Papers by Keyword: Energy Level

Abstract: This work investigated green fluorescence Organic Light Emitting Diode (OLED) with four hole blocking materials HBMs. Aims to enhance color performance in QD-OLED panels to produces a set of light with red, green, and blue sub-pixels. The HBM examined in this scenario consist of: (4,7-diphenyl-1,10-phenanthroline)Bphen, Tris(8-hydroxyquinoline aluminium)Alq₃, (2,2′,2″-(1, 3,5-benzinetriyl)-tris(1-phényl-1-H-benzimidazole)TPBi, (3-phényl-4(10-naphtyl)-5-phényl-1,2,4-triazole)TAZ. These holes blockings materials have different electron mobility and different hole-blocking barriers. A numerical model based on the drift-diffusion formalism was created to study electron and hole transport in OLEDs. The model includes continuity equations, conduction diffusion current, and the Poisson equation. The simulation showed the performance of each device was affected by these properties of each HBM. The width of the emission zone depends on the HBMs employed, and when the electron mobility increases the recombination zone is wide in the HBL. It was found that the device with Bphen, Alq3, TPBi, and TAZ have electrical and optical characteristics that are respectively: Langevin recombination rate (2.25 x10²⁵ cm^-3s^-1, 1.74 x10²⁵ cm^-3s^-1, 1.04x10²⁵ cm^-3s^-1,1.79x10²⁴ cm^-3s^-1), singlet exciton density (2.87x10¹⁴ cm^-3, 2.2x10¹⁴ cm^-3, 1.31x10¹⁴ cm^-3, 0.22x10¹⁴ cm^-3), luminance (4700 cd/m², 4500 cd/m², 4400 cd/m², 3200 cd/m²). Our study provides a model system to examine the role of hole blocking materials on OLED optoelectronic properties.

Abstract: The energy level structure and spectral characteristics of Yb-doped fiber laser are analyzed,and the absorption and emission cross sections of ytterbium ions in quartz matrix are given. It can beseen that there are two absorption peaks, 915 nm and 975 nm, respectively. The absorption coefficientcorresponding to 915 nm absorption peak is smaller, but the absorption spectrum is wider. Theabsorption coefficient corresponding to the absorption peak at 975 nm is relatively large, but thespectrum width is very narrow. The advantages and disadvantages of Yb3+ doped laser materialscompared with other rare earth ions doped laser materials are analyzed. It is pointed out that Yb3+itself, due to its strong absorption and emission at 980 nm, disperses the pump power in the innercladding of double cladding optical fibers and reduces the pump efficiency.

Abstract: Organic layers deposited on various polarity substrates and the electronic structures of (PTCDA/TiOPc) on hydrophobic and hydrophilic substrates have been studied by ultraviolet photoemission spectroscopy. The difference between work function and polarity of the substrates induce the formation of an interface dipole with corresponding shift in the relative position of molecular levels across the interface. While the vacuum level and open circuit voltage show vastly difference respectively, the barrier between anode-organic or organic-cathode also changes from 0.75eV to 1.13eV or 0.35eV to 0.65eV. The results show the possibility of tuning the electronic structure by the modification of substrate and potential applications on performance enhancement in organic electronic devices.

Abstract: In this research proposal we want to develop from kinematic data, measures using thewavelets theory to characterize normal and osteoarthritis knee locomotion. The kinematic data of theradio-carpal flexion-extension angles were analyzed using the wavelet transform. The experimentaldata was acquired with a complex goniometer system. The detail energy for the level 5 is an importantfactor to characterize the osteoarthritis patients and normal subjects.

Abstract: In order to enhance efficiency of laser engraving technology in fabric manufacture, a laser engraving experiment was conducted on 30 kinds of jeans with CO₂ laser engraving machine, and meanwhile the performance parameters of fabric was tested. Then five performance parameters of fabric were chosen through correlation analysis, with each showing a significant correlation with carving levels; a prediction model of carving level was constructed based on GRNN, with a prediction error of less than 3%.The study improves the efficiency of laser engraving and lays foundation for bridging the performance parameters of fabric and sculpture levels .

Abstract: Considering the crystal field parameter D_q and average covalent factor N, the energy levels of NaMg₃Al(MoO₄)₅: Cr³⁺ crystal at 295 K are calculated by diagonalizing the energy matrix of 3d³. At low temperature 9 K the bond length of Mg-O is calculated by adjusting the value to fit the spectra of Mg site. The value of Mg-O bond length is 2.0528 Å. The equation relationship of Mg-O between bond length and temperature is achieved.The calculated values are consistent with the experimental spectra.

Abstract: We have observed five electron traps with energy levels at 0.16, 0.30, 0.40, 0.53 and 0.67 eV below the conduction band in Pd and H doped Si by DLTS technique. Successive annealing at 373 K and 473 K for 30 min respectively caused two levels at Ec-0.16 eV and Ec-0.67 eV to disappear and simultaneously a new level to emerge at Ec-0.19 eV. From such annealing behavior and the comparison of the energy levels observed in the present study with those in the literature, we assign them to various Pd and H related defects as follows, Pd-H2: Ec-0.16 eV and Ec-0.67 eV, Pd acceptor: Ec-0.19 eV, Pd-H3: Ec-0.30 eV, Pd-H1: Ec-0.40 eV.

Abstract: We have recently shown that Sn impurity atoms are effective traps for vacancies (V) in Ge:Sn crystals irradiated with MeV electrons at room temperature [V.P. Markevich et al., J. Appl. Phys. 109 (2011) 083705]. A hole trap with 0.19 eV activation energy for hole emission to the valence band (E_h) has been assigned to an acceptor level of the Sn-V complex. In the present work electrically active defects introduced into Ge:Sn+P crystals by irradiation with 6 MeV electrons and subsequent isochronal annealing in the temperature range 50-300 °C have been studied by means of transient capacitance techniques and ab-initio density functional modeling. It is found that the Sn-V complex anneals out upon heat-treatments in the temperature range 50-100 °C. Its disappearance is accompanied by the formation of vacancy-phosphorus (VP) centers. The disappearance of the VP defect upon thermal annealing in irradiated Sn-doped Ge crystals is accompanied by the effective formation of a defect which gives rise to a hole trap with E_h = 0.21 eV and is more thermally stable than other secondary radiation-induced defects in Ge:P samples. This defect is identified as tin-vacancy-phosphorus (SnVP) complex. It is suggested that the effective interaction of the VP centers with tin atoms and high thermal stability of the SnVP complex can result in suppression of transient enhanced diffusion of phosphorus atoms in Ge.

Abstract: The energy problem of weak anchoring nematic liquid crystal (NLC) cell is investigated. For given system, there are four solutions satisfying mechanical equilibrium conditions simultaneity under certain condition. Liquid crystal system exist quanta energy level. The values and sequence of energy levels related to the change of external field and anchoring parameters. The state with the smallest energy is the stable state and the others are metastable states, which are separated by the energy barriers. The Freedericksz transition can be considered as the director slippage through these barriers to the lowest energy level and the first order transition and bistable state result from the existence of the multiple disturbed solutions.

Abstract: Defects induced in silicon crystals by irradiations with 6 MeV electrons in the temperature range 60 to 500 oC have been studied by means of deep level transient spectroscopy (DLTS) and high-resolution Laplace DLTS. Diodes for the study were fabricated on n-type epitaxially grown Si wafers. The DLTS spectra for the samples irradiated at elevated temperatures were compared with those for samples, which were subjected to irradiation at 60 oC and subsequent isochronal anneals in a furnace. The dominant radiation-induced defects in the samples irradiated at temperatures lower than 400 oC were found to be vacancy-oxygen (VO) and interstitial carbon – interstitial oxygen (CiOi) complexes. The introduction rates of the VO and CiOi centers increased about twice upon raising the irradiation temperature from 50 to 400 oC. It is argued that this effect is associated with either a) the suppression of the annihilation rate of Frenkel pairs or b) a decrease in the threshold energy for displacement of a host Si atom upon increase in the irradiation temperature. Transformations of deep level traps due to divacancies (V2) and trivacancies (V3) to V2-oxygen and V3-oxygen complexes were found to occur upon irradiation or annealing at temperatures exceeding 250 oC. A clear anti-correlation between changes in the minority carrier life time induced in the p+-n diodes by irradiation at different temperatures and changes in the concentrations of radiation-induced vacancy- and vacancy-oxygen-related complexes was found.