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Blue-purple emitting Sr_2-xSiO₄:xCe³⁺ (x=0.01-0.09, in steps of 0.01) and Sr_1.95-ySiO₄:0.05Ce³⁺, yLi⁺ (y=0.01-0.07, in steps of 0.02) phosphors have been prepared by co-precipitation method with MCM-41 as silica source. The emission spectra of Sr_2-xSiO₄:xCe³⁺ show an asymmetric broad band with a maximum around 410 nm and the critical mole fraction is found to be 5%. Ce³⁺ ions prefer nine-coordinated Sr(Ⅱ) sites over ten-coordinated Sr(Ⅰ) sites. The emission intensity of Sr_1.95SiO₄:0.05Ce³⁺ can be improved effectively by co-doping Li⁺ ions as charge compensator and a greater degree of the improvement is observed for phosphor calcined at 1 100 ℃ compared with 1 000 ℃. The most suitable doping amount of Li⁺ for Sr_1.95-ySiO₄:0.05Ce³⁺,yLi⁺ is y=0.05.

The red emitting phosphors M₂Eu_xLn_1-xAlO₅ (M=Ca, Sr, Ba, Ln=La, Lu, Gd) were synthesized through the solid state reaction technique. The photoluminescence properties were described. Upon excitation with UV and near UV light excitation, the photoluminescence emission spectra could be assigned to the transitions of Eu³⁺ from the initial state ⁵D₀ to the final states ⁷F_J (J=0,1,2,3,4). The two strong emissions peaked at 590 nm and 620 nm, which arose from the ⁵D₀-⁷F₁ and ⁵D₀-⁷F₂ transitions of Eu³⁺, respectively. The photoluminescence excitation spectra show abroad O^2--Eu³⁺ charge-transfer band and f-f transitions. O^2--Eu³⁺ charge-transfer bands of M₂Eu_xLa_1-xAlO₅ (M= Ca,Sr,Ba) shift to the longer wavelength in order of Ca, Sr, Ba. The replacement of Ln in Sr₂Eu_xLn_1-xAlO₅ by La, Gd and Lu was studied. The dependence of the integrated luminescence intensities on Eu³⁺ concentration was presented. The lifetimes of Sr₂Eu_xLa_1-x-AlO₅ and Sr₂Eu_xGd_1-xAlO₅ were analyzed.

On the basis of Lee-Low-Pines (LLP) unitary transformation, the eigenenergy and eigenfunction of the ground-state and the first excited state of the strong-coupling bipolaron in two-dimensional quantum dot (QD) were obtained by using the variational method of Pekar type. A qubit was formed by overlaying both the ground state and the first excited state of the bipolaron system. Numerical calculations indicate that the oscillating period T₀ of qubits decreases with the increasing the electron-phonon coupling strength α, the confinement strength ω₀ of the quantum dot, and the dielectric constant ratio η; the distribution of the probability density Q of the electrons in quantum dot oscillates periodically with time t, angle coordinate ø₂, and the dielectric constant ratio η, and there is a maximum at near the center and zero away from the center of quantum dot.

Na_0.5Bi_0.49Eu_0.01TiO₃ nanopowders were prepared by the hydrothermal method under different conditions. The synthesized nanopowders were characterized by X-ray diffraction, UV-visible spectra, transmission electron microscopy and photoluminescence spectra. The results reveal that the phase-pure rhombohedral perovskite structure NBT-Eu powders can be prepared at a hydrothermal temperature of 200 ℃ for 24 h with 12 mol·L^-1 NaOH and 0.6 mL OP-10. The powders exhibit nanorod shape with a diameter of 15 to 200 nm. Under the excitation of 458 nm light, NBT-Eu nanopowders exhibit the strongest emission at 689 nm, which can be attributed to ⁵D₀→⁷F₄ transition of Eu³⁺.

A new tailed-porphyrin H₂TPP-BzIm and different transition metalloporphyrins (Fe, Co, Zn) were synthesized and characterized by ¹H NMR, MS, IR, UV-Vis. The spectral and electrochemical properties were studied by UV-Vis spectrum, fluorescence spectrum and cyclic voltammetry method. Compared with tetraphenyporphyrin(H₂TPP), the absorption and emission peaks of the tailed porphyrin have obvious red-shifts. The CV curves of Fe, Co metalloporphyrins indicate that Fe and Co undergo the changing of oxidation state in addition to the redox on the porphyrin ring.

AgNbO₃/graphene nanocomposites were synthesized via the technique of solid-solid grinding and subsequent sintering process. Surface structures and optical properties of the prepared materials were characterized by transmission electron microscopy and UV-Vis diffuse reflection spectroscopy. The results indicate that band-gap of AgNbO₃ is lowered upon compositing with graphene nanoparticles, thereby giving an absorption in a large range of wavelengths. Degradation of methyl orange (MO) is carried out to evaluate the photocatalytic activity of AgNbO₃/graphene nanocomposites under visible light irradiation. Compared with pure AgNbO₃, AgNbO₃/graphene composites exhibit significantly enhanced photocatalytic activity for MO. Moreover, AgNbO₃/graphene (2:1) obtained at 300 ℃ exhibits the highest degradation degree of MO after an irradiation of 120 min with apparent k_app of 0.034 min^-1, which is about 10 times than that of the pure AgNbO₃. The tests of radical scavengers confirm that ·O₂^- and h⁺ are the main reactive species for the degradation of MO.

A set of organic light-emitting diodes were fabricated with a structure of ITO/ acid-treated PEDOT:PSS/NPB/Alq₃/LiF/Al. The optical and electrical properties were studied. It is found that OLED device with PEDOT:PSS films treated by 0.75 mol/L HCl(C₂H₂O₄) annealed at 120 ℃ for 15 min exhibits a better performance with a maximum luminous efficiency of 4.28 cd/A at 100 mA·cm^-2. The luminous efficiency of OLED with C₂H₂O₄-treated PEDOT: PSS is obviously increased by 34% than those no untreated.

MoO₃/Ag/MoO₃ (MAM) films were utilized for constructing bi-function electrochromic devices, which served as both transparent electrodes and electrochromic materials. MAM films were prepared by E-beam evaporation at room temperature. As a transparent electrode, MAM film has a good photoelectric performance with an average transmittance of 59.4% and a sheet resistance of 12.2 Ω/ □. As an electrochromic material, MAM film shows a fast response time (coloration time 4.3 s, bleaching time 11.1 s), a larger optical contrast of 25% at 528 nm, a good stability (100 cycles) and a higher coloration efficiency of 40.5 cm²·C^-1, which is at a high level among the reported data.

AlO_x thin films with various thicknesses were fabricated on p-type textured crystalline silicon wafers through atomic layer deposition. The optical and electrical properties of AlO_x thin films were significantly improved by adjusting their thicknesses. The reflectance of AlO_x thin films decreased from 10.12% to 0.96% with increasing thickness in a wide spectral range from 350 to 1 000 nm. The passivation effect of AlO_x was discussed by using quasi steady state photo conductance (QSSPC) and capacitance-voltage (C-V) measurement. The AlO_x thin film with the thickness of 32 nm shows the highest τ_eff and lowest interfacial state density (D_it). The origin of the polarity changing of the equivalent oxide charge (Q_f) for the annealed AlO_x thin film was also investigated.

According to the transition rates equation of Tm ion under stable condition, the analytical expression of time delay and the relative modulation attenuations was established. The time delay and fractional delay of slow light under different input power were calculated based on the numerical analysis. It is concluded that the larger time delay, the fractional delay and group refractive index can be obtained under high input power of signal. It is also observed that the peak position of the maximum fractional delay moves to high frequency.

The growth of GaN-based blue LED with different barriers temperature in multiple quantum wells on silicon substrate by MOCVD method was reported. The dependence of luminescence on barriers temperature was obtained. The relationship between external quantum efficiency (EQE) and barriers temperature under different current density showed that EQE increases with barriers temperature during the temperature from 860 to 915 ℃, and then EQE decreases a lot after the temperature over 915 ℃. The results of XRD, SIMS and EL support each other very obviously, which means that the luminescence efficiency is contributed on the sharpness of well-barrier interface. Over top temperature of barriers will result in a worse sharpness of well-barrier interface owing to an undesirable atoms diffusion. Much lower temperature of barriers will also cause a worse sharpness of well-barrier due to the non-step flow growth of barriers. The optimization barriers temperature range is from 895 to 915℃ for epitaxy growth.

InGaN-based LEDs with InGaN/AlInGaN and InGaN/GaN multiple quantum wells (MQWs) were theoretically studied and compared by using the Advanced Physical Models of Semiconductor Devices (APSYS) simulation program, respectively. The carrier concentrations in quantum wells, radiative recombination rate in active region, light-current performance curves, and the internal quantum efficiency were investigated. The simulation results show that higher efficiency realized in the strain-free AlInGaN barrier instead of GaN.

Ultraviolet organic light-emitting devices (UVOLEDs) were constructed by using hole-transport-emitting layer of 4,4'-bis(carbazol-9-yl)biphenyl (CBP) and electron-transport-emitting layer of 3-(4-biphenyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole (TAZ). The excimer forming zone was optimized by adjusting the functional layer thickness, which contriuted to device performance improvement. Our results indicate that the thickness variation of CBP has negligible effect on device performance while that of TAZ shows considerable effect. The maximum radiance of 4.4 mW/cm²@270 mA/cm² and external quantum efficiency (EQE) of 0.94%@12.5 mA/cm² are achieved in UVOLED with optimal thickness of 50 nm CBP and 30 nm TAZ. The electroluminescence peak of ~410 nm and shoulder of ~380 nm, resulted from CBP and TAZ, respectively, are observed. Moreover, an ultrathin layer of[CBP:TAZ] inserted between CBP and TAZ accelerates excimer recombination rate and reduces driving voltage. Meanwhile, the carrier balance is improved and thus device efficiency is slightly promoted (the maximum EQE reaches 0.97%@20 mA/cm²) without altering spectrum characteristics.

The effect of multilayer Ti/Al structure electrode on AlGaN/GaN HEMT Ohmic contact characteristics and the surface morphology were investigated. The specific contact resistance of all kinds of electrode structure was measured by transmission line model (TLM). The scanning electron microscope (SEM) was used to measure the electrode surface morphology. The experiment results show that the special contact resistance tend to decrease and the surface morphology tend to be smooth with the increasing of the number of Ti/Al layers in the same annealing conditions. The reducing of the thickness of Ti/Al layer can increase the specific contact resistance because of Au in-diffusion, but can slightly improve the surface morphology. High Ti ratio can reduce the formation of TiN, and lead to the increasing of specific contact resistance, but can greatly improve the surface morphology.

Based on excitation from a dual-wavelength CO₂ laser, the optical rectification (OR) in a multiple asymmetric quantum well (AQW) was theoretically investigated by using the compact density matrix approach and the iterative method. The numerical results for the typical Al_0.5Ga_0.5As/GaAs/Al_0.2Ga_0.8As material show that the dipole matrix element decreases with the increasing well width of the AQW. Moreover, the optical rectification coefficient depends sensitively on two pump light wavelengths and well width of the AQW. The physical origin of this shift in optical rectification curve is the quantum confinement effect in the AQW system which causes the separation of energy levels and the changes in resonant condition. For an AQW of 7 nm deep well-width and 23 nm shallow well-width, the maximum of optical rectification coefficient for the AQW is 5.925×10^-6 m/V when the two pump wavelengths are all 10.64 μm. The characteristics of optical rectification are also analyzed on parabolic and non-parabolic energy-band conditions in detail.

Water-soluble graphene quantum dots (GQDs) were synthesized by the pyrolysis of citric acid. Its fluorescent quantum yield was remarkly increased by PEG2000 modified. The luminescence characteristics of GQDs were studied by fluorescence spectroscopy, ultraviolet-visible spectroscopy, infrared spectroscopy as well as the fluorescence lifetime. A novel method for quantitative determination of trace carbazochrome (CBZC) was developed based on the fluorescence quenching of GQDs in pH 7.40 Tris-HCl buffer solution. A wide range of reaction parameters, such as concentration of GQDs, reaction time, surfactant, sorts and amount of buffer was examined. The screening results show that the ΔF was linearly related with the carbazochrome concentration from 4.0×10^-7 to 1.2×10^-5 mol/L(0.995 6) with the detection limit of 1.5×10^-7 mol/L. The relative standard deviation is 0.15% (n=5, c=4.0×10^-6 mol/L), when the concentration of GQDs is 2.3×10^-3 mol/L. The method has been used for the determination of carbazochrome in samples with the recoveries of 97.46%-101.6%. The interaction mechanism and main sorts of binding force between GQDs and carbazochrome were investigated by the temperature effect on the quenching constants and UV-visible absorption spectrometry.

We studied the transmission properties of a new grating structures composite of the matching heterostructure units containing lossy negative epsilon materials and photonic crystals by using finite element analysis. The transmittance was analyzed by comparing various grating period length and the different ratio of heterostructure in grating structures, respectively. The above results show that the transmittance of grating structures dramatically increases compare with the single heterostructure. Simultaneously, we expound the physical reason of the enhanced transmittance from the distribution of electromagnetic fields. That is because of the periodic modulation for electromagnetic fields in the new gating structures.

An indoor MIMO visible light communication system based on secondary reflection was proposed in this paper. Through model simulation, with the change of different spacing and different size of detectors on receiving surface at different position and different horizontal or vertical rotation of receiver, the receiving characteristics of indoor MIMO visible light communication were analyzed. The simulation results demonstrate that the changes of the detector spacing on receiving surface have little effect to the receiving optical signal, under the condition of signal can be recovered. SNR has different distribution when receiver is placed at different position. Moreover, the horizontal rotation of receiver has no effect on receiving optical signal, but the vertical rotation has a certain rotation range.

The change rule of circadian effects with ages in LED lighting of different color temperatures was studied. The ocular transmittances of different ages were introduced into the calculation formula of circadian action factor, and then the changes with ages and LED temperatures color were obtained. The heart rates of 12 old and 18 young male participates were measured in black and LED lighting of different color temperatures and the illuminance of 500 lx. The difference of heart rate between black and lighting was proposed to determine the circadian effect in order to verify the calculated results. Under the LED lighting conditions with the color temperatures of 6 500, 5 500, 4 500, 3 500 K, the circadian action factors of the young are 1.1, 0.7, 0.6, 0.44, respectively, and the heart rate changes differ significantly among different color temperature LED lighting. The circadian action factors of the old are 0.5, 0.3, 0.25, 0.2, respectively, and the heart rate change little among color temperatures. The circadian action factor of the same color temperature LED lighting decreases as the age increases. The circadian action factor of the young varies across different color temperatures LED lighting, therefore, the old changes little.