Biomedical subjects

Feng Teng

Publications and source records attributed to Feng Teng.

18 recordsLinked to original sources

PubMed2006

[The emission of organic-inorganic single quantum well with organic heterojunction].

Organic-inorganic single quantum well with organic heterojunction ITO\SiO2 (60 nm)\MEH-PPV(40 nm)\Alq3 (40 nm)\SiO2 (60 nm)\Al has been fabricated. With the detailed investigation of photoluminescence and electroluminescence of this novel device, the authors found that the permittivity confinement effect and the quantum size effect have obviously an effect on the optical and electrical properties of organic-inorganic quantum well with organic heterojunction. The electroluminescence of organic-inorganic quantum well with organic heterojunction included three different emissions under alternative-current voltages: 410, 510 and 590 nm, which originated from radiative recombination of MEH-PPV, recombination of Alq3 excitons and MEH-PPV excitons respectively.

English Abstract↗

PubMed2006

[Spectral properties of energy transfer in doubly doped polymer electroluminescence].

The authors report a cascade energy transfer based on the long-range dipole-dipole Förster energy transfer between polymer and two fluorescent dyes in solid thin films. The authors studied the fabrication and emission characteristics of a new doubly doped system for color purity and energy transfer efficiency, in which two fluorescent dyes, i. e. TPB and Rubrene were doped into PVK. In the blend film, PVK acted as the energy donor, Rubrene as the fluorescent dye, and the assistant dopant TPB was used to facilitate the energy transfer from PVK to the dye Rubrene. Orange emission comes from Rubrene via a cascade energy transfer from PVK toTPB and then from TPB to Rubrene.

English Abstract↗

PubMed2006

[Study of color-changing device controlled by frequency and its mechanism].

Absorption is the underlying reason for the change in luminescence traits. And the lifetime influences the absorption in turn. This is a common law not only suitable for photoluminescence but also for other types of luminescence. In field emission display, two kinds of luminescence center have dramatically dissimilar lifetimes, which are co-doped in the same material. The spectrum changes with excitation frequency. Tuning color comes into reality in the same materials. The experiment proves that this law has something to do with lifetime, but has nothing to do with the way of excitation and the reasons for abruptly quenching.

English Abstract↗

PubMed2006

[The influence of holes buffer layer doped with different one-dimensional nanomaterials on the performance of polymer light-emitting diodes].

The effect of holes buffer layer PEDOT doped with one-dimensional nanomaterials on the performance of polymer light-emitting diodes was investigated. The photoluminescence efficiency of double layer sample PEDOT/MEH-PPV was enhanced by doping one-dimensional nanomaterials (TiO2 nanotube and ZnO nanorod) into PEDOT layer. Stronger interaction of one-dimensional nanomaterials and PEDOT suppressed the creation of defect states which can quench radiative recombination of excitons. The electroluminescence efficiency of device was improved by 2 and 2.5 folds by doping TiO2 nanotubes and ZnO nanorods into holes buffer layer PEDOT respectively.

English Abstract↗

PubMed2006

[Optical and morphological investigation on the interaction of dual dopants in poly (N-vinylcarzole)].

The effect of optical and electrical properties of poly(N-vinylcarzole) (PVK) doped with two dyes, i. e. 8-tris-hydroxyquinoline (Alq3) and 4-(dicyanomethylene)-2-tert-butyl-6 (1, 1, 7, 7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB), on the energy transfer and charge trapping processes was investigated. The phase separation in blends film at different doping concentration was also studied. More homogeneous dispersion of dyes in PVK with increasing doping concentration was showed. The results indicate that there is a certain interaction of Alq3 and DCJTB in this dual-doped system. It is the incorporation of DCJTB that untangled the aggregation of Alq3 owing to the interaction of DCJTB and Alq3. But for higher doping concentration, DCJTB results in an isolated charge transport channel that decreases the electroluminescence (EL) operating voltage.

English Abstract↗

PubMed2006

[The influence of frequency on solid state cathodoluminescence].

Solid state cathodoluminescence (SSCL) is a new mechanism of light emission in organic-inorganic system. In the present article, we get SSCL under sinusoidal alternating-current voltage with a structure of ITO/SiO2/MEH-PPV/SiO2/Al. The spectra have two peaks: 410 and 580 nm, which obey molecular theory and band model, respectively. The temporal behaviors of both peaks in SSCL are studied with a new method of estimating lifetime in frequency domain. The intensity of the peak at 410 nm decreases as the frequency of the driving voltage increases, and the intensity of the peak at 580 nm increases as the frequency of the driving voltage increases. The difference in the dependence of light intensity on the frequency of excitation comes from the difference in the lifetime of the two peaks. The lifetime of short wavelength emission is found to be less than 5 ms while that of long wavelength emission is more than 0.05 ms.

English Abstract↗

PubMed2005

[Investigations on the movement of pigment particles in the electrophoretic liquids].

In the present report, the authors studied the movement of pigment particles which decide the display status, enduced the equation of the motion and the expression of reflectivity, and estimated the value of the delay time. Combining the above theoretical conclusion with the experimental results, the authors discussed the feasibility of the passive matrix addressing of electrophoretic image displays, and provided good advice on how to acquire display devices of good quality.

Algorithms↗

PubMed2005

[Study of water-sol core-shell CdSe/CdS quantum dots].

Water-sol core/shell CdSe/CdS quantum dots (QDs) were synthesized in aqueous solution by using mercapto-acetate acid as stabilizer. The UV-Vis absorption and emission spectra were studied. The size of the SdSe-core was about 2 nm estimated by absorption edge and X-ray powder diffraction(XRD). The structure was also characterized by X-ray photoelectron spectroscopy(XPS). The intensity of luminescence of the quantum dots was greatly enhanced after the surface was modified with CdS shell. Red shift of the peak was shown in both the emission and absorption spectra.

Algorithms↗

PubMed2005

[The study of electroplex emission based on PVK/BCP].

Electroplex emission based on poly(N-vinylcarbazole) (PVK) and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) has been studied. A emission peak at 595 nm was observed in EL spectrum but not in PL spectra in the devices. The emission originates from the transition between the excited state of BCP and the ground state of PVK. Because of the increase of emission zone, the device of PVK: BCP blend exhibited stronger electroplex emission. The emission of electronplex was enhanced for both of PVK/BCP double layer device and PVK:BCP blend device, and it is stronger for blend devices. At higher drive voltage, only electroplex emission was observed in the blend device.

Algorithms↗

PubMed2005

[Study of PVK: TPB thin film by using stable spectra].

The energy transfer between PVK and TPB in PVK:TPB thin film in different concentrations was studied by emission spectra, excitation spectra, and absorption spectra. It is proved that the energy can be transfered from PVK to TPB in a wide concentration range and the transfer is most efficient at the concentration of 5% wt. A model Hamitonian based on a single chain model including the dopant was proposed to simulate the experiment. This model can be used to explain the experimental results very well.

English Abstract↗

PubMed2005

[Upconversion luminescence properties of YLiF4:Er, Tm, Yb synthesized by hydrothermal method].

YLiF4 codoped with Er3+, Tm3+ and Yb3+ ions was synthesized by hydrothermal method. The absorption spectra and upconversion spectra excited at 980 nm were investigated. Under the excitation of infrared photons, strong white emission can be obtained. According to the value of n obtained from the power law, the 484 nm blue emission, 524 and 552 nm green emission, and 665 nm red emission are all due to two photon process, while the UV emission is attributed to three photon process. The authors also analyzed the upconversion mechanism and process.

English Abstract↗

PubMed2005

[Studies on photoluminescence spectra of polyfluorene under modulation of electric field].

The photoluminescence of polyfluorene thin film modulated by an electric field are studied. The results show that the photoluminescence from polyfluorene film can obviously quenched by the extra electric field, which is attributed to the electric field-induced dissociation of photogeneration excitons. The dependence of the exciton dissociation rate constant on the intensity of electric filed is fitted. The average hopping distance of element charge is 0.68 nm in PFO. This volume is comparable with the reported results in Alq3 and polymers. The spectral dependence of the factor of EFIQP is given. The dissociation of hot-exciton is deduced, which influences on the spectral dependence of the EFIQP factor slightly.

Algorithms↗

PubMed2005

[Simultaneous determination of rate ratio of recombination to capture and trap depth from thermo-luminescence of ZnS:Cu, Co].

The recombination luminescence is in nature a bimolecular process but, the decay rule may be changing from that of mono-molecular to bimolecular rule, i.e., from exponential to hyperbolic rule, depending on the behavior of conduction electrons. This behavior is represented by relative rate of recombination with ionized centers to that of capture by traps. This relative rate depends partly on the intrinsic parameters of the specified materials, and partly on the concentration of conduction electrons supplied by traps. Each point of the TL curve is related to the material parameters and the release of electrons from traps. The ratio of relative rate of recombination to that of capture gamma(epsilon) = sigma0(n0)/sigma(nu - n) involves the parameter epsilon. They are inseparable and must be determined at the same time. In the present report, starting from the same sample ZnS:Cu, Co which has only one peak in its TL(i. e., only one kind of luminescent center and only one kind of traps), and the experimental value of sigma/sigma0 = 0.005, the authors use thermo-luminescence kinetics models and some mathematic tools to exactly estimate the ratio sigma0(n0)/sigma(nu) and the trap depth epsilon simultaneously from the glow curve. The authors found that sigma0(n0)/sigma(nu) = -2.6 and epsilon = 0.86 eV.

Cobalt↗

PubMed2005

[Proof of solid state cathodoluminescence by using brightness waveform].

Three different inorganic-organic hetero-junctions (A: ITO/SiO2/Alq3/Al, B: ITO/Alq3/SiO2/Al and C: ITO/SiO2/Alq3/SiO2/Al) were fabricated. The emission can be observed only under positive bias in devices A and B, but under both biases in device C according to their brightness waveforms. With increasing voltage, the increase in blue emission in devices B and C is faster than that in green emission. This is because that the recombination of hot electrons and holes, i.e., electron-hole pairs, produced blue emission in devices B and C, and the recombination of electrons injected from Al with the accumulated holes, which are excited by hot electrons, produced green emission in device A. Hence, the emissions of the devices are attributed to not only the recombination of electrons and accumulated holes, but also the cathodoluminescence-like (CL-like) emission.

English Abstract↗

PubMed2004

[Electroluminescence property of MEH-PPV/ZnO nano-crystal structure].

A new structure with II-VI nano-crystal ZnO film as the electron transport layer and MEH-PPV as the hole transport layer and emitting layer was fabricated. The new structure's brightness and efficiency were improved markedly compared with that of the single MEH-PPV layer structure. And a new peak at 620 nm was found in the ITO/MEH-PPV/ZnO/Al structure's electroluminescence spectrum, which should resulted from ZnO layer. In addition, the turning-on voltage of the two-layer structure decreased from 9 V of the single layer structure to 4 V. From the I-V curve, the authors concluded that the emitting area was around the interface of MEH-PPV/ZnO and the combination area could shift with changing the voltage.

English Abstract↗

PubMed2004

[The influence of thickness of SiO2 on the electron acceleration in cathodluminescence-like emission].

The authors investigated the property of cathodluminescence-like (CL-like) emission in the device of MEH-PPV sandwiched between two SiO2 layers. The authors observed in addition to the inherent electroluminescence of MEH-PPV, a shorter emission peak which is considered to be corresponding to HOMO-LUMO transition. From the relative change of these two peaks with the variation of the thickness of SiO2, The authors studied the electron acceleration ability of SiO2.

English Abstract↗

PubMed2004

[Photoexcitation mechanism of photoconductive device by organic/inorganic thin-film heteropairing].

Photoconductive devices with organic (polyvinylcarbazole-PVK)/inorganic (zinc-sulfide--ZnS) thin-film heteropairing were fabricated. In external field, the excitation profile of the steady-state photoconductivity and the primary photoexcitation process of hybrid devices were presented and discussed. Comparison of photoconductivity of the devices and absorption spectra of PVK and ZnS implied that both layers absorption contributes to the photocurrent, but the effective part is at the interface of PVK and ZnS. The dependence of maximum photocurrent on the applied voltage and the dark and illuminated current spectra indicates the ultrafast charge transfer at the interface.

Electrochemistry↗

PubMed2004

[Luminescence properties of a new kind of rare earth complexes Tb(m-benzoicacid)3].

The luminescence properties of a new kind of rare earth complex Tb(m-benzoicacid)3 were studied. With the new complex as the dopant and PVK as the host, the film of the mixed system was made, from whose spectra the authors learned that a highly efficient energy transfer process exists. The energy transfer is related to the mass proportion, and the more the mass proportion of Tb in the doped system, the more the emission proportion, and at the same time the emission of PVK is relatively weak. When the mass proportion of Tb(m-benzoicacid)3:PVK is higher than 20%, the emission of Tb is stronger than that of PVK, and plays the main role, while the emission of PVK disappears. The authors used the PVK:Tb(m-benzoicacid)3 system as the emission layer and Alq as the electron-transfer layer, thus the device, whose structure is ITO/PVK:Tb(m-benzoicacid)3/Alq/LiF/Al was formed. From the spectrum of this device, the characteristic emission of Tb can be observed. At the bias voltage of 21 V, a brightness 311 cd x m(-2) was achieved.

English Abstract↗