高场下界面势垒对双层有机器件复合发光的影响

以高场作用下载流子对三角势垒的Fowler-Nordheim隧穿理论为基础,建立了双层有机电致发光器件中载流子的输运和复合发光模型.计算并讨论了所加电压与界面势垒对器件的复合电流及其复合效率的影响.该理论模型很好地解释了实验现象,并进一步证实了电场对复合区域的调制作用. 关键词： 有机电致发光 双层器件 界面势垒     

输运层势垒对双层结构器件复合发光的影响

通过分析双层结构器件复合发光的实际物理过程，建立了双层器件载流子输运与复合发光的多势垒的理论模型，计算并讨论了器件复合效率随外加电压及输运层势垒（包括势垒高度和宽度）的变化关系，该理论模型较好地解释实验现象。     

高场作用下有机双层器件的场致复合发光

以在高场作用下载流子对三角势垒的Fowler Nordheim隧穿理论为基础 ,建立了双层有机电致发光器件载流子的输运与复合发光模型。求出了稳态下电荷载流子的复合发光与电压和界面势垒的函数关系式 ,计算并讨论了所加电压和阳极区与阴极区厚度之比 (Lh/Le)对复合发光的影响。该理论模型很好地解释了电场对复合区域的调制作用。     

界面空间电荷对双层有机电致发光器件效率的影响

本文建立了双层有机电致发光器件中载流子在有机/有机界面复合的无序跳跃理论模型.计算表明:①内界面处电子和空穴的有效势垒高义决定OLEDs中的电子和空穴密度的分布,而电子与空穴密度又决定了电场强度的大小;且复合效率随着有效势垒高度的增加而增加;②当电压较低时,复合效率随载流子有效跳跃距离的增加而增加;当电压较高时,复合效率随载流子的有效跳跃距离的增加而减少;③当界面场强差较小时,有机层界面场强突变增大,复合效率增大,当界面场强差达临界值时,复合效率反而随着界面场强差的增大而减小.该理论模型可较好地解释相关的实验现象.     

Characteristics of recombination in semiconductors with intercrystallite barriers

A model of nonuniform potential relief (modulated by adsorption of oxygen and an applied electric field) of a film containing centers of slow recombination distributed over the volume of a crystallite and centers of fast recombination localized on their boundaries is studied. The characteristic features of the current-voltage characteristics (CVC) of the photocurrent and the effect of adsorption of oxygen on the photoconductivity in semiconductors with intercrystallite barriers were studied. The saturation of the CVC is determined by the transformation of the surface trap levels into centers of fast recombination under the action of an electric field. The proposed model permits explaining from a unified viewpoint the sensitization and desensitization of a semiconductor as a result of oxygen chemisorption.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 56–60, March, 1989.     

Radiation of a tunneling electron on a secondary recombination center

Radiation emitted upon photorecombination of electrons produced in tunneling ionization on a nearly located center is considered. An analytic solution to one-dimensional and three-dimensional problems is obtained in the active-electron model. The dependence of radiation on the distance between the ionization and recombination centers and on the electric field direction is studied. Optimal parameters for producing recombination radiation are determined.     

圆筒内氢等离子体非定常化学反应羽流场DSMC分析

利用直接模拟Monte Carlo方法研究圆筒侧壁注入氢等离子体羽流场在8×10^-6s内的非定常流动特性.根据Bird的化学反应模型考虑离解-复合反应模型和电荷转移反应模型.在流场中注入H₂、H、金属原子X、H₂⁺和H⁺五种组分,研究离解-复合反应对流场中粒子分布和密度的影响,结果表明离解-复合反应使H₂数密度降低,H数密度增加,说明在流场中H₂的离解反应速率大于H的复合反应速率.加入电荷转移反应后H₂⁺数密度降低,H⁺数密度增加,对其他组分数密度没有显著影响.     

金属/有机界面势垒对单层有机电致发光器件发光效率的影响

基于高场下电荷的注入过程及激子的解离和复合过程,建立了单层有机发光器件电致发光(EL)效率的理论模型。计算表明：(1)当金属／有机界面势垒高度大于0．3eV时,器件的EL效率很低,降低金属／有机界面势垒可以显著提高器件的EL效率;(2)在较低偏压下,注入过程对器件的电致发光效率起主要作用,但在高偏压下复合过程起支配作用。这一模型可以阐明注入和复合过程对有机发光器件EL效率的影响,对选择发光材料、优化器件结构和提高器件EL效率具有指导意义。     

有机电致发光器件中载流子的输运和复合发光

以高场作用下载流子对三角势垒的FowlerNordheim隧穿理论为基础,建立了单层有机电致发光器件中载流子输运和复合发光模型,给出了薄膜中电子空穴对的解离和复合概率及电子和空穴的密度分布.计算并讨论了外加电压和注入势垒对器件电流和复合效率的影响. 关键词： 电致发光器件 载流子输运 载流子复合     

Kinetics of indirect electron-hole recombination in a wide single quantum well in a strong electric field

The kinetics of the indirect recombination of electrons and holes in wide single quantum wells in a strong electric field has been analyzed. It has been shown that the recombination time increases exponentially up to 20 μs due to the spatial separation of oppositely charged particles. The results of a theoretical model predicting the behavior of the recombination time as a function of the applied field are in good agreement with experimental data.     

Radiative recombination enhancement of bare ions in storage rings with electron cooling

Experiments on ion-electron recombination in electron coolers show an enhancement of the recombination rate with respect to the standard theory. The theoretical explanation of this effect is an active field of research. Here a parameter-free model is presented in terms of the Vlasov equation. Its inherent scaling rests on two dimensionless variables and agrees with measurements. Additionally, numerical calculations yield the correct magnitude for the enhancement and trace its cause to the process of beam merging.     

电场对单层有机电致发光二极管复合发光的影响

以电流连续性方程为基础，用易测量的注入电流密度来确定载流子浓度的边界值，得出载流子浓度和电流密度的解析表达式。计算并讨论了电子密度和电子电流密度在器件中的分布，电场对它们的影响以及电场与势垒对复合效率的影响。该模型较好地解释了有关实验现象。     

非等温模型下LED芯片性能与衬底的关系

发光二极管(LED)中载流子的输运及复合决定了其非均匀的内热源强度及分布,而芯片温度又影响载流子的输运及复合,两者具有强烈的耦合关系。本文利用非等温多物理场耦合模型对以蓝宝石、Si及SiC为衬底的 LED芯片的内量子效率、光谱特性及光电转换效率进行了系统研究。结果表明:以SiC为衬底的LED芯片具有最小的效率下垂效应(Efficiency droop)及最高的光谱强度和光电转换效率。这是因为与其他两种衬底的LED芯片相比,以SiC为衬底的LED芯片具有最好的散热性能,因此非均匀温度场对其载流子输运及复合的影响最小,使得活性区中的载流子浓度显著增强,漏电流明显下降。     

Modeling magnetic field effects in multispin systems

A model is proposed for calculating magnetic field effects formed in a radical triad composed of a biradical and a paramagnetic particle. To describe the influence of the “third” spin on the spin evolution in a biradical, the electron spin exchange interaction of the added spin with one of the paramagnetic centers of the biradical has been considered. Calculating the field dependence of the recombination probability of the biradical-oxygen complex revealed both an increase in recombination probability earlier attributed to spin catalysis and the influence of the values and signs of the exchange interaction in the complex on the shape of the magnetic-field effect dependence. Calculation results are in agreement with the experimental data on the photolysis of 7,7’-dimethyl-silanorbornadiene in aerated and deaerated solution.     

Study of the static characteristic I-V and the electrical parameters corresponding to the shunt resistance Rsh and series resistance Rs per unit area of a solar cell with grain size

This paper presents a new technique based on the junction recombination velocity (Sf: junction recombination velocity) at the grain size for the evaluation of the series and shunt resistances. The study of the response of the solar cell and the parameters of recombination in grain size, which are the object of the investigation, is related to the study of the static characteristic I-V and electrical parameters Rs and Rsh under a magnetic field. This study has allowed us to address some of the theoretical aspects of the field solar cell in order to draw a conclusion and some perspectives. Based on the results obtained for the photocurrent density and the photovoltage, we will study the I-V characteristic of the solar cell to then be able to propose a model for the determination of the shunt resistance Rsh and the series resistance Rs. Series resistance investigations, including numerical simulations and field data tests, are conducted to examine the energetic behavior of the PV modules for efficiency. Experimental results show that the proposed direct resistance-estimation method allows the PV modules to achieve their maximum power and efficiency under various operation conditions.     

Centrifugal electron-ion recombination

Transient electric-field pulses have been used to stimulate electron/ion recombination in a low density plasma in the presence of a static electric field. The measured recombination rates exhibit a strong dependence on the relative orientation of the pulsed and static fields. For weak pulses, the recombination rate is significantly higher for orthogonal as opposed to parallel or antiparallel field configurations. The enhanced recombination rate is attributed to the dynamic stabilization of high-m Rydberg levels that are populated during the pulse. Classical simulations confirm the importance of angular momentum rather than energy transfer.     

Hydrogen recombination in the early Universe in the presence of a magnetic field

Hydrogen recombination in the earlyUniverse in the presence of amagnetic field is studied. An equation for the recombination temperature in the presence of a magnetic field is obtained. The limiting cases of weak and strong magnetic fields are examined. A critical field above which the system being considered is in the atomic-hydrogen phase at any temperature is shown to exist. The relative shift of the recombination temperature in a magnetic field is estimated, and it is shown that this shift is small.     

Radiative life time of an exciton confined in a strained GaN/Ga1-xAlxN cylindrical dot: built-in electric field effects

The binding energy of an exciton in a wurtzite GaN/GaAlN strained cylindrical quantum dot is investigated theoretically.The strong built-in electric field due to the spontaneous and piezoelectric polarizations of a GaN/GaAlN quantum dot is included.Numerical calculations are performed using a variational procedure within the single band effective mass approximation.Valence-band anisotropy is included in our theoretical model by using different hole masses in different spatial directions.The exciton oscillator strength and the exciton lifetime for radiative recombination each as a function of dot radius have been computed.The result elucidates that the strong built-in electric field influences the oscillator strength and the recombination life time of the exciton.It is observed that the ground state exciton binding energy and the interband emission energy increase when the cylindrical quantum dot height or radius is decreased,and that the exciton binding energy,the oscillator strength and the radiative lifetime each as a function of structural parameters (height and radius) sensitively depend on the strong built-in electric field.The obtained results are useful for the design of some opto-photoelectronic devices.     

Gudden—Pohl effect and surface states in zinc sulphide phosphors

The classical electrophotoluminescent phenomenon, Gudden—Pohl effect (GPE), is used as a model to demonstrate the influence of surface states on the storage of optical excitation in A²B⁶ semiconductor compounds. Extensive experimental data on the investigation of GPE in ZnSCu phosphors are analysed and two possible approaches to interpretation of this phenomenon are discussed. From experimental data from the papers of Matossi and Riehl, some limitations in applying the model of Curie were determined. According to this model, the light flash of GPE must arise due to the increase of concentration of free electrons, released by the external electric field from electron traps. Also the model of GPE by Gol'dman is considered which relates the flash to recombination of free electrons and holes localized on the luminescence centres when the height of the collective repulsive barrier hindering recombination is decreased by the external field. This barrier is assumed to be created by the surface negative charge. A correlation between the GPE and the state of the persistent internal polarization in luminophors is discussed. This correlation makes it possible to use the light sum of the GPE flash as an optical indicator of the persistent internal polarization. An analogy is made between the GPE and the luminescent field effect for CdS single crystals due to the influence of the surface band bending on the luminescence intensity. The possibility of relating the GPE memory characteristics to the relaxation rate of the surface charge induced by the field is analysed.     

原子实对离子n壳层辐射复合截面的影响

基于Dirac-Slater相对论平均自洽场理论和类氢模型,研究了自由电子被辐射复合到裸核和类裸核离子的n壳层时RR截面随自由电子能量的变化,以及原子实对这种变化的影响;给出了两种理论模型下RR截面曲线变化的差异,并对这种差异做了较详细的理论说明.