Self-heating dependent characteristic of GaN-based light-emitting diodes with and without AlGaInN electron blocking layer

In this study, GaN-based light-emitting diodes （LEDs） with and without A1GaInN electron blocking layer （EBL） under self-heating effect are numerically studied. The energy band diagram, carrier transport and distribution characteristics, internal Joule heat and non-radiative recombination heat characteristics, and internal quantum efficiency are investigated. The effect of Auger recombination coefficient on efficiency droop under self-heating effect is also studied. The simulation results show that efficiency droop is markedly improved when an AlGaInN EBL is placed between p-type GaN layer and active region. However, the chip temperature of LED is significantly increased simultaneously. The results also indicate that Auger recombination can be neglected because it is not the major contributor for the internal heat source. The efficiency droop is unrelated to the internal heat source. However, both electron leakage and Auger recombination play important roles in efficiency droop mechanism under self-heating effect.     

低In组分量子阱垒层AlGaN对GaN基双蓝光波长发光二极管性能的影响

采用数值分析方法对含有低In组分AlGaN垒层InGaN/GaN混合多量子阱双蓝光波长发光二极管进行模拟分析. 结果表明，这种AlGaN量子阱垒层能有效改善电子和空穴在混合多量子阱活性层中的分布均匀性及减少电子溢出，实现电子空穴在各个量子阱中的平衡辐射，从而减弱了双蓝光波长发光二极管的效率衰减. 此外，通过改变AlGaN量子阱垒层的Al组分，可以调控双蓝光波长发光二极管发射光谱的稳定性:当Al组分为0.08时，双蓝光波长发光二极管的光谱在小电流和大电流下都比较稳定，而Al组分为0.09时，光谱只在40~100 mA电流范围内比较稳定.     

Advantage of dual wavelength light-emitting diodes with dip-shaped quantum wells

Dual-wavelength light-emitting diodes (DW-LEDs) with dip-shaped quantum wells have been studied by numerical simulation.The emission spectra,light output power,carrier concentration in the quantum wells and internal quantum efficiency are investigated.The simulation results indicate that the DW-LEDs with dip-shaped quantum wells perform better than conventional LEDs with rectangular quantum wells in terms of light output power,leakage current and efficiency droop.These improvements in the electrical and optical characteristics are mainly attributed to the alleviation of the electrostatic field in the dip-shaped quantum wells.     

垒层p型掺杂量的分布对InGnN基发光二极管性能的影响

采用APSYS软件分析了InGaN基发光二极管的垒层中p型掺杂量的分布及作用.研究结果表明当所有的p型掺杂量集中于最后一个垒层时，发光二极管的发光强度最大，大注入电流下的效率衰减量最小.其主要原因为优化垒层中p型掺杂量的分布有利于电子限制和空穴注入.     

多量子阱垒结构优化提高GaN基LED发光效率研究

为了解决由于极化效应引起的漏电流影响发光效率的问题,以k.p理论为基础建立多量子阱模型,分析研究了GaN基LED中不同的InGaN/InGaN多量子阱发光层势垒结构.基于化合物半导体器件的电学.光学和热学属性的有限元分析,设计与优化多量子阱中靠近P型AIGaN电子阻档层倒数第二层势垒,显著提高了光输出功率,减少漏电流.数值模拟分析表明,改良多量子阱势垒能够大幅提高高亮度,高功率器件结构光电特性.     

LiF用作阴极注入层的有机发光二极管制备

使用真空热蒸发方法,制备了结构为ITO/TPD/Alq3/LiF/Al的有机发光二极管,其中LiF用作阴极注入层,LiF超薄层的加入,增强了电子注入,降低了启亮电压,提高了器件的发光效率和亮度. 实验结果表明:当加入LiF层的厚度为0.5 nm时,器件性能的改善最好,和不含LiF的器件相比,启亮电压由原来的9 V降低到5 V,效率由1.5 cd/A增加到3.3 cd/A,提高了近1倍,然而随着加入LiF层厚度的增加,器件性能的改善效果降低.     

InGaN/GaN耦合量子阱结构光电性质改善的物理机制

利用数值模拟方法,研究InGaN/GaN耦合量子阱结构光电性质相对传统量子阱结构光电性质改善的物理机制。模拟结果显示,与InGaN/GaN传统量子阱相比,耦合量子阱结构的电压 电流特性得到有效改善,获得较高发光强度和光输出功率。其光电性质改善的主要机制是:InGaN/GaN耦合量子阱结构能够减小电场强度、势垒高度和厚度,从而加强阱中载流子隧穿效应,改善有源区载流子分布均匀性,同时,阱层中电子 空穴波函数重叠率也得到提高。     

GaN基Micro-LED量子效率的研究进展

微米级发光二极管（Micro light-emitting diode, Micro-LED）器件具有高亮度、高耐热性、长寿命、低功耗以及极短的响应时间等优点,被视为下一代显示技术的基石,可满足手机、可穿戴手表、AR/VR、微型投影仪、超高亮度显示器等先进设备应用的个性化需求。Micro-LED显示芯片与目前用于高亮度照明的无机半导体芯片具有相似的特性。当管芯直径减小到微米级时,会出现尺寸效应与Droop效应,量子效率急剧下降,器件整体性能受限。介绍了发光二极管的量子效率及影响GaN基Micro-LED量子效率的因素,并提出提升内量子效率和光提取效率的措施,同时对Micro-LED的未来研究与应用进行了总结与展望。     

双重优化对基于P3HT:PCBM有机太阳能电池效率的提高

有效提高太阳能电池对光的吸收效率是提高太阳能电池能量转换效率的重要因素.在以poly(3-hexylthiophene)(P3HT)为电子给体材料,[6,6]-phenyl C60-butyric acid methyl eater(PCBM)为电子受体材料的有机太阳能电池中,Poly-(3,4-ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS)与活性层之间插入不同厚度的P3HT层,并在P3HT层最佳厚度的基础上,进一步在活性层中掺杂不同比例的Ag纳米粒子,双重优化了电池器件.当插入45 nm的P3HT层及掺杂质量比为5%的Ag纳米粒子时活性层薄膜的形貌及内部结构得到了改善,电池对光的吸收,及外量子效率得到了显著地提高,并出现红移现象.在25°C,光强为100 mW/cm2的条件下测量其短路电流密度JSC为11.21 mA/cm2,能量转化效率PCE为3.79%.     

新型铅卤基钙钛矿材料及其应用

铅卤基钙钛矿材料因其优异的光电转化效率、可调禁带宽度、较高载流子迁移率、较大光吸收系数等突出性能,在太阳能电池、发光器件和光电探测等领域获得广泛关注。介绍了铅卤基钙钛矿薄膜、量子点和单晶的制备和相关物理性能,总结了其在太阳能电池、发光二极管(LED)、光电探测器等领域的最新研究进展,讨论了目前存在的问题及未来发展前景。     

量子点敏化太阳能电池ZnO光阳极的制备及性能

先用水热法合成ZnO颗粒, 再用溶胶 凝胶法将ZnO颗粒制备成量子点敏化太阳能电池光阳极, 并通过X射线衍射(XRD)、 扫描电子显微镜(SEM)、 透射电子显微镜(TEM)、 紫外-可见吸收光谱(UV-Vis)和光电流密度 电压曲线分析不同厚度的六方纤锌矿型ZnO光阳极对量子点敏化太阳能电池性能的影响. 结果表明, 增加量子点的吸附面积可使ZnO光阳极的UV-Vis谱吸收带边红移, 进而提升太阳能电池的光电转换效率.     

Near infrared polymer light-emitting diodes

High efficiency of near infrared polymer light-emitting diodes with bilayer structure was obtained. The diode structure is ITO/PEDOT/LI/L2/Ba/Al, where L1 is phenyl-substituted poly [p-phenylphenylene vinylene] derivative (P-PPV), L2 is 9,9-dioctylfluorene (DOF) and 4,7-bis(3-hexylthiophen)-2-yl-2,1,3-naphthothiadiazole (HDNT) copolymer (PFHDNTI0). The electroluminescence (EL) spectrum of diodes from PFHDNTI0 is at 750 nm located inthe range of near infrared. The maximum external quantum efficiency is up to 2.1% at the current density of 35 mA/m^2. The improvement of the diode‘s performances was considered to be the irradiative excitons confined in the interface between L1 and L2 layers.     

Progress in photonic and optoelectronic active polymers and organic solids

The progress of the researches in photonic and optoelectronic active polymers and organic solids in recent two decades is reviewed with particular attention to the excellent achievements of Chinese scientists. The recent progress in the areas of conducting polymers, organic light-emitting diodes, photoelectric conversion material, material for information storage, and nonlinear optical polymers is introduced. The peculiarities of organic photonic and optoelectronic active materials are briefly compared with those of inorganic photonic and optoelectronic materials.     

New BaBrCl： Eu^2＋ phosphors for X-ray image recording

Photostimulated luminescence （PSL） is observed in BaBrCl： Eu^2＋after X-ray irradiation at room temperature. It is suggested by PSL stimulation spectrum and difference absorption spectrum （DAS） that F centers are formed upon X-ray irradiation and both spectra show two bands which are centered at about 550 nm and 675 nm respectively. This enables the use of semiconductor light-emitting diodes （LED） instead of gas lasers for photostimulation. The PSL intensity increases linearly with X-ray irradiation dose increasing, and the conversion efficiency is 29% that for the standard commercial storage phosphor BaFBr：Eu from Fuji imaging plate.     

M-PS-S结构的V-I特性及其优化

选用n-，p-和p+三种半导体硅材料作为衬底，通过电化学腐蚀方法分别形成PS薄膜；在PS／S膜上再淀积一层具有一定图形的铝金属膜并焊接引线，形成了M－PS－S二极管结构；在外加直流偏置电压下分别测量它们的V－I特性，得出了不同的V－I特性曲线；V-I特性都具有整流效应．根据对所得特性的理论分析．论述了材料、工艺和结构等因素对M－PS－S特性的影响．并提出了优化设计的方法，以改善M－PS－S结构的特性，实现其在发光、敏感等方面的应用。     

顶发射白光有机电致发光器件的优化

为满足大面积固态照明与全彩显示的需求,实现色度稳定的高效率顶发射白光有机电致发光器件,采用仿真和实验相结合的研究方法,模拟基于光学传输矩阵法和电磁场理论进行计算,用真空蒸镀法制备器件并测试其光电性能。确定传输层材料、厚度和结构,优化发光效率,逐步改进发光层结构,以改善器件的效率和颜色质量。结果表明,基于电学平衡的P-I-N传输结构和蓝/红/蓝三明治型发光结构,能实现色度稳定的高效率顶发射白光有机电致发光器件。     

量子点敏化太阳能电池ZnO光阳极的制备及性能

先用水热法合成ZnO颗粒, 再用溶胶 凝胶法将ZnO颗粒制备成量子点敏化太阳能电池光阳极, 并通过X射线衍射(XRD)、 扫描电子显微镜(SEM)、 透射电子显微镜(TEM)、 紫外-可见吸收光谱(UV-Vis)和光电流密度 电压曲线分析不同厚度的六方纤锌矿型ZnO光阳极对量子点敏化太阳能电池性能的影响. 结果表明, 增加量子点的吸附面积可使ZnO光阳极的UV-Vis谱吸收带边红移, 进而提升太阳能电池的光电转换效率.     

Flexible organic light-emitting diodes with poly-3, 4-ethylenedioxythiophene as transparent anode

The flexible oragnic light-emitting diodes (OLEDs) fabricatedon poly-3, 4-ethylenedioxythiophene/polystyrenesulfonate (PEDOT/PSS) coated substrates were demonstrated. How the fabricating processes and the device structure will affect the device performance was studied and the atomic force microscopy was employed to analyze the mophorlogy of the conducting polymer anode. Under optimized conditions, flexible OLEDs with PEDOT anode showed the brightness up to 2760 cd/m² and maximum external quantum efficiency of 1.4%. These data are comparable to those of conventional flexible OLEDs with ITO anode.     

A dye-sensitized solar cell based on PEDOT:PSS counter electrode

A counter electrode for dye-sensitized solar cell (DSSC) was prepared by coating poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) with high transparency and adhesion on a conducting FTO glass at low temperature. The surface morphology, conductivity, sheet resistance, redox properties and photoelectric properties of the PEDOT:PSS/carbon electrodes were observed using scanning electron microscopy, a four-probe tester and a CHI660D electrochemical measurement system. The experimental results showed that DSSCs had the best photoelectric properties for PEDOT:PSS/carbon counter electrodes annealed at 80°C under vacuum conditions. The overall energy conversion efficiency of the DSSC with PEDOT:PSS/carbon counter electrode and barrier layer reached 7.61% under irradiation from a simulated solar light with intensity of 100 mW/cm² (AM 1.5). The excellent photoelectric properties, simple preparation procedure and low cost allow the PEDOT:PSS/carbon electrode to be a credible alternative electrode for use in DSSCs.     

晶体硅太阳电池的氮化硅表面钝化研究

为了提高晶体硅太阳电池的光电转换效率，研究了用等离子增强化学气相沉积（PECVD）的SiNx：H作为晶体硅太阳电池的表面钝化及减反射膜对电池性能的影响，并采用不同的工艺路线制备了不同类型的电池。实验发现：同SiNx：H比较，SiNx:H/SiO2双层光学减反射结构对晶体硅太阳电池能起到更加有效的表面钝化作用，提高了太阳电池的光电转换效率。基于界面物理，提出了一种新的能带模型，解释了用不同实验方法制作的晶体硅太阳池性能的差异。