As typical quarternary copper-based chalcogenides,Cu–Zn–Sn–S nanocrystals(CZTS NCs)have emerged as a newfashioned electrocatalyst in hydrogen evolution reactions(HERs).Oleylamine(OM),a reducing surfactant and solve...As typical quarternary copper-based chalcogenides,Cu–Zn–Sn–S nanocrystals(CZTS NCs)have emerged as a newfashioned electrocatalyst in hydrogen evolution reactions(HERs).Oleylamine(OM),a reducing surfactant and solvent,plays a significant role in the assisting synthesis of CZTS NCs due to the ligand effect.Herein,we adopted a facile one-pot colloidal method for achieving the structure evolution of CZTS NCs from 2D nanosheets to 1D nanorods assisted through the continuous addition of OM.During the process,the mechanism of OM-induced morphology evolution was further discussed.When merely adding pure 1-dodecanethiol(DDT)as the solvent,the CZTS nanosheets were obtained.As OM was gradually added to the reaction,the CZTS NCs began to grow along the sides of the nanosheets and gradually shrink at the top,followed by the formation of stable nanorods.In acidic electrolytic conditions,the CZTS NCs with 1.0 OM addition display the optimal HER activity with a low overpotential of 561 m V at 10 m A/cm^(2) and a small Tafel slope of 157.6 m V/dec compared with other CZTS samples.The enhancement of HER activity could be attributed to the contribution of the synergistic effect of the diverse crystal facets to the reaction.展开更多
The microstructural, optical, and magnetic properties and room-temperature photoluminescence (PL) ofMn-doped ZnO thin films were studied. The chemical compositions were examined by energy dispersive X-ray spectrosco...The microstructural, optical, and magnetic properties and room-temperature photoluminescence (PL) ofMn-doped ZnO thin films were studied. The chemical compositions were examined by energy dispersive X-ray spectroscopy (EDS) and the charge state of Mn ions in the ZnO:Mn films was characterized by X-ray photoelectronic spectrometry (XPS). From the X-ray diffraction (XRD) data of the samples, it can be found that Mn doping does not change the orientation of ZnO thin films. All the films prepared have a wurtzite structure and grow mainly along the c-axis orientation. The grain size and the residual stress were calculated from the XRD results. The optical transmittance of the film decreases with the increase of manganese content in ZnO. The room-temperature photoluminescence of the films shows that the in- tensity of near band energy (NBE) emission depends strongly on the Mn content. The hysteresis behavior indicates that the films with the Mn content below 9at% are ferromagnetic at room temperature.展开更多
Different concentrations of Mg^(2+) -doped hexagonal phase NaGdF_4:Yb^(3+), Er^(3+)nanocrystals(NCs) were synthesized by a modified solvothermal method. Successful codoping of Mg^(2+)ions in upconversio...Different concentrations of Mg^(2+) -doped hexagonal phase NaGdF_4:Yb^(3+), Er^(3+)nanocrystals(NCs) were synthesized by a modified solvothermal method. Successful codoping of Mg^(2+)ions in upconversion nanoparticles(UCNPs) was supported by XRD, SEM, EDS, and PL analyses. The effects of Mg^(2+)doping on the morphology and the intensity of the upconversion(UC) emission were discussed in detail. It turned out that with the concentration of Mg^(2+)increasing, the morphology of the nanoparticles turn to change gradually and the UC emission was increasing gradually as well. Notably the UC fluorescence intensities of Er^(3+)were gradually improved owing to the codoped Mg^(2+)and then achieved a maximum level as the concentration of Mg^(2+)ions was 60 mol% from the amendment of the crystal structure of β-NaGdF_4:Yb^(3+),Er^(3+)nanoparticles. Moreover, the UC luminescence properties of the rare-earth(Yb3+, Er^(3+)) ions codoped NaGdF_4 nanocrystals were investigated in detail under 980-nm excitation.展开更多
Series devices of ITO/ZnO/ZnO nanorods/MEH-PPV/Al have been fabricated.ITO and ZnO nanorods of some devices are treated by O_(2) plasma.The electroluminescence of different devices is detected under different biases.U...Series devices of ITO/ZnO/ZnO nanorods/MEH-PPV/Al have been fabricated.ITO and ZnO nanorods of some devices are treated by O_(2) plasma.The electroluminescence of different devices is detected under different biases.UV electroluminescence of ZnO nanorods at 380 nm is observed in all the devices.The intensity of 380 nm increases when both ITO and ZnO nanorods are treated.The turn-on voltage of the treated device is lower than that of the non-treated device,and the EL power is enhanced.When the thickness of MEH-PPV is sufficiently thin,only 380 nm electroluminescence,besides a weak defect emission at 760 nm,is detected.The enhancement mechanism of the electroluminescence of the treated devices is discussed.展开更多
Thermo-luminescence (TL) is a kind of luminescence decay measured with varying temperature. In the process of TL the decay parameter itself involves the temperature effect of traps. Thus the trap depth is inseparabl...Thermo-luminescence (TL) is a kind of luminescence decay measured with varying temperature. In the process of TL the decay parameter itself involves the temperature effect of traps. Thus the trap depth is inseparable from the decay parameter. There are two separate peaks in the TL curve of ZnS:Cu,Co if the measurement starts from liquid nitrogen temperature. In the experiment we started from zero Celsius temperature to isolate the deeper traps. We have proposed and realized three methods for simultaneous determination of trap depth and decay parameter based on the quasi-equilibrium model and experimental data. If we treat the case of kinetic order a = 1 as a = 2, the error might be as large as 100%.展开更多
The acceleration ability of electrons in SiO2 and ZnS was compared through the variation of emission intensity based on ZnS : Er electroluminescence during the reverse of polarity of sinusoidal voltage. In order to a...The acceleration ability of electrons in SiO2 and ZnS was compared through the variation of emission intensity based on ZnS : Er electroluminescence during the reverse of polarity of sinusoidal voltage. In order to avoid the influence of work function of electrode, cathodal and anodal materials were ITO (indium tin oxide). The ratio of maximum emission intensity under positive and negative half period is 2.18. This result demonstrates that the electron acceleration ability of SiO2 is 2.18 times stronger than that of ZnS.展开更多
Nanosized long-persistent phosphors SrS:Eu^2+, Dy^3+ were prepared by the hydrothermal method.The samples were characterized by X-ray powder diffraction, transmission electron microscopy, and charge-coupled device ...Nanosized long-persistent phosphors SrS:Eu^2+, Dy^3+ were prepared by the hydrothermal method.The samples were characterized by X-ray powder diffraction, transmission electron microscopy, and charge-coupled device spectrometry.The persistence characteristic was studied using the decay curves.The results showed that the emission intensity decreased sharply with temperature increasing, although the particle size increased.The S2-vacancies caused by oxidization served as shallow traps, and Dy3+ served as deep traps in SrS:Eu^2+, Dy^3+.The afterglow intensity of SrS:Eu^2+, Dy^3+ was higher than that of SrS:Eu2+ prepared at the same temperature.However, the minimization span of initial afterglow with temperature for the former sample was larger than that for the latter.Binary-doped phosphor decayed more slowly than the singly doped one.The afterglow of SrS:Eu^2+, Dy^3+ decayed more quickly with the increase of sintering temperature.展开更多
Sputtering method was used to prepare Ni-Mo alloy electrodes for hydrogen production in alkaline solution. The influences of the working pressure during deposition and the substrate temperature on the electrochemical ...Sputtering method was used to prepare Ni-Mo alloy electrodes for hydrogen production in alkaline solution. The influences of the working pressure during deposition and the substrate temperature on the electrochemical behavior of electrode were characterized by steady-state polarization plot and Tafel polarization curve measurements. And the physical properties of electrodes were characterized by XRD, SEM, AFM and EDS. It is found that the overpotential is significantly influenced by the working pressure which affects critically the electrode surface morphology, and two Tafel regions are observed for each sample. The overpotential value does not change very much with the substrate temperature. The XRD results indicates that the electrodes should be considered nanocrystalline. Thornton model for the microstructure of sputter-deposited electrodes is referred to explain the observed microstructure change.展开更多
A novel rare earth complex Eu(TTA)2(N-HPA)Phen (TTA = thenoyltrifluoroacetone, N-HPA = N-phenylanthranilic acid, and phen = 1,10-phenathroline ), which contains three different ligands, was synthesized. The Eu c...A novel rare earth complex Eu(TTA)2(N-HPA)Phen (TTA = thenoyltrifluoroacetone, N-HPA = N-phenylanthranilic acid, and phen = 1,10-phenathroline ), which contains three different ligands, was synthesized. The Eu complex was blended with poly N-vinylcarbazole (PVK) in different weight ratios and spin coated into films. The luminescence properties of films were investigated and energy transfer between PVK and the complex was discussed. Multilayer structural devices consisting of ITO/PVK: Eu (TTA)2 (N-HPA) phen/BCP/Alq3/Al were fabricated with PVK : Eu (TTA)2(N-HPA) as light-emitting layer. Increasing the concentration of Eu in the PVK thin film would inhibit the emission of PVK to different degrees. Finally, the pure red luminescence of europium( Ⅲ ) was observed when the doping weight ratio was approximately 1 : 5, which indicated an effective energy transfer from PVK to rare earth complex.展开更多
In order to investigate the impedance matching properties of microwave absorbers,the ternary nanocomposites of GO/PANI/Fe3O4(GPF) are prepared via a two-step method,GO/PANI composites are synthesized by dilute polym...In order to investigate the impedance matching properties of microwave absorbers,the ternary nanocomposites of GO/PANI/Fe3O4(GPF) are prepared via a two-step method,GO/PANI composites are synthesized by dilute polymerization in the presence of aniline monomer and GO,and GO/PANI/Fe3O4 is prepared via a co-precipitation method.The obtained nanocomposites are characterized by scanning electron microscopy(SEM),X-ray diffraction(XRD),and Fourier transform infrared spectroscopy(FTIR),respectively.The microwave absorbability reveals enhanced microwave absorption properties compared with GO,PANI,and GO/PANI.The maximum reflection loss of GO/PANI/Fe3O4 is up to-27 dB at 14 GHz with its thickness being 2 mm,and its absorption bandwidths exceeding-10 dB are more than 11.2 GHz with its thickness values being in the range from 1.5 mm-4 mm.It provides that GO/PANI/Fe3O4 can be used as an attractive candidate for microwave absorbers.展开更多
We report on the fabrication and electrical characteristics of Ga-doped ZnO thin film transistors(TFTs).Low Ga-doped(0.7wt%)ZnO thin films were deposited on SiO_(2)/p−Si substrates by rf magnetron sputtering.The GZO T...We report on the fabrication and electrical characteristics of Ga-doped ZnO thin film transistors(TFTs).Low Ga-doped(0.7wt%)ZnO thin films were deposited on SiO_(2)/p−Si substrates by rf magnetron sputtering.The GZO TFTs show a mobility of 1.76 cm2/V⋅s,an on/off ratio of 1.0×10^(6),and a threshold voltage of 35 V.The time−dependent instability of the TFT is studied.The VTH shifts negatively.In addition,the device shows a decrease of the on/off ratio,mainly due to the increase of the off-current.The mechanisms of instability are discussed.展开更多
Small molecule organic photovoltaics(SMPVs) were prepared by utilizing liquid crystalline donor material BTR-Cl and two similar optical bandgap non-fullerene acceptor materials BTP-BO-4 F and Y6.The BTPBO-4 F and Y6 h...Small molecule organic photovoltaics(SMPVs) were prepared by utilizing liquid crystalline donor material BTR-Cl and two similar optical bandgap non-fullerene acceptor materials BTP-BO-4 F and Y6.The BTPBO-4 F and Y6 have the similar optical bandgap and different absorption coefficients.The corresponding binary SMPVs exhibit different short circuit current density(/sc)(20.38 vs.23.24 mA cm^(-2)),and fill factor(FF)(70.77% vs.67.21%).A 14.46% power conversion efficiency(PCE) is acquired in ternary SMPVs with 30 wt% Y6,companied with a JSC of 24.17 mA cm^(-2) a FF of 68.78% and an open circuit voltage(Voc) of 0.87 V.The improvement on PCE of ternary SMPVs should originate from the well trade-off between phase separation and photon harvesting of ternary active layers by incorporating 30 wt% Y6 in acceptors.This work may deliver insight onto the improved performance of SMPVs by superposing the superiorities of binary SMPVs with similar optical bandgap acceptors into one ternary cell.展开更多
In this work, bathocuproine (BCP) and bathophenanthroline (Bphen), commonly used in small-molecule organic solar cells (OSCs), are adopted as the buffer layers to improve the performance of the polymer solar cel...In this work, bathocuproine (BCP) and bathophenanthroline (Bphen), commonly used in small-molecule organic solar cells (OSCs), are adopted as the buffer layers to improve the performance of the polymer solar cells (PSCs) based on poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV): [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) bulk heterojunction. By inserting BCP or Bphen between the active layer and the top cathode, all the performance parameters are dramatically improved. The power conversion efficiency is increased by about 70% and 120% with 5-am BCP and 12-nm Bphen layers, respectively, when compared with that of the devices without any buffer layer. The performance enhancement is attributed to BCP or Bphen (i) increasing the optical field, and hence the absorption in the active layer, (ii) effectively blocking the excitons generated in MEH-PPV from quenching at organic/aluminum (Al) interface due to the large band-gap of BCP or Bphen, which results in a significant reduction in series resistance (Rs), and (iii) preventing damage to the active layer during the metal deposition. Compared with the traditional device using LiF as the buffer layer, the BCP-based devices show a comparable efficiency, while the Bphen-based devices show a much larger efficiency. This is due to the higher electron mobility in Bphen than that in BCP, which facilitates the electron transport and extraction through the buffer layer to the cathode.展开更多
In the past five years,all-inorganic metal halide perovskite(CsPbX3,X=Cl,Br,I)nanocrystals have been intensely studied due to their outstanding optical properties and facile synthesis,which endow them with potential o...In the past five years,all-inorganic metal halide perovskite(CsPbX3,X=Cl,Br,I)nanocrystals have been intensely studied due to their outstanding optical properties and facile synthesis,which endow them with potential optoelectronic applications.In order to optimize their physical and chemical properties,different strategies have been developed to realize the controllable synthesis of CsPbX3 nanocrystals.In this short review,we firstly present a comprehensive and detailed summary of existed synthesis strategies of CsPbX3 nanocrystals and their analogues.Then,we introduce the regulations of several reaction parameters and their effects on the morphologies of CsPbX3 nanocrystals.At the same time,we provide stability improvement methods and representative applications.Finally,we propose the current challenges and future perspectives of the promising materials.展开更多
A yellow phosphor, Ca2BO3CI:Eu2+, is prepared by the high-temperature solid-state method. Under the condition of excitation sources ranging from ultraviolet to visible light, efficient yellow emission can be observe...A yellow phosphor, Ca2BO3CI:Eu2+, is prepared by the high-temperature solid-state method. Under the condition of excitation sources ranging from ultraviolet to visible light, efficient yellow emission can be observed. The emission spectrum shows an asymmetrical single intensive band centred at 573 nm, which corresponds to the 4f65dl→4f7 transition of Eu2+. Eu2+ ions occupy two types of Ca2+ sites in the Ca2BO3C1 lattice and form two corresponding emission centres, respectively, which lead to the asymmetrical emission of Eu2+ in Ca2BO3C1. The emission intensity of Eu2+ in Ca2BO3C1 is influenced by the Eu2+ doping concentration. Concentration quenching is discovered, and its mechanism is verified to be a dipole-dipole interaction. The value of the critical transfer distance is calculated to be 2.166 nm, which is in good agreement with the 2.120 nm value derived from the experimental data.展开更多
In this paper a preliminary investigation of a novel optoelectronic polymer, poly (p-phenylene N-4-n-butylphenyl-N,N-bis- 4-vinylenephenylamine) (PNB), is reported. A single layer structure of ITO/PNB/Al was prepared ...In this paper a preliminary investigation of a novel optoelectronic polymer, poly (p-phenylene N-4-n-butylphenyl-N,N-bis- 4-vinylenephenylamine) (PNB), is reported. A single layer structure of ITO/PNB/Al was prepared via spin-coating of PNB solution as a thin film on the top of an ITO substrate, while aluminum top electrode was vacuum evaporated. Dark current- voltage characteristics of this device showed a typical rectifying behaviour. Photovoltaic response under a monochromatic illumination at 420 nm was observed, with an open circuit voltage of 0.3 V and fill factor of 0.21. Spectral response and optical absorption were found to be matched well. It was also discovered that the device showed a green electroluminescent emission at a forward bias. Turn-on voltage of the device was about 6 V and light output about 22.6 nW at a forward bias of 10 V. The work demonstrated that the PNB material might possess dual exciton sites resulting in a competition for excitons to be either separated or recombined. Both effects were associated with each other, which limited the photovoltaic or electroluminescence to some degrees.展开更多
We introduce a generalized concept of principal state of polarization (PSP) to analyse the piezoelectric polarization controller (PPC) and find each PPC unit can be described by a rotation matrix determined by the...We introduce a generalized concept of principal state of polarization (PSP) to analyse the piezoelectric polarization controller (PPC) and find each PPC unit can be described by a rotation matrix determined by the PSP. Our PPC has three components, each made of a jaw and a piezoelectric actuator with the squeezing direction tilted 0°, 45° and 0°, which are driven by a tunable power supply. We demonstrate that all the polarization rotation angles are linear to driving voltages and the PSP of unit 2 is nearly orthogonal to others which are almost equal. Taking some approximate treatments we obtain the matrix model of our PPC with respect to three driving voltages. The average error of our theoretical model is 1.51°, and the polarization response time is 〈50 μs, which is promising to realize an open-loop control of polarization.展开更多
N-dodecanethiol capped zinc sulfide(Zn S) nanocrystals were synthesized by the one-pot approach and blended with poly(N-vinylcarbazole)(PVK) to fabricate electrical bistable devices. The corresponding devices di...N-dodecanethiol capped zinc sulfide(Zn S) nanocrystals were synthesized by the one-pot approach and blended with poly(N-vinylcarbazole)(PVK) to fabricate electrical bistable devices. The corresponding devices did exhibit electrical bistability and negative differential resistance(NDR) effects. A large ON/OFF current ratio of 104 at negative voltages was obtained by applying different amplitudes of sweeping voltage. The observed conductance switching and the negative differential resistance are attributed to the electric-field-induced charge transfer between the nanocrystals and the polymer,and the charge trapping/detrapping in the nanocrystals.展开更多
基金partially supported by National Natural Science Foundation of China (12274021 and 62075005)。
文摘As typical quarternary copper-based chalcogenides,Cu–Zn–Sn–S nanocrystals(CZTS NCs)have emerged as a newfashioned electrocatalyst in hydrogen evolution reactions(HERs).Oleylamine(OM),a reducing surfactant and solvent,plays a significant role in the assisting synthesis of CZTS NCs due to the ligand effect.Herein,we adopted a facile one-pot colloidal method for achieving the structure evolution of CZTS NCs from 2D nanosheets to 1D nanorods assisted through the continuous addition of OM.During the process,the mechanism of OM-induced morphology evolution was further discussed.When merely adding pure 1-dodecanethiol(DDT)as the solvent,the CZTS nanosheets were obtained.As OM was gradually added to the reaction,the CZTS NCs began to grow along the sides of the nanosheets and gradually shrink at the top,followed by the formation of stable nanorods.In acidic electrolytic conditions,the CZTS NCs with 1.0 OM addition display the optimal HER activity with a low overpotential of 561 m V at 10 m A/cm^(2) and a small Tafel slope of 157.6 m V/dec compared with other CZTS samples.The enhancement of HER activity could be attributed to the contribution of the synergistic effect of the diverse crystal facets to the reaction.
基金Supported by the National Natural Science Foundation of China under Grant Nos 60577020 and 60672004, the National High-Tech Research and Development Program of China under Grant No 2007AA01Z270.
基金supported by the National Natural Science Foundation of China(Nos.10774013,10974013,60978060,and 10804006)the National Natural Science Foundation of China for Distinguished Young Scholars(No.60825407)the Doctor Science Creative Grants of Beijing Jiaotong University(No.141028522)
文摘The microstructural, optical, and magnetic properties and room-temperature photoluminescence (PL) ofMn-doped ZnO thin films were studied. The chemical compositions were examined by energy dispersive X-ray spectroscopy (EDS) and the charge state of Mn ions in the ZnO:Mn films was characterized by X-ray photoelectronic spectrometry (XPS). From the X-ray diffraction (XRD) data of the samples, it can be found that Mn doping does not change the orientation of ZnO thin films. All the films prepared have a wurtzite structure and grow mainly along the c-axis orientation. The grain size and the residual stress were calculated from the XRD results. The optical transmittance of the film decreases with the increase of manganese content in ZnO. The room-temperature photoluminescence of the films shows that the in- tensity of near band energy (NBE) emission depends strongly on the Mn content. The hysteresis behavior indicates that the films with the Mn content below 9at% are ferromagnetic at room temperature.
基金supported by the National High Technology Research and Development Program of China(Grant No.2013AA032205)the Key Project of Beijing Scientific Committee,China(Grant No.D161100003416001)+1 种基金the Fundamental Research Funds for the Central Universities,China(Grant No.2016JBM066)the National Natural Science Foundation of China(Grant Nos.51272022 and 11474018)
文摘Different concentrations of Mg^(2+) -doped hexagonal phase NaGdF_4:Yb^(3+), Er^(3+)nanocrystals(NCs) were synthesized by a modified solvothermal method. Successful codoping of Mg^(2+)ions in upconversion nanoparticles(UCNPs) was supported by XRD, SEM, EDS, and PL analyses. The effects of Mg^(2+)doping on the morphology and the intensity of the upconversion(UC) emission were discussed in detail. It turned out that with the concentration of Mg^(2+)increasing, the morphology of the nanoparticles turn to change gradually and the UC emission was increasing gradually as well. Notably the UC fluorescence intensities of Er^(3+)were gradually improved owing to the codoped Mg^(2+)and then achieved a maximum level as the concentration of Mg^(2+)ions was 60 mol% from the amendment of the crystal structure of β-NaGdF_4:Yb^(3+),Er^(3+)nanoparticles. Moreover, the UC luminescence properties of the rare-earth(Yb3+, Er^(3+)) ions codoped NaGdF_4 nanocrystals were investigated in detail under 980-nm excitation.
基金Supported by the National High-Tech Research and Development Programme of China under Grant No 2007AA01Z270, the National Natural Science Foundation of China under Grant No 60877057 and the Ph.D. S&T Innovation Fund of Beijing Jiaotong University.
基金Supported by the National Basic Research Program of China(2010CB327705)the National Natural Science Foundation of China(10974013 and 51272022)+1 种基金the New Century Excellent Talents in University(NCET-10-0220)the Fundamental Research Funds for the Central Universities(2012JBZ001).
文摘Series devices of ITO/ZnO/ZnO nanorods/MEH-PPV/Al have been fabricated.ITO and ZnO nanorods of some devices are treated by O_(2) plasma.The electroluminescence of different devices is detected under different biases.UV electroluminescence of ZnO nanorods at 380 nm is observed in all the devices.The intensity of 380 nm increases when both ITO and ZnO nanorods are treated.The turn-on voltage of the treated device is lower than that of the non-treated device,and the EL power is enhanced.When the thickness of MEH-PPV is sufficiently thin,only 380 nm electroluminescence,besides a weak defect emission at 760 nm,is detected.The enhancement mechanism of the electroluminescence of the treated devices is discussed.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 10374001, 10434030 and 60576016), the State Key Development Program for Basic Research of China (Grant No 2003CB314707), the Excellent Doctor's Science and Technology Innovation Foundation of Beijing Jiaotong University (Grant No 48011), Russian Foundation of Basic Research (Grant Nos 04-02- 16942 and 02-02-39007).
文摘Thermo-luminescence (TL) is a kind of luminescence decay measured with varying temperature. In the process of TL the decay parameter itself involves the temperature effect of traps. Thus the trap depth is inseparable from the decay parameter. There are two separate peaks in the TL curve of ZnS:Cu,Co if the measurement starts from liquid nitrogen temperature. In the experiment we started from zero Celsius temperature to isolate the deeper traps. We have proposed and realized three methods for simultaneous determination of trap depth and decay parameter based on the quasi-equilibrium model and experimental data. If we treat the case of kinetic order a = 1 as a = 2, the error might be as large as 100%.
文摘The acceleration ability of electrons in SiO2 and ZnS was compared through the variation of emission intensity based on ZnS : Er electroluminescence during the reverse of polarity of sinusoidal voltage. In order to avoid the influence of work function of electrode, cathodal and anodal materials were ITO (indium tin oxide). The ratio of maximum emission intensity under positive and negative half period is 2.18. This result demonstrates that the electron acceleration ability of SiO2 is 2.18 times stronger than that of ZnS.
基金supported by the National Natural Science Foundation of China (10774012 and 10434030)Beijing Jiaotong University Program (2007XM048, 2006XM038)
文摘Nanosized long-persistent phosphors SrS:Eu^2+, Dy^3+ were prepared by the hydrothermal method.The samples were characterized by X-ray powder diffraction, transmission electron microscopy, and charge-coupled device spectrometry.The persistence characteristic was studied using the decay curves.The results showed that the emission intensity decreased sharply with temperature increasing, although the particle size increased.The S2-vacancies caused by oxidization served as shallow traps, and Dy3+ served as deep traps in SrS:Eu^2+, Dy^3+.The afterglow intensity of SrS:Eu^2+, Dy^3+ was higher than that of SrS:Eu2+ prepared at the same temperature.However, the minimization span of initial afterglow with temperature for the former sample was larger than that for the latter.Binary-doped phosphor decayed more slowly than the singly doped one.The afterglow of SrS:Eu^2+, Dy^3+ decayed more quickly with the increase of sintering temperature.
基金Project(2003CB214501) supported by the National Basic Research Program of China Project(48010) supported by the Excellent Doctor’s Science and Technology Innovation Foundation of Beijing Jiaotong University, China
文摘Sputtering method was used to prepare Ni-Mo alloy electrodes for hydrogen production in alkaline solution. The influences of the working pressure during deposition and the substrate temperature on the electrochemical behavior of electrode were characterized by steady-state polarization plot and Tafel polarization curve measurements. And the physical properties of electrodes were characterized by XRD, SEM, AFM and EDS. It is found that the overpotential is significantly influenced by the working pressure which affects critically the electrode surface morphology, and two Tafel regions are observed for each sample. The overpotential value does not change very much with the substrate temperature. The XRD results indicates that the electrodes should be considered nanocrystalline. Thornton model for the microstructure of sputter-deposited electrodes is referred to explain the observed microstructure change.
基金Project supported bythe National Natural Science Foundation of China (60576016 ,10374001) Natural Science Foundationof Beijing (2073030) +1 种基金"973"National Key Basic Research Foundation of China (2003CB314707) National Natural Sci-ence Foundation of China (10434030)
文摘A novel rare earth complex Eu(TTA)2(N-HPA)Phen (TTA = thenoyltrifluoroacetone, N-HPA = N-phenylanthranilic acid, and phen = 1,10-phenathroline ), which contains three different ligands, was synthesized. The Eu complex was blended with poly N-vinylcarbazole (PVK) in different weight ratios and spin coated into films. The luminescence properties of films were investigated and energy transfer between PVK and the complex was discussed. Multilayer structural devices consisting of ITO/PVK: Eu (TTA)2 (N-HPA) phen/BCP/Alq3/Al were fabricated with PVK : Eu (TTA)2(N-HPA) as light-emitting layer. Increasing the concentration of Eu in the PVK thin film would inhibit the emission of PVK to different degrees. Finally, the pure red luminescence of europium( Ⅲ ) was observed when the doping weight ratio was approximately 1 : 5, which indicated an effective energy transfer from PVK to rare earth complex.
基金supported by the National Basic Research Program of China(Grant Nos.2011CB932700 and 2011CB932703)the National Natural Science Foundation of China(Grant Nos.61335006,61378073,and 61077044)+1 种基金the Beijing Natural Science Foundation,China(Grant No.4132031)the Fundamental Research Funds for the Central Universities of Beijing Jiaotong University,China(Grant No.2014YJS136)
文摘In order to investigate the impedance matching properties of microwave absorbers,the ternary nanocomposites of GO/PANI/Fe3O4(GPF) are prepared via a two-step method,GO/PANI composites are synthesized by dilute polymerization in the presence of aniline monomer and GO,and GO/PANI/Fe3O4 is prepared via a co-precipitation method.The obtained nanocomposites are characterized by scanning electron microscopy(SEM),X-ray diffraction(XRD),and Fourier transform infrared spectroscopy(FTIR),respectively.The microwave absorbability reveals enhanced microwave absorption properties compared with GO,PANI,and GO/PANI.The maximum reflection loss of GO/PANI/Fe3O4 is up to-27 dB at 14 GHz with its thickness being 2 mm,and its absorption bandwidths exceeding-10 dB are more than 11.2 GHz with its thickness values being in the range from 1.5 mm-4 mm.It provides that GO/PANI/Fe3O4 can be used as an attractive candidate for microwave absorbers.
基金Supported by the National Natural Science Foundation of China under Grant No 50972007the Beijing Municipal Natural Science Foundation under Grant No 4092035+2 种基金the National Basic Research Program of China under Grant No 2011CB932703the National Science Fund for Distinguished Young Scholars under Grant No 60825407the Special Items Fund of the Beijing Municipal Commission of Education,and the Opened Fund of the State Key Laboratory on Integrated Optoelectronics.
文摘We report on the fabrication and electrical characteristics of Ga-doped ZnO thin film transistors(TFTs).Low Ga-doped(0.7wt%)ZnO thin films were deposited on SiO_(2)/p−Si substrates by rf magnetron sputtering.The GZO TFTs show a mobility of 1.76 cm2/V⋅s,an on/off ratio of 1.0×10^(6),and a threshold voltage of 35 V.The time−dependent instability of the TFT is studied.The VTH shifts negatively.In addition,the device shows a decrease of the on/off ratio,mainly due to the increase of the off-current.The mechanisms of instability are discussed.
基金the financial supporting from the NSFC(61975006,61675017)NSFRPSI(Y72Z090Q10)+3 种基金the NSFCQ(cstc2019jcyj-msxm X0400)the NYTPP(R52A199Z11)the YIPACAS(E0296104)the BNSF(4192049)。
文摘Small molecule organic photovoltaics(SMPVs) were prepared by utilizing liquid crystalline donor material BTR-Cl and two similar optical bandgap non-fullerene acceptor materials BTP-BO-4 F and Y6.The BTPBO-4 F and Y6 have the similar optical bandgap and different absorption coefficients.The corresponding binary SMPVs exhibit different short circuit current density(/sc)(20.38 vs.23.24 mA cm^(-2)),and fill factor(FF)(70.77% vs.67.21%).A 14.46% power conversion efficiency(PCE) is acquired in ternary SMPVs with 30 wt% Y6,companied with a JSC of 24.17 mA cm^(-2) a FF of 68.78% and an open circuit voltage(Voc) of 0.87 V.The improvement on PCE of ternary SMPVs should originate from the well trade-off between phase separation and photon harvesting of ternary active layers by incorporating 30 wt% Y6 in acceptors.This work may deliver insight onto the improved performance of SMPVs by superposing the superiorities of binary SMPVs with similar optical bandgap acceptors into one ternary cell.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 60978060, 10804006, and 10974013)the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20090009110027)+4 种基金the Research Fund for the Youth Scholars of the Doctoral Program of Higher Education, China (Grant No. 20070004031)the Beijing Municipal Natural Science Foundation of China (Grant No. 1102028)the Beijing Municipal Science & Technology Commission of China (Grant No. Z090803044009001)the National Basic Research Program of China (Grant No. 2010CB327705)the International Science and Technology Cooperation Program (Grant No. 2008DFA61420)
文摘In this work, bathocuproine (BCP) and bathophenanthroline (Bphen), commonly used in small-molecule organic solar cells (OSCs), are adopted as the buffer layers to improve the performance of the polymer solar cells (PSCs) based on poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV): [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) bulk heterojunction. By inserting BCP or Bphen between the active layer and the top cathode, all the performance parameters are dramatically improved. The power conversion efficiency is increased by about 70% and 120% with 5-am BCP and 12-nm Bphen layers, respectively, when compared with that of the devices without any buffer layer. The performance enhancement is attributed to BCP or Bphen (i) increasing the optical field, and hence the absorption in the active layer, (ii) effectively blocking the excitons generated in MEH-PPV from quenching at organic/aluminum (Al) interface due to the large band-gap of BCP or Bphen, which results in a significant reduction in series resistance (Rs), and (iii) preventing damage to the active layer during the metal deposition. Compared with the traditional device using LiF as the buffer layer, the BCP-based devices show a comparable efficiency, while the Bphen-based devices show a much larger efficiency. This is due to the higher electron mobility in Bphen than that in BCP, which facilitates the electron transport and extraction through the buffer layer to the cathode.
基金supported by the Fundamental Research Funds for the Central Universities(No.2019RC020)
文摘In the past five years,all-inorganic metal halide perovskite(CsPbX3,X=Cl,Br,I)nanocrystals have been intensely studied due to their outstanding optical properties and facile synthesis,which endow them with potential optoelectronic applications.In order to optimize their physical and chemical properties,different strategies have been developed to realize the controllable synthesis of CsPbX3 nanocrystals.In this short review,we firstly present a comprehensive and detailed summary of existed synthesis strategies of CsPbX3 nanocrystals and their analogues.Then,we introduce the regulations of several reaction parameters and their effects on the morphologies of CsPbX3 nanocrystals.At the same time,we provide stability improvement methods and representative applications.Finally,we propose the current challenges and future perspectives of the promising materials.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10974013, 60978060, and 10804006)the Research Fund for the Doctoral Program of Higher Education, China (Grant No. 20090009110027)+5 种基金the Beijing Municipal Natural Science Foundation, China (Grant No. 1102028)the National Basic Research Program of China (Grant No. 2010CB327704)the National Natural Science Foundation for Distinguished Young Scholars (Grant No. 60825407)the Beijing Municipal Science and Technology Commission, China (Grant No. Z090803044009001)the Science Fund of the Key Laboratory of Luminescence and Optical Information, Beijing Jiaotong University, Ministry of Education, China (Grant No. 2010LOI12)the Excellent Doctor's Science and Technology Innovation Foundation of Beijing Jiaotong University, China (Grant No. 2011YJS073)
文摘A yellow phosphor, Ca2BO3CI:Eu2+, is prepared by the high-temperature solid-state method. Under the condition of excitation sources ranging from ultraviolet to visible light, efficient yellow emission can be observed. The emission spectrum shows an asymmetrical single intensive band centred at 573 nm, which corresponds to the 4f65dl→4f7 transition of Eu2+. Eu2+ ions occupy two types of Ca2+ sites in the Ca2BO3C1 lattice and form two corresponding emission centres, respectively, which lead to the asymmetrical emission of Eu2+ in Ca2BO3C1. The emission intensity of Eu2+ in Ca2BO3C1 is influenced by the Eu2+ doping concentration. Concentration quenching is discovered, and its mechanism is verified to be a dipole-dipole interaction. The value of the critical transfer distance is calculated to be 2.166 nm, which is in good agreement with the 2.120 nm value derived from the experimental data.
基金This work is supported by National Natural Science Foundationof China(20344002,10434030) State Key Program forBasic research of China (2003CB314707)
文摘In this paper a preliminary investigation of a novel optoelectronic polymer, poly (p-phenylene N-4-n-butylphenyl-N,N-bis- 4-vinylenephenylamine) (PNB), is reported. A single layer structure of ITO/PNB/Al was prepared via spin-coating of PNB solution as a thin film on the top of an ITO substrate, while aluminum top electrode was vacuum evaporated. Dark current- voltage characteristics of this device showed a typical rectifying behaviour. Photovoltaic response under a monochromatic illumination at 420 nm was observed, with an open circuit voltage of 0.3 V and fill factor of 0.21. Spectral response and optical absorption were found to be matched well. It was also discovered that the device showed a green electroluminescent emission at a forward bias. Turn-on voltage of the device was about 6 V and light output about 22.6 nW at a forward bias of 10 V. The work demonstrated that the PNB material might possess dual exciton sites resulting in a competition for excitons to be either separated or recombined. Both effects were associated with each other, which limited the photovoltaic or electroluminescence to some degrees.
基金Supported by the National Natural Science Foundation of China under Grant Nos 60577020 and 60672004.
文摘We introduce a generalized concept of principal state of polarization (PSP) to analyse the piezoelectric polarization controller (PPC) and find each PPC unit can be described by a rotation matrix determined by the PSP. Our PPC has three components, each made of a jaw and a piezoelectric actuator with the squeezing direction tilted 0°, 45° and 0°, which are driven by a tunable power supply. We demonstrate that all the polarization rotation angles are linear to driving voltages and the PSP of unit 2 is nearly orthogonal to others which are almost equal. Taking some approximate treatments we obtain the matrix model of our PPC with respect to three driving voltages. The average error of our theoretical model is 1.51°, and the polarization response time is 〈50 μs, which is promising to realize an open-loop control of polarization.
基金supported by the National Natural Science Foundation of China(Grant No.61377028)the Natural Science Funds for Distinguished Young Scholar,China(Grant No.61125505)the Fundamental Research Funds for the Central Universities,China(Grant No.2014JBZ009)
文摘N-dodecanethiol capped zinc sulfide(Zn S) nanocrystals were synthesized by the one-pot approach and blended with poly(N-vinylcarbazole)(PVK) to fabricate electrical bistable devices. The corresponding devices did exhibit electrical bistability and negative differential resistance(NDR) effects. A large ON/OFF current ratio of 104 at negative voltages was obtained by applying different amplitudes of sweeping voltage. The observed conductance switching and the negative differential resistance are attributed to the electric-field-induced charge transfer between the nanocrystals and the polymer,and the charge trapping/detrapping in the nanocrystals.