GaP表面粗化对AlGaInP发光二极管光电特性的影响

采用湿法溶液粗化AlGaInP基红光LED表面GaP层 ,并在粗化后的GaP表面沉积ITO,研究了粗化时间对GaP表面形貌的影响,并利用SEM、半导 体 芯片测试机、X射线衍射仪、X射线光电子能谱对LED器件表面形貌、光电特性曲 线、界面晶向、元素特性进行表征,比较了粗化前后的LED亮度和光电特性变 化。测试结果表明:采用HIO₄、I₂、HNO₃系列粗化液在室温、粗化时间为30 S 时,有效增加了光在通过GaP面与ITO界面时的出光角度,使AlGaInP发光二极管 的发光效率提高21.4%,同时引起界面处的缺陷密度升高,费米能级 远离价带,主波长蓝移0.36 nm,正向电压上升0.04 V。     

薄膜AlGaInP发光二极管中光子吸收的研究

分析了薄膜发光二极管中光子的路径,对比了AlGaInP薄膜发光二极管的反光镜有无AlGaInP层的反射率,分析了AlGaInP层的吸收并计算了光提取效率。制作了不同GaP厚度的TF AlGaInP LED。在20mA的驱动电流下,0.6μm GaP的LED比8μm GaP 的LED光输出功率高33％。提出了在0.6μm GaP的LED中腐蚀去除非欧姆接触点处的重掺GaP。在n型电极和p型欧姆接触点间的电流扩展的设计和优化需要更进一步的研究。     

薄膜AlGaInP发光二极管中不同反光镜的研究

本文计算了GaP/Au 反光镜, GaP/SiO2/Au 三层ODR and GaP/ITO/Au 三层ODR的反射率随角度的变化值。制作了GaAs衬底的AlGaInP LED,Au反光镜、SiO2 ODR和ITO ODR的薄膜AlGaInP LED。在20mA下,四种样品光输出功率分别为1.04mW, 1.14mW, 2.53mW and 2.15mW。制作工艺退火后,Au扩散使Au/GaP反光镜的反射率降至9％。1/4波长的ITO和SiO2透射率不同造成了两种薄膜LED光输出功率不同。ITO ODR中加入Zn可以大大降低LED的电压,但并不影响LED的光输出。     

非平面化型ITO氮化镓基蓝光发光二极管

将氧化铟锡(ITO)生长于氮化镓基蓝色发光二极管的出光台面上(p型GaN台面),用非平面化处理的方法制作出ITO井状结构,研制出非平面化型氧化铟锡-氮化镓基蓝色发光二极管(LED),获得了高的出光效率.结果表明,在20mA工作电流下,该蓝色发光二极管的出光光强是平整的普通ITO-GaN基LED的1.35倍.     

AlGaInP橙色发光二极管的研制

利用ＬＰ－ＭＯＣＶＤ外延生长ＡｌＧａＩｎＰＤＨ橙色发光二极管，２０ｍＡ工作条件下发光波长峰值在６２８ｎｍ，ＦＷＨＭ为２６ｎｍ，１５°（２θ１／２）视角封装后亮度达到３１０ｍｃｄ；８０ｍＡ工作条件下亮度达到１０００ｍｃｄ。并且分析了生长过程中杂质向有源区扩散对发光光谱的影响。     

带有周期性微结构的InGaAlP量子阱发光二极管

在分析和研究圆盘型光学模式的基础上,本文提出并研制成功一种带有周期性环形沟槽结构的新型InGaAlP量子阱发光二极管.这种LED的制备工艺简单易行,效果明显.结果证实,与同样面积方形台面普通LED相比,这种LED的出光强度和效率都得到明显的增强和提高,为改进发光二极管的性能提供了一条新途径.     

透明导电ITO欧姆接触的AlGaInP薄膜发光二极管

提出了一种透明导电氧化铟锡(ITO)欧姆接触的AlGaInP薄膜发光二极管(LED)的结构和制作工艺.在这个结构里,ITO还作为窗口层材料,增强电流扩展,并应用了高反射率的金属作为反光镜.用Au-Sn合金(Au∶Sn＝8∶2,重量比)作为焊料,把带有金属反光镜的AlGaInP LED(RS-LED)外延片倒装键合到GaAs基板上,并去掉外延GaAs衬底,把被GaAs衬底吸收的光反射出去.与常规AlGaInP吸收衬底LEDs(AS-LED)和带有分布布拉格反光镜(DBR)的AlGaInP吸收衬底LEDs(DBR-AS-LED)电、光特性的比较,用透明导电ITO做欧姆接触的AlGaInP薄膜RS-LED结构能极大提高光输出功率和发光强度.正向电流20 mA时,RS-LED的光输出功率分别是AS-LED和DBR-AS-LED的2.4倍和1.7倍;RS-LED 20 mA下峰值波长624 nm的轴向光强达到了179.6 mcd,分别是AS-LED 20 mA下峰值波长627 nm和DBR-AS-LED 20 mA下峰值波长623 nm轴向光强的2.2倍和1.3倍.     

提高发光二极管出光效率的新方法

利用高分子共混物的微相分离和自组装原理,制备出具有纳米微孔的PMMA薄膜,以此为掩膜对发光二极管(LED)表面进行湿法腐蚀,得到表面微结构,并研究了腐蚀时间对表面形貌的影响.测试结果表明,当微孔直径在500 nm左右、腐蚀深度约140 nm时,所得到的表面微结构能使LED在20 mA的注入电流下光功率平均提高18%.     

用微结构压印提高GaN基发光二极管的输出光强

为了进一步提高GaN基发光二极管(LED)的出光效率,针对倒装焊GaN基发光二极管提出了一个在蓝宝石衬底出光面上引入二维微纳米阵列结构的新构想.根据这一构想,将微结构图形化压印和发光器件的封装有机地结合起来,利用一种简易可行的纳米压印-热硬化性聚合物压印技术,成功地制备出了带有微米级阵列超薄封装结构的LED.结果表明,这种带有微结构阵列LED的输出光强得到了明显增强,1mm×1mm大管芯GaN LED在350mA的直流电注入下的光功率比无微结构的LED提高了60%.这一成功为提高发光二极管的出光强度提供了一个有效的新途径.     

WO3/NiWO4复合薄膜的制备及其光电化学性能

采用两步水热法在导电玻璃(FTO)上制备了WO₃/NiWO₄复合薄膜。通过XRD,SEM表征了WO₃/NiWO₄复合薄膜的组成结构及微观形貌,利用UV-Vis、光电流测试、光电催化测试和交流阻抗测试分析了WO₃/NiWO₄复合薄膜的光电性能。结果表明:WO₃/NiWO₄复合薄膜相较于WO₃薄膜具有更好的光吸收特性、光电流密度和光电催化活性,其中水热反应3h的WO₃/NiWO₄复合薄膜的光电化学性能最佳。WO₃/NiWO₄-3h在1.4V(vs.Ag/AgCl)时的光电流密度为1.94mA/cm²,光电催化210min对亚甲基蓝溶液的降解效率为57.1%。交流阻抗图谱表明WO₃/NiWO₄薄膜的电荷转移电阻小于WO₃薄膜,光电化学性能更优。     

WO3/SnO2复合薄膜的制备及光电性能

采用水热法和电化学沉积法,成功制备了包覆有SnO₂纳米颗粒的WO₃纳米棒阵列薄膜,退火处理后形成WO₃/SnO₂异质结复合薄膜。通过改变SnO₂的沉积时间得到了复合薄膜的最佳制备条件。采用XRD,FESEM对WO₃/SnO₂复合薄膜的物相和形貌进行了分析,通过电化学工作站对WO₃/SnO₂复合薄膜的光电性能进行了研究,结果表明,电沉积时间为120 s时,WO₃/SnO₂复合薄膜具有最小的阻抗,且在0.6 V的偏压下光电流密度为0.46 mA/cm²,相比于单一WO₃纳米棒薄膜,表现出更好的光电化学性能。     

石墨烯掺杂Cs2CO3作为高效电子注入层的OLEDs性能研究

研制了石墨烯掺杂Cs₂CO₃(Cs₂CO₃:Graphe ne )作为高效电子注入层、结构为ITO/N,N′-bis-(1-naphthyl) -N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine (NPB)(50 nm)/tris-(8-hydroxy quinoline)-aluminum Alq₃(80 nm)/Cs₂CO₃:Gra phene (mss 20% 1nm)/Al(120 nm)的OLEDs。将其与标准器件ITO/NPB(50 nm)/Alq₃(80 n m)/LiF(0.5 nm)/Al(120 nm)作性能比较,研究石墨烯掺杂在Cs₂CO₃中作为电子注入层 对 OLEDs性能的影响。结果表明,基于Cs₂CO₃:Graphene结构作为电子注入层的器 件效率要高于LiF作为电子注入层的器件,其最大电流效率达到2.02 cd/A, 是标准器件的2.59倍;亮度也高于LiF作为电子注入层的器件,在10 V时达 到最大值7690cd/m²,是标准器件最大亮度 的2.07倍。性能得到提高的主要机理是由于Cs₂CO₃:Graphene的引入提高了电子注入效率。     

基于涂覆Pd/WO3膜的长周期光纤光栅氢气传感器设计

氢气浓度的高精度、快速监测在众多领域具有重 要意义。本文提出一种基于涂覆Pd/WO₃膜的长周期光纤光栅氢气浓度传感器。首先研究了 镀Pd/WO₃膜的LPFG对氢气的传感特性,利用光学仿真软件模拟了薄膜折射率在1. 99范围内的传感情况,仿真结果表明当氢气浓 度增加时,Pd/WO₃薄膜折射率降低,LPFG透射谱谐振波长蓝移,谐振波长偏移对Pd/WO₃薄膜 折射率变化的灵敏度为256.9 nm/RIU。为了增强镀膜LPFG氢气传感器 的灵敏度,进一步研究 了包层半径及周期对其谐振波长灵敏度的影响,结果表明LPFG的谐振波长灵敏度随周期Λ的 增大而增加;在相同周期的条件下,包层半径越小,谐振波长的偏移值越大,该研究对开发 高灵敏度可复用的光纤氢气传感器具有重要指导意义。     

Efficiency enhancement of InGaN/GaN light-emitting diodes with a back-surface distributed bragg reflector

The design, fabrication, and performance characteristics of a back-surface distributed Bragg reflector (DBR) enhanced InGaN/GaN light-emitting diode (LED) are described. A wide reflectance bandwidth in the blue and green wavelength regions is obtained using a double quarter-wave stack design composed of TiO₂ and SiO₂ layers. More than 65% enhancement in extracted light intensity is demonstrated for a blue LED measured at the chip level. Similar improvement in green LED performance is discussed and achieved through simulation. Possible applications of back-surface DBR-enhanced LEDs include surface-mount packages with significantly reduced vertical profiles, resonant cavity LEDs, and superluminescent diodes.     

Highly flexible organic light-emitting diodes based on ZnS/Ag/WO3 multilayer transparent electrodes

We report our study on highly flexible organic light-emitting diodes based on ZnS/Ag/WO₃ (ZAW) multilayer transparent electrodes in which high conductivity and ductility of Ag layers allow for efficient sheet conduction and flexibility while ZnS and WO₃ layers provide a means for enhancement in optical transmission and/or carrier-injection. Devices with ZAW anodes fabricated on planarized plastic substrates not only exhibit a performance and operational stability comparable to or better than those of ITO-based devices but also show a mechanical flexibility that is far superior to that of ITO-based devices. Experimental results show that a consistent performance can be obtained in ZAW-based devices upon repeated bending down to a radius of curvature of 5 mm, below which the flexibility of the devices is limited ultimately by the delamination occurring at cathode/organic interfaces rather than by the ZAW electrodes themselves.     

表面结构和生长方向对WO3纳米线电子结构影响的第一性原理研究

The effects of the surface and orientation of a WO₃ nanowire on the electronic structure are investigated by using first principles calculation based on density functional theory（DFT）.The surface of the WO3 nanowire was terminated by a bare or hydrogenated oxygen monolayer or bare WO₂ plane,and the[010]- and[001]-oriented nanowires with different sizes were introduced into the theoretical calculation to further study the dependence of electronic band structure on the wire size and orientation.The calculated results reveal that the surface structure, wire size and orientation have significant effects on the electronic band structure,bandgap,and density of states （DOS） of the WO₃ nanowire.The optimized WO₃ nanowire with different surface structures showed a markedly dissimilar band structure due to the different electronic states near the Fermi level,and the O-terminated[001] WO₃ nanowire with hydrogenation can exhibit a reasonable indirect bandgap of 2.340 eV due to the quantum confinement effect,which is 0.257 eV wider than bulk WO₃.Besides,the bandgap change is also related to the orientation-resulted surface reconstructed structure as well as wire size.     

基于插入WO3缓冲层并五苯有机场效应晶体管性能的研究

The pentacene-based organic field effect transistor （OFET） with a thin transition metal oxide （WO3） layer between pentacene and metal （AI） source/drain electrodes was fabricated. Compared with conventional OFET with only metal AI source/drain electrodes, the introduction of the WO3 buffer layer leads to the device performance enhancement. The effective field-effect mobility and threshold voltage are improved to 1.90 em2/（V.s） and 13 V, respectively. The performance improvements are attributed to the decrease of the interface energy barrier and the contact resistance. The results indicate that it is an effective approach to improve the OFET performance by using a WO3 buffer layer.     

有机发光器件中空穴注入对负电容的影响

对不同结构的有机发光器件(OLED)进行了电容-电压(C-V)特性测量,研究了不同空穴注入结构对OLED负电容的影响。结果表明,负电容的产生与OLED内部电场的分布有着密切的关系,负电容开始出现的频率与电压的平方根呈指数关系。与超薄的单层空穴注入层相比,掺杂的空穴注入层不仅能降低器件的驱动电压,而且其载流子传输特性和出现负电容时的初始电压对频率有着更强的依赖性。     

Hole injection polymer effect on degradation of organic light-emitting diodes

Polythienothiophene:poly(perfluoroethylene-perfluoroethersulfonic acid) (PTT:PFFSA) has been used to enhance hole injection into small molecule OLEDs. Compared to devices with polyethylene dioxythiophene polystyrene sulfonate (PEDOT:PSS) as the hole injection layer (HIL), the OLED using PTT:PFFSA as a HIL gives enhanced efficiency and a slower luminance decay as well as a slower rise in operating voltage. Further studies of capacitance–voltage characteristics reveal that positive trapped charges accumulate in the hole transporting layer during operation. These results thus highlight the significance of hole injection layer to OLED operational stability.