arrangement. In AFORS-HET, we can add up to seven layers for solar cell layout. By using this software, we can figure out the open circuit voltage (V<sub>OC</sub>), the short circuit current (J<sub>SC</sub>), the quantum efficiency (QE, %), the heterojunction energy band structure, and the power conversion efficiency (PCE).展开更多
Photoluminescence(PL) spectra of two different green InGaN/GaN multiple quantum well(MQW) samples S1 and S2,respectively with a higher growth temperature and a lower growth temperature of InGaN well layers are analyze...Photoluminescence(PL) spectra of two different green InGaN/GaN multiple quantum well(MQW) samples S1 and S2,respectively with a higher growth temperature and a lower growth temperature of InGaN well layers are analyzed over a wide temperature range of 6 K-3 30 K and an excitation power range of 0.001 mW-75 mW.The excitation power-dependent PL peak energy and linewidth at 6 K show that in an initial excitation power range,the emission process of the MQW is dominated simultaneously by the combined effects of the carrier scattering and Coulomb screening for both the samples,and both the carrier scattering effect and the Coulomb screening effect are stronger for S2 than those for S1;in the highest excitation power range,the emission process of the MQWs is dominated by the filling effect of the high-energy localized states for S1,and by the Coulomb screening effect for S2.The behaviors can be attributed to the fact that sample S2 should have a higher amount of In content in the InGaN well layers than S1 because of the lower growth temperature,and this results in a stronger component fluctuation-induced potential fluctuation and a stronger well/barrier lattice mismatchinduced quantum-confined Stark effect.This explanation is also supported by other relevant measurements of the samples,such as temperature-dependent peak energy and excitation-power-dependent internal quantum efficiency.展开更多
Based on the deterministic secure quantum communication,we present a novel quantum dialogue protocol without information leakage over the collective noise channel.The logical qubits and four-qubit decoherence-free sta...Based on the deterministic secure quantum communication,we present a novel quantum dialogue protocol without information leakage over the collective noise channel.The logical qubits and four-qubit decoherence-free states are introduced for resisting against collective-dephasing noise,collective-rotation noise and all kinds of unitary collective noise,respectively.Compared with the existing similar protocols,the analyses on security and information-theoretical efficiency show that the proposed protocol is more secure and efficient.展开更多
The conversion of sunlight into electricity via photovoltaics presents tremendous opportunities for the generation of renewable energy. However, solar cells still face several challenges and limitations to further red...The conversion of sunlight into electricity via photovoltaics presents tremendous opportunities for the generation of renewable energy. However, solar cells still face several challenges and limitations to further reduce manufacturing costs and increase module efficiency. Photon management is paramount to increase the efficiency of the mainstream silicon-based cell and always includes a suitable antireflection coating (ARC) structure to decrease the reflectance (R) at the top surface. We propose a novel triple-layer anti-reflective coating (TLAR) consisting of three layers sandwiched between the upper cover (glass) and the substrate (silicon). The inner three layers are graded refractive index material (GIM) as an active layer, titanium dioxide (TiO<sub>2</sub>), and zinc sulfide (ZnS), respectively. The optical properties of the TLAR have been investigated using the transfer matrix method (TMM). The results of using GIM as the active medium lead to the reflection decaying to the minimum value, and the transmittance reaching the maximum values at a specific wavelength range. The proposed triple-layer anti-reflective coating (TLAR) structure presents a promising solution for enhancing the efficiency of solar cells. Its unique design and utilization of graded refractive index material (GIM) as the active layer make it a novel and innovative approach that holds great potential for advancing solar cell technology.展开更多
CO_2 conversion via photocatalysis is a potential solution to address global warming and energy shortage.Photocatalysis can directly utilize the inexhaustible sunlight as an energy source to catalyze the reduction of ...CO_2 conversion via photocatalysis is a potential solution to address global warming and energy shortage.Photocatalysis can directly utilize the inexhaustible sunlight as an energy source to catalyze the reduction of CO_2 to useful solar fuels such as CO, CH_4, CH_3OH, and C_2H_5OH. Among studied formulations, Cubased photocatalysts are the most attractive for CO_2 conversion because the Cu-based photocatalysts are low-cost and abundance comparing noble metal-based catalysts. In this literature review, a comprehensive summary of recent progress on Cu-based photocatalysts for CO_2 conversion, which includes metallic copper, copper alloy nanoparticles(NPs), copper oxides, and copper sulfides photocatalysts, can be found. This review also included a detailed discussion on the correlations of morphology, structure, and performance for each type of Cu-based catalysts. The reaction mechanisms and possible pathways for productions of various solar fuels were analyzed, which provide insight into the nature of potential active sites for the catalysts. Finally, the current challenges and perspective future research directions were outlined, holding promise to advance Cu-based photocatalysts for CO_2 conversion with much-enhanced energy conversion efficiency and production rates.展开更多
Because of the good thermal stability and superior carrier transport characteristics of formamidinium lead trihalide perovskite HC(NH_2)_2 PbX_3(FAPbX_3), it has been considered to be a better optoelectronic material ...Because of the good thermal stability and superior carrier transport characteristics of formamidinium lead trihalide perovskite HC(NH_2)_2 PbX_3(FAPbX_3), it has been considered to be a better optoelectronic material than conventional CH_3NH_3-PbX_3(MAPbX_3). Herein, we fabricated a FAPbBr_3 microcrystal-based photodetector that exhibited a good responsivity of 4000 A W-1 and external quantum efficiency up to 106% under one-photon excitation, corresponding to the detectivity greater than 1014 Jones. The responsivity is two orders of magnitude higher than that of previously reported formamidinium perovskite photodetectors. Furthermore, the FAPbBr_3 photodetector's responsivity to two-photon absorption with an 800-nm excitation source can reach 0.07 A W^(-1), which is four orders of magnitude higher than that of its MAPbBr_3 counterparts. The response time of this photodetector is less than 1 ms.This study provides solid evidence that FAPbBr_3 can be an excellent candidate for highly sensitive and fast photodetectors.展开更多
We have investigated the factors affecting the current spreading length(CSL) in GaN-based light-emitting diodes(LEDs) by deriving theoretical expressions and performing simulations with APSYS.For mesa-structure LEDs,t...We have investigated the factors affecting the current spreading length(CSL) in GaN-based light-emitting diodes(LEDs) by deriving theoretical expressions and performing simulations with APSYS.For mesa-structure LEDs,the effects of both indium tin oxide(ITO) and n-GaN are taken into account for the first time,and a new Q factor is introduced to explain the effects of different current flow paths on the CSL.The calculations and simulations show that the CSL can be enhanced by increasing the thickness of the ITO layer and resistivity of the n-GaN layer,or by reducing the resistivity of the ITO layer and thickness of the n-GaN layer.The results provide theoretical support for calculating the CSL clearly and directly.For vertical-structure LEDs,the effects of resistivity and thickness of the CSL on the internal quantum efficiency(IQE) have been analyzed.The theoretical expression relating current density and the parameters(resistivity and thickness)of the CSL is obtained,and the results are then verified by simulation.The IQE under different current injection conditions is discussed.The effects of CSL resistivity play a key role at high current injection,and there is an optimal thickness for the largest IQE only at a low current injection.展开更多
Fluorozirconate glass containing Eu^(3+) ions and chloride ions are prepared by a meltquenching method. The luminescence behavior of Eu^(3+) affected by Cl ions is investigated. With increasing Cl ion concentration, t...Fluorozirconate glass containing Eu^(3+) ions and chloride ions are prepared by a meltquenching method. The luminescence behavior of Eu^(3+) affected by Cl ions is investigated. With increasing Cl ion concentration, the luminous intensity of Eu^(3+) is significantly enhanced and the quantum efficiency of fluorozirconate glass is improved. Meanwhile, the intensity parameter ?_2 increases according to the Judd–Ofelt calculation, which indicates the decrease of local symmetry. The average lifetime of Eu^(3+) increases by introducing the Cl ions. Moreover, we find two kinds of sites for Eu^(3+)ions in a glass network by analyzing the fluorescence decay. The distribution of Eu^(3+) ions changes with increasing Cl ion concentration.In addition, the excessive Cl ions lead to the separation of the glass phase and the formation of the crystal phase, thus reducing the transmittance dramatically.展开更多
This study investigates two secondary electron emission(SEE)models for photoelectric energy distribution curves f(E_(ph),hγ),B,E_(mean),absolute quantum efficiency(AQE),and the mean escape depth of photo-emitted elec...This study investigates two secondary electron emission(SEE)models for photoelectric energy distribution curves f(E_(ph),hγ),B,E_(mean),absolute quantum efficiency(AQE),and the mean escape depth of photo-emitted electronsλof metals.The proposed models are developed from the density of states and the theories of photo-emission in the vacuum ultraviolet and SEE,where B is the mean probability that an internal photo-emitted electron escapes into vacuum upon reaching the emission surface of the metal,and E_(mean)is the mean energy of photo-emitted electrons measured from vacuum.The formulas for f(E_(ph),hγ),B,λ,E_(mean),and AQE that were obtained were shown to be correct for the cases of Au at hγ=8.1–11.6 eV,Ni at hγ=9.2–11.6 eV,and Cu at hγ=7.7–11.6 eV.The photoelectric cross sections(PCS)calculated here are analyzed,and it was confirmed that the calculated PCS of the electrons in the conduction band of Au at hγ=8.1–11.6eV,Ni at hγ=9.2–11.6 eV,and Cu at hγ=7.7–11.6 eV are correct.展开更多
The optical properties of AlGaN-based quantum well(QW)structure with two coupled thin well layers are investigated by the six-by-six K-P method.Compared with the conventional structure,the new structure,especially the...The optical properties of AlGaN-based quantum well(QW)structure with two coupled thin well layers are investigated by the six-by-six K-P method.Compared with the conventional structure,the new structure,especially the one with lower Al-content in the barrier layer,can enhance the TE-/TM-polarized total spontaneous emission rate due to the strong quantum confinement and wide recombination region.For the conventional QW structure,the reduction of well thickness can lead the degree of polarization(DOP)to decrease and the internal quantum efficiency(IQE)to increase.By using the coupled thin well layers,the DOP for the structure with high Al-content in the barrier layer can be improved,while the DOP will further decrease with low Al-content in the barrier layer.It can be attributed to the band adjustment induced by the combination of barrier height and well layer coupling.The IQE can also be further enhanced to 14.8%-20.5%for various Al-content of barrier layer at J=100 A/cm^(2).In addition,the efficiency droop effect can be expected to be suppressed compared with the conventional structure.展开更多
Colloidal Pb Se nanocrystals(NCs)have gained considerable attention due to their efficient carrier multiplication and emissions across near-infrared and short-wavelength infrared spectral ranges.However,the fast degra...Colloidal Pb Se nanocrystals(NCs)have gained considerable attention due to their efficient carrier multiplication and emissions across near-infrared and short-wavelength infrared spectral ranges.However,the fast degradation of colloidal Pb Se NCs in ambient conditions hampers their widespread applications in infrared optoelectronics.It is well-known that the inorganic thick-shell over core improves the stability of NCs.Here,we present the synthesis of Pb Se/Pb S core/shell NCs showing wide spectral tunability,in which the molar ratio of lead(Pb)and sulfur(S)precursors,and the concentration of sulfur and Pb Se NCs in solvent have a significant effect on the efficient Pb S shell growth.The infrared light-emitting diodes(IR-LEDs)fabricated with the Pb Se/Pb S core/shell NCs exhibit an external quantum efficiency(EQE)of 1.3%at 1280 nm.The ligand exchange to optimize the distance between NCs and chloride treatment are important processes for achieving high performance on Pb Se/Pb S NC-LEDs.Our results provide evidence for the promising potential of Pb Se/Pb S NCs over the wide range of infrared optoelectronic applications.展开更多
We report intrinsic photoconductivity studies on one of the least examined layered compounds,ZrS2.Few-atomic layer ZrS2 field-effect transistors were fabricated on the Si/SiO2 substrate and photoconductivity measureme...We report intrinsic photoconductivity studies on one of the least examined layered compounds,ZrS2.Few-atomic layer ZrS2 field-effect transistors were fabricated on the Si/SiO2 substrate and photoconductivity measurements were performed using both two-and four-terminal configurations under the illumination of 532 nm laser source.We measured photocurrent as a function of the incident optical power at several source-drain(bias)voltages.We observe a significantly large photoconductivity when measured in the multiterminal(four-terminal)configuration compared to that in the two-terminal configuration.For an incident optical power of 90 nW,the estimated photosensitivity and the external quantum efficiency(EQE)measured in two-terminal configuration are 0.5 A/W and 120%,respectively,under a bias voltage of 650 mV.Under the same conditions,the four-terminal measurements result in much higher values for both the photoresponsivity(R)and EQE to 6 A/W and 1400%,respectively.This significant improvement in photoresponsivity and EQE in the four-terminal configuration may have been influenced by the reduction of contact resistance at the metal-semiconductor interface,which greatly impacts the carrier mobility of low conducting materials.This suggests that photoconductivity measurements performed through the two-terminal configuration in previous studies on ZrS2 and other 2D materials have severely underestimated the true intrinsic properties of transition metal dichalcogenides and their remarkable potential for optoelectronic applications.展开更多
Comprehensive Summary Conjugated fused-ring structures have attracted extensive attention due to their high molecular rigidity to restrain excited-state relaxation and non-radiative decay,and further to enhance the lu...Comprehensive Summary Conjugated fused-ring structures have attracted extensive attention due to their high molecular rigidity to restrain excited-state relaxation and non-radiative decay,and further to enhance the luminance efficiency for emissive materials.Herein,we develop a series of donor-acceptor type thermally activated delayed fluorescence(TADF)emitters by introducing fused-ring 5H-benzofuro[3,2-c]carbazole(32BFCz)as electron donating unit.Through optimizing the numbers and structure of donor and acceptor moieties,three compounds named 32BFCzA,mCF3BFCzOXD and dCF3BFCzOXD are designed,which are composed by mono-32BFCz/trifluoromethylpicolinonitrile,penta-BFCz/3-(trifluoromethyl)phenyl)-1,3,4-oxadiazol-2-yl)benzene and penta-32BFCz/3,5-bis(trifluoromethyl)phenyl)-1,3,4-oxadiazol-2-yl)benzene as donor/acceptor groups,respectively.展开更多
Mini-LED backlights,combining color conversion materials with blue mini-LED chips,promise traditional liquid crystal displays(LCDs)with higher luminance,better contrast,and a wider color gamut.However,as color convers...Mini-LED backlights,combining color conversion materials with blue mini-LED chips,promise traditional liquid crystal displays(LCDs)with higher luminance,better contrast,and a wider color gamut.However,as color conversion materials,quantum dots(QDs)are toxic and unstable,whereas commercially available inorganic phosphors are too big in size to combine with small mini-LED chips and also have strong size-dependence of quantum efficiency(QE)and reliability.In this work,we prepare fine-grained Sr_(2)Si_(5)N_(8):Eu^(2+)-based red phosphors with high efficiency and stability by treating commercially available phosphors with ball milling,centrifuging,and acid washing.The particle size of phosphors can be easily controlled by milling speed,and the phosphors with a size varying from 3.5 to 0.7 mm are thus obtained.The samples remain the same QE as the original ones(~80%)even when their particle size is reduced to 3.2-3.5 mm,because they contain fewer surface suspension bond defects.More importantly,SrBaSi_(5)N_(8):Eu^(2+)phosphors show a size-independent thermal quenching behavior and a zero thermal degradation.We demonstrate that red-emitting mini-LEDs can be fabricated by combining the SrBaSi_(5)N_(8):Eu^(2+)red phosphor(3.5 mm in size)with blue mini-LED chips,which show a high external quantum efficiency(EQE)of above 31%and a super-high luminance of 34.3 Mnits.It indicates that fine and high efficiency phosphors can be obtained by the proposed method in this work,and they have great potentials for use in mini-LED displays.展开更多
A research team led by Prof.Pan Jianwei(潘建伟)and Prof.Bao Xiaohui(包小辉)at the University of Science and Technology of China,reported the successful realization of an efficient quantum light-matter interface with s...A research team led by Prof.Pan Jianwei(潘建伟)and Prof.Bao Xiaohui(包小辉)at the University of Science and Technology of China,reported the successful realization of an efficient quantum light-matter interface with sub-second lifetime,which can be used as an elementary unit to extend the distance of quantum communication through quantum repeater.This result was recently published in Nature展开更多
Vertical ZnO nanotube (ZNT) arrays were synthesized onto an indium doped tin oxide (ITO) glass substrate by a simple electrochemical deposition technique followed by a selective etching process. Scanning electron micr...Vertical ZnO nanotube (ZNT) arrays were synthesized onto an indium doped tin oxide (ITO) glass substrate by a simple electrochemical deposition technique followed by a selective etching process. Scanning electron microscopy (SEM) showed formation of well-faceted hexagonal ZNT arrays spreading uniformly over a largearea. X-ray diffraction (XRD) of ZNT layer showed substantially higher intensity for the (0002) diffractionpeak, indicating that the ZnO crystallites were well aligned with their c-axis. Profilometer measurements ofthe ZNT layer showed an average thickness of ～7 μm. Diameter size distribution (DSD) analysis showedthat ZNTs exhibited a narrow diameter size distribution in the range of 65–120 nm and centered at ～75nm. The photoluminescence (PL) spectrum measurement showed violet and blue luminescence peaks thatwere centered at 410 and 480 nm, respectively, indicating the presence of internal defects. Ultra-violet (UV)spectroscopy showed major absorbance peak at ～348 nm, exhibiting an increase in energy gap value of 3.4 eV.By employing the formed ZNTs as the photo-anode for a dye-sensitized solar cell (DSSC), a full-sun conversion efficiency of 1.01% was achieved with a fill factor of 54%. Quantum efficiency studies showed the maximumof incident photon-to-electron conversion efficiency in a visible region located at 520–550 nm range.展开更多
基金the Natural Science Foundation of China(11922415,12274471)Guangdong Basic and Applied Basic Research Foundation(2022A1515011168,2019A1515011718,2019A1515011337)the Key Research and Development Program of Guangdong Province,China(2019B110209003).
文摘We report a novel double-shelled nanoboxes photocatalyst architecture with tailored interfaces that accelerate quantum efficiency for photocatalytic CO_(2) reduction reaction(CO_(2)RR)via Mo–S bridging bonds sites in S_(v)–In_(2)S_(3)@2H–MoTe_(2).The X-ray absorption near-edge structure shows that the formation of S_(v)–In_(2)S_(3)@2H–MoTe_(2) adjusts the coordination environment via interface engineering and forms Mo–S polarized sites at the interface.The interfacial dynamics and catalytic behavior are clearly revealed by ultrafast femtosecond transient absorption,time-resolved,and in situ diffuse reflectance–Infrared Fourier transform spectroscopy.A tunable electronic structure through steric interaction of Mo–S bridging bonds induces a 1.7-fold enhancement in S_(v)–In_(2)S_(3)@2H–MoTe_(2)(5)photogenerated carrier concentration relative to pristine S_(v)–In_(2)S_(3).Benefiting from lower carrier transport activation energy,an internal quantum efficiency of 94.01%at 380 nm was used for photocatalytic CO_(2)RR.This study proposes a new strategy to design photocatalyst through bridging sites to adjust the selectivity of photocatalytic CO_(2)RR.
文摘<span style="font-family:Verdana;">A theoretical study of a polysilicon solar cell with a radial junction in </span><span style="font-family:Verdana;">static</span><span style="font-family:Verdana;"> regime under monochromatic illumination is presented in this paper. The junction radial solar cell geometry is illustrated and described. The carriers’ diffusion equation is established and solved under quasi-neutral base assumption with boundaries conditions and Bessel equations. New analytical expressions of electrons and holes photocurrent density and quantum efficiency are found.</span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;">The wavelength and structural parameters (base radius, </span><span><span style="font-family:Verdana;">base thickness </span><span style="font-family:Verdana;">and</span><span style="font-family:Verdana;"> wavelength) influences on photocurrent density and quantum </span></span><span style="font-family:Verdana;">efficiency are carried out and examined.</span></span></span></span>
基金Project supported by the National Natural Science Foundation of China(11864015,51962005)the Scientific Research Foundation for Universities from the Education Bureau of Jiangxi Province of China(GJJ170490,GJJ180480)。
文摘It is well known that cyan-emitting phosphors play a very important role in full-spectrum white LEDs.A large number of cyan-emitting phosphors have been reported in the past few years,however,most of them can only be effectively excited by near-ultraviolet light.There are very few cyan-emitting phosphors that can be intensively excited by blue light(440 and 470 nm).Here,a novel blue-light excitable cyan-emitting phosphor BaLu_(1.95)Ce_(0.05)Al_(2)Ga_(2)SiO_(12)with excellent performance is reported.The cyan phosphor has a cubic structure in space group Ia3^(-)d with a=1.205379(3)nm,which can be easily obtained through a solid-state reaction pathway.The emission peak of the cyan phosphor is located at 500 nm and its internal quantum efficiency is as high as 90.01%when excited at 455 nm at 25℃.The cyan phosphor exhibits superior resistance against thermal quenching of luminescence,and its intensity at 125℃is as strong as 92.14%of the intensity at room temperature.Meanwhile,it also shows an outstanding resistance against water,where its luminescence intensity is hardly changed after being immersed in pure water for 528 h.The white LED lamp prepared by employing the obtained BaLu_(1.95)-Ce_(0.05)Al_(2)Ga_(2)SiO_(12)as cyan phosphor displays remarkable optical properties with CCT=4441 K,Ra=93.7,CRI=90.4 and CIE 1931(x,y)as(x=0.3648,y=0.3752).The experimental results demonstrate that BaLu_(1.95)Ce_(0.05)Al_(2)Ga_(2)SiO_(12)is a promising cyan-emitting phosphor with great application potential in full-spectrum white LEDs.
基金supported by the National Natural Science Foundation of China(No.11874166)。
文摘Quantum efficiency is a critical piece of information of a quantum emitter and regulates the emitter’s fluorescence decay dynamics in an optical environment through the Purcell effect.Here,we present a simple way to experimentally probe fluorescence quantum efficiency of single dibenzoterrylene molecules embedded in a thin anthracene microcrystal obtained through a co-sublimation process.In particular,we correlate the fluorescence lifetime change of single dibenzoterrylene molecules with the variation of the matrix thickness due to natural sublimation.With the identification of the molecule emission dipole orientation,we could deduce the near-unity intrinsic quantum efficiency of dibenzoterrylene molecules in the anthracene matrix.
文摘The monocrystalline silicon is a promising material that could be used in solar cells that convert light into electricity. Although the cost of ordinary silicon (Si) solar cells has decreased significantly over the past two decades, the conversion efficiency of these cells has remained relatively high. While solar cells have a great potential as a device of renewable energy, the high cost they incur per Watt continues to be a significant barrier to their widespread implementation. As a consequence, it is vital to conduct research into alternate materials that may be used in the construction of solar cells. The heterojunction solar cell (HJSC), which is based on n-type zinc oxide (n-ZnO) and p-type silicon (p-Si), is one of the numerous alternatives of the typical Si single homojunction solar cell. There are many deficiencies that can be found in the published research on n-ZnO/p-Si heterojunction solar cell. Inconsistencies in the stated value of open circuit voltage (V<sub>oc</sub>) of the solar cell are one example of deficiency. The absence of a full theoretical study to evaluate the potential of the solar cell structure is another deficiency that can be found in these researches. A lower value of experimentally obtained V<sub>OC</sub> in comparison to the theoretical prediction based on the band-gap between n-ZnO and p-Si. There needs to be more consensus among scientists regarding the optimal conditions for the growth of zinc oxide. Many software’s are available for simulating and optimizing the solar cells based on these parameters. For this purpose, in this dissertation, I provide computational results relevant to n-ZnO/p-Si HJSC to overcome deficiencies that have been identified. While modeling and simulating the potential of the solar cell structure with AFORS-HET, it is essential to consider the constraints that exist in the real world. AFORS-HET was explicitly designed to mimic the multilayer solar cell arrangement. In AFORS-HET, we can add up to seven layers for solar cell layout. By using this software, we can figure out the open circuit voltage (V<sub>OC</sub>), the short circuit current (J<sub>SC</sub>), the quantum efficiency (QE, %), the heterojunction energy band structure, and the power conversion efficiency (PCE).
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51672163 and 51872167)the Major Research Plan of the National Natural Science Foundation of China(Grant No.91433112)。
文摘Photoluminescence(PL) spectra of two different green InGaN/GaN multiple quantum well(MQW) samples S1 and S2,respectively with a higher growth temperature and a lower growth temperature of InGaN well layers are analyzed over a wide temperature range of 6 K-3 30 K and an excitation power range of 0.001 mW-75 mW.The excitation power-dependent PL peak energy and linewidth at 6 K show that in an initial excitation power range,the emission process of the MQW is dominated simultaneously by the combined effects of the carrier scattering and Coulomb screening for both the samples,and both the carrier scattering effect and the Coulomb screening effect are stronger for S2 than those for S1;in the highest excitation power range,the emission process of the MQWs is dominated by the filling effect of the high-energy localized states for S1,and by the Coulomb screening effect for S2.The behaviors can be attributed to the fact that sample S2 should have a higher amount of In content in the InGaN well layers than S1 because of the lower growth temperature,and this results in a stronger component fluctuation-induced potential fluctuation and a stronger well/barrier lattice mismatchinduced quantum-confined Stark effect.This explanation is also supported by other relevant measurements of the samples,such as temperature-dependent peak energy and excitation-power-dependent internal quantum efficiency.
基金Supported by the Foundation and Frontier Research Program of Chongqing Science and Technology Commission of China under Grant No cstc2016jcyjA0571
文摘Based on the deterministic secure quantum communication,we present a novel quantum dialogue protocol without information leakage over the collective noise channel.The logical qubits and four-qubit decoherence-free states are introduced for resisting against collective-dephasing noise,collective-rotation noise and all kinds of unitary collective noise,respectively.Compared with the existing similar protocols,the analyses on security and information-theoretical efficiency show that the proposed protocol is more secure and efficient.
文摘The conversion of sunlight into electricity via photovoltaics presents tremendous opportunities for the generation of renewable energy. However, solar cells still face several challenges and limitations to further reduce manufacturing costs and increase module efficiency. Photon management is paramount to increase the efficiency of the mainstream silicon-based cell and always includes a suitable antireflection coating (ARC) structure to decrease the reflectance (R) at the top surface. We propose a novel triple-layer anti-reflective coating (TLAR) consisting of three layers sandwiched between the upper cover (glass) and the substrate (silicon). The inner three layers are graded refractive index material (GIM) as an active layer, titanium dioxide (TiO<sub>2</sub>), and zinc sulfide (ZnS), respectively. The optical properties of the TLAR have been investigated using the transfer matrix method (TMM). The results of using GIM as the active medium lead to the reflection decaying to the minimum value, and the transmittance reaching the maximum values at a specific wavelength range. The proposed triple-layer anti-reflective coating (TLAR) structure presents a promising solution for enhancing the efficiency of solar cells. Its unique design and utilization of graded refractive index material (GIM) as the active layer make it a novel and innovative approach that holds great potential for advancing solar cell technology.
基金financial supports from the National 1000 Young Talents Program of Chinathe National Nature Science Foundation of China (21603078)+1 种基金the National Materials Genome Project (2016YFB0700600)financial support from Research and Education in eNergy, Environment and Water (RENEW)Institute at the University at Buffalo, SUNY
文摘CO_2 conversion via photocatalysis is a potential solution to address global warming and energy shortage.Photocatalysis can directly utilize the inexhaustible sunlight as an energy source to catalyze the reduction of CO_2 to useful solar fuels such as CO, CH_4, CH_3OH, and C_2H_5OH. Among studied formulations, Cubased photocatalysts are the most attractive for CO_2 conversion because the Cu-based photocatalysts are low-cost and abundance comparing noble metal-based catalysts. In this literature review, a comprehensive summary of recent progress on Cu-based photocatalysts for CO_2 conversion, which includes metallic copper, copper alloy nanoparticles(NPs), copper oxides, and copper sulfides photocatalysts, can be found. This review also included a detailed discussion on the correlations of morphology, structure, and performance for each type of Cu-based catalysts. The reaction mechanisms and possible pathways for productions of various solar fuels were analyzed, which provide insight into the nature of potential active sites for the catalysts. Finally, the current challenges and perspective future research directions were outlined, holding promise to advance Cu-based photocatalysts for CO_2 conversion with much-enhanced energy conversion efficiency and production rates.
基金the National Key R@D Program of China (Grant 2017YFA0204800)the National Natural Science Foundation of China (Grant Nos: 21533010, 21321091, 21525315, 91333116 and 21173169) for their financial supports
文摘Because of the good thermal stability and superior carrier transport characteristics of formamidinium lead trihalide perovskite HC(NH_2)_2 PbX_3(FAPbX_3), it has been considered to be a better optoelectronic material than conventional CH_3NH_3-PbX_3(MAPbX_3). Herein, we fabricated a FAPbBr_3 microcrystal-based photodetector that exhibited a good responsivity of 4000 A W-1 and external quantum efficiency up to 106% under one-photon excitation, corresponding to the detectivity greater than 1014 Jones. The responsivity is two orders of magnitude higher than that of previously reported formamidinium perovskite photodetectors. Furthermore, the FAPbBr_3 photodetector's responsivity to two-photon absorption with an 800-nm excitation source can reach 0.07 A W^(-1), which is four orders of magnitude higher than that of its MAPbBr_3 counterparts. The response time of this photodetector is less than 1 ms.This study provides solid evidence that FAPbBr_3 can be an excellent candidate for highly sensitive and fast photodetectors.
基金Project supported by the National High Technology Research and Development Program of China(Grant No.2014AA032608)the National Natural Science Foundation of China(Grant No.61404101)the China Postdoctoral Science Foundation(Grant No.2014M562415)
文摘We have investigated the factors affecting the current spreading length(CSL) in GaN-based light-emitting diodes(LEDs) by deriving theoretical expressions and performing simulations with APSYS.For mesa-structure LEDs,the effects of both indium tin oxide(ITO) and n-GaN are taken into account for the first time,and a new Q factor is introduced to explain the effects of different current flow paths on the CSL.The calculations and simulations show that the CSL can be enhanced by increasing the thickness of the ITO layer and resistivity of the n-GaN layer,or by reducing the resistivity of the ITO layer and thickness of the n-GaN layer.The results provide theoretical support for calculating the CSL clearly and directly.For vertical-structure LEDs,the effects of resistivity and thickness of the CSL on the internal quantum efficiency(IQE) have been analyzed.The theoretical expression relating current density and the parameters(resistivity and thickness)of the CSL is obtained,and the results are then verified by simulation.The IQE under different current injection conditions is discussed.The effects of CSL resistivity play a key role at high current injection,and there is an optimal thickness for the largest IQE only at a low current injection.
基金supported by the National High Technology Research and Development Program of China(Grant No.2013AA014201)the Natural Science Foundation of Tianjin,China(Grant Nos.14JCZDJC31200,15JCYBJC16700,and 15JCYBJC16800)+1 种基金the National Key Foundation for Exploring Scientific Instrument of China(Grant No.2014YQ120351)the International Cooperation Program from Science and Technology of Tianjin,China(Grant No.14RCGHGX00872)
文摘Fluorozirconate glass containing Eu^(3+) ions and chloride ions are prepared by a meltquenching method. The luminescence behavior of Eu^(3+) affected by Cl ions is investigated. With increasing Cl ion concentration, the luminous intensity of Eu^(3+) is significantly enhanced and the quantum efficiency of fluorozirconate glass is improved. Meanwhile, the intensity parameter ?_2 increases according to the Judd–Ofelt calculation, which indicates the decrease of local symmetry. The average lifetime of Eu^(3+) increases by introducing the Cl ions. Moreover, we find two kinds of sites for Eu^(3+)ions in a glass network by analyzing the fluorescence decay. The distribution of Eu^(3+) ions changes with increasing Cl ion concentration.In addition, the excessive Cl ions lead to the separation of the glass phase and the formation of the crystal phase, thus reducing the transmittance dramatically.
基金supported by the National Natural Science Foundation of China (No.11873013)
文摘This study investigates two secondary electron emission(SEE)models for photoelectric energy distribution curves f(E_(ph),hγ),B,E_(mean),absolute quantum efficiency(AQE),and the mean escape depth of photo-emitted electronsλof metals.The proposed models are developed from the density of states and the theories of photo-emission in the vacuum ultraviolet and SEE,where B is the mean probability that an internal photo-emitted electron escapes into vacuum upon reaching the emission surface of the metal,and E_(mean)is the mean energy of photo-emitted electrons measured from vacuum.The formulas for f(E_(ph),hγ),B,λ,E_(mean),and AQE that were obtained were shown to be correct for the cases of Au at hγ=8.1–11.6 eV,Ni at hγ=9.2–11.6 eV,and Cu at hγ=7.7–11.6 eV.The photoelectric cross sections(PCS)calculated here are analyzed,and it was confirmed that the calculated PCS of the electrons in the conduction band of Au at hγ=8.1–11.6eV,Ni at hγ=9.2–11.6 eV,and Cu at hγ=7.7–11.6 eV are correct.
基金Project supported by the National Natural Science Foundation of China(Grant No.61874168)the Jiangsu Province I-U-R Cooperation Project,China(Grant No.BY2019114)the Nantong Science and Technology Project,China(Grant No.JC2019006)。
文摘The optical properties of AlGaN-based quantum well(QW)structure with two coupled thin well layers are investigated by the six-by-six K-P method.Compared with the conventional structure,the new structure,especially the one with lower Al-content in the barrier layer,can enhance the TE-/TM-polarized total spontaneous emission rate due to the strong quantum confinement and wide recombination region.For the conventional QW structure,the reduction of well thickness can lead the degree of polarization(DOP)to decrease and the internal quantum efficiency(IQE)to increase.By using the coupled thin well layers,the DOP for the structure with high Al-content in the barrier layer can be improved,while the DOP will further decrease with low Al-content in the barrier layer.It can be attributed to the band adjustment induced by the combination of barrier height and well layer coupling.The IQE can also be further enhanced to 14.8%-20.5%for various Al-content of barrier layer at J=100 A/cm^(2).In addition,the efficiency droop effect can be expected to be suppressed compared with the conventional structure.
基金Project supported by the National Key Research and Development Program of China(Grant No.2016YFB0401702)the National Natural Science Foundation of China(Grant Nos.61674074 and 61405089)+6 种基金Development and Reform Commission of Shenzhen Project,China(Grant No.[2017]1395)Shenzhen Peacock Team Project,China(Grant No.KQTD2016030111203005)Shenzhen Key Laboratory for Advanced Quantum Dot Displays and Lighting,China(Grant No.ZDSYS201707281632549)Guangdong Province’s Key R&D Program:Micro-LED Display and Ultra-high Brightness Micro-display Technology,China(Grant No.2019B010925001)Guangdong University Key Laboratory for Advanced Quantum Dot Displays and Lighting,China(Grant No.2017KSYS007)Distinguished Young Scholar of National Natural Science Foundation of Guangdong,China(Grant No.2017B030306010)the start-up fund from Southern University of Science and Technology,Shenzhen,China
文摘Colloidal Pb Se nanocrystals(NCs)have gained considerable attention due to their efficient carrier multiplication and emissions across near-infrared and short-wavelength infrared spectral ranges.However,the fast degradation of colloidal Pb Se NCs in ambient conditions hampers their widespread applications in infrared optoelectronics.It is well-known that the inorganic thick-shell over core improves the stability of NCs.Here,we present the synthesis of Pb Se/Pb S core/shell NCs showing wide spectral tunability,in which the molar ratio of lead(Pb)and sulfur(S)precursors,and the concentration of sulfur and Pb Se NCs in solvent have a significant effect on the efficient Pb S shell growth.The infrared light-emitting diodes(IR-LEDs)fabricated with the Pb Se/Pb S core/shell NCs exhibit an external quantum efficiency(EQE)of 1.3%at 1280 nm.The ligand exchange to optimize the distance between NCs and chloride treatment are important processes for achieving high performance on Pb Se/Pb S NC-LEDs.Our results provide evidence for the promising potential of Pb Se/Pb S NCs over the wide range of infrared optoelectronic applications.
基金N.R.P.acknowledged NSF-PREM through NSFDMR-1826886,HBCU-UP Excellence in research NSFDMR-1900692A portion of this work was performed at the National High Magnetic Field Laboratory,which is supported by the National Science Foundation Cooperative Agreement No.DMR-1644779+1 种基金the State of Florida.This work was performed,in part,at the Center for Nanoscale Materials,a U.S.Department of Energy Office of Science User Facilitysupported by the U.S.Department of Energy,Office of Science,under Contract No.DE-AC02-06CH11357.
文摘We report intrinsic photoconductivity studies on one of the least examined layered compounds,ZrS2.Few-atomic layer ZrS2 field-effect transistors were fabricated on the Si/SiO2 substrate and photoconductivity measurements were performed using both two-and four-terminal configurations under the illumination of 532 nm laser source.We measured photocurrent as a function of the incident optical power at several source-drain(bias)voltages.We observe a significantly large photoconductivity when measured in the multiterminal(four-terminal)configuration compared to that in the two-terminal configuration.For an incident optical power of 90 nW,the estimated photosensitivity and the external quantum efficiency(EQE)measured in two-terminal configuration are 0.5 A/W and 120%,respectively,under a bias voltage of 650 mV.Under the same conditions,the four-terminal measurements result in much higher values for both the photoresponsivity(R)and EQE to 6 A/W and 1400%,respectively.This significant improvement in photoresponsivity and EQE in the four-terminal configuration may have been influenced by the reduction of contact resistance at the metal-semiconductor interface,which greatly impacts the carrier mobility of low conducting materials.This suggests that photoconductivity measurements performed through the two-terminal configuration in previous studies on ZrS2 and other 2D materials have severely underestimated the true intrinsic properties of transition metal dichalcogenides and their remarkable potential for optoelectronic applications.
基金the National Natural Science Foundation of China(Nos.91833304 and 61761136013).
文摘Comprehensive Summary Conjugated fused-ring structures have attracted extensive attention due to their high molecular rigidity to restrain excited-state relaxation and non-radiative decay,and further to enhance the luminance efficiency for emissive materials.Herein,we develop a series of donor-acceptor type thermally activated delayed fluorescence(TADF)emitters by introducing fused-ring 5H-benzofuro[3,2-c]carbazole(32BFCz)as electron donating unit.Through optimizing the numbers and structure of donor and acceptor moieties,three compounds named 32BFCzA,mCF3BFCzOXD and dCF3BFCzOXD are designed,which are composed by mono-32BFCz/trifluoromethylpicolinonitrile,penta-BFCz/3-(trifluoromethyl)phenyl)-1,3,4-oxadiazol-2-yl)benzene and penta-32BFCz/3,5-bis(trifluoromethyl)phenyl)-1,3,4-oxadiazol-2-yl)benzene as donor/acceptor groups,respectively.
基金This work is supported by the National Natural Science Foundation of China(Nos.51832005 and 52172157)the Fundamental Research Funds for the Central Universities(No.20720200075)Fujian Provincial Science and Technology Project(Nos.2020I0002 and 2021J01042).
文摘Mini-LED backlights,combining color conversion materials with blue mini-LED chips,promise traditional liquid crystal displays(LCDs)with higher luminance,better contrast,and a wider color gamut.However,as color conversion materials,quantum dots(QDs)are toxic and unstable,whereas commercially available inorganic phosphors are too big in size to combine with small mini-LED chips and also have strong size-dependence of quantum efficiency(QE)and reliability.In this work,we prepare fine-grained Sr_(2)Si_(5)N_(8):Eu^(2+)-based red phosphors with high efficiency and stability by treating commercially available phosphors with ball milling,centrifuging,and acid washing.The particle size of phosphors can be easily controlled by milling speed,and the phosphors with a size varying from 3.5 to 0.7 mm are thus obtained.The samples remain the same QE as the original ones(~80%)even when their particle size is reduced to 3.2-3.5 mm,because they contain fewer surface suspension bond defects.More importantly,SrBaSi_(5)N_(8):Eu^(2+)phosphors show a size-independent thermal quenching behavior and a zero thermal degradation.We demonstrate that red-emitting mini-LEDs can be fabricated by combining the SrBaSi_(5)N_(8):Eu^(2+)red phosphor(3.5 mm in size)with blue mini-LED chips,which show a high external quantum efficiency(EQE)of above 31%and a super-high luminance of 34.3 Mnits.It indicates that fine and high efficiency phosphors can be obtained by the proposed method in this work,and they have great potentials for use in mini-LED displays.
文摘A research team led by Prof.Pan Jianwei(潘建伟)and Prof.Bao Xiaohui(包小辉)at the University of Science and Technology of China,reported the successful realization of an efficient quantum light-matter interface with sub-second lifetime,which can be used as an elementary unit to extend the distance of quantum communication through quantum repeater.This result was recently published in Nature
基金Department of Science and Technology (DST), Government of India was gratefully acknowledged for their financial support under the NATAG program monitored by Dr. G. Sundararajan
文摘Vertical ZnO nanotube (ZNT) arrays were synthesized onto an indium doped tin oxide (ITO) glass substrate by a simple electrochemical deposition technique followed by a selective etching process. Scanning electron microscopy (SEM) showed formation of well-faceted hexagonal ZNT arrays spreading uniformly over a largearea. X-ray diffraction (XRD) of ZNT layer showed substantially higher intensity for the (0002) diffractionpeak, indicating that the ZnO crystallites were well aligned with their c-axis. Profilometer measurements ofthe ZNT layer showed an average thickness of ～7 μm. Diameter size distribution (DSD) analysis showedthat ZNTs exhibited a narrow diameter size distribution in the range of 65–120 nm and centered at ～75nm. The photoluminescence (PL) spectrum measurement showed violet and blue luminescence peaks thatwere centered at 410 and 480 nm, respectively, indicating the presence of internal defects. Ultra-violet (UV)spectroscopy showed major absorbance peak at ～348 nm, exhibiting an increase in energy gap value of 3.4 eV.By employing the formed ZNTs as the photo-anode for a dye-sensitized solar cell (DSSC), a full-sun conversion efficiency of 1.01% was achieved with a fill factor of 54%. Quantum efficiency studies showed the maximumof incident photon-to-electron conversion efficiency in a visible region located at 520–550 nm range.
