MO-PPV/ZnSe量子点复合材料的制备及光致发光特性研究

采用水相法制备了颗粒尺寸为3.75nm的硒化锌(ZnSe)量子点,采用表面活性剂将ZnSe量子点转移到有机相聚(2-甲氧基-5-辛氧基)对苯乙炔(MO-PPV)中,获得了MO-PPV/ZnSe复合材料。通过对MO-PPV和ZnSe量子点的吸收光谱(ABS)和光致发光(PL)光谱的研究发现,随着ZnSe量子点掺杂浓度的提高,复合材料的发光强度明显增强,发光峰位置出现了蓝移。当ZnSe∶MO-PPV的质量比为1∶0.181时,发光峰位置蓝移10nm。结果表明,MO-PPV与ZnSe量子点之间存在着能量传递,这是导致MO-PPV/ZnSe量子点复合材料具有PL增强的重要原因。     

PbS量子点的化学溶液法制备技术

在Zhang制备PbS量子点技术的基础上,作者对其技术进行了改进,通过引入溶剂和反应添加剂,在室温,常压下合成了PbS量子点.由于该改进技术可通过选择不同种类的溶剂、不同种类的添加剂、不同的反应物浓度以及不同的反应时间,来控制PbS量子点的尺寸及表面形貌,这为化学溶液法室温制备PbS量子点带来了极强的可控性.这种廉价实用的室温、常压量子点制备技术在量子点红外探测器、生物标签,有机/无机复合材料等材料与器件等领域有潜在的应用价值.     

基于无杂质空位混杂法制备带有无吸收窗口的940nm GaInP/GaAsP/GaInAs半导体激光器研究

为提高940nm半导体激光器抗灾变性光学损伤(COD)能力,采用无杂质空位量子阱混杂技术制备了带有无吸收窗口的940nm GaInP/GaAsP/GaInAs半导体激光器。借助光致发光光谱分析了退火温度和介质膜厚度对GaInP/GaAsP/GaInAs单量子阱混杂的影响;通过电化学电容-电压(EC-V)方法检测了经高温退火后激光器外延片的掺杂浓度分布的变化情况。实验发现,在875℃快速热退火条件下,带有磁控溅射法制备的200nm厚的SiO2盖层样品发生蓝移达29.8nm,而电子束蒸发法制备的200nm厚TiO2样品在相同退火条件下蓝移量仅为4.3nm。两种方法分别对蓝移起到很好的促进和抑制作用。将优化后的条件用于带有窗口结构的激光器器件制备,其抗COD能力提高了1.6倍。     

ZnCdS/Cd_xZn_(1-x)Se_yS_(1-y)量子点量子阱及有机-无机LED北大核心

为了提高无机纳米发光材料的发光效率和有机-无机杂化电致发光器件的性能,使用有机金属前驱体法,制备了具有化学组分梯度的ZnCdS/CdxZn1-xSeyS1-y量子点量子阱材料以及CdxZn1-xSeyS1-y量子点材料。观察到相同反应温度与反应物配比所制得的ZnCdS/CdxZn1-xSeyS1-y光致发光峰相较于CdxZn1-xSeyS1-y出现明显的蓝移,且荧光量子效率有一定的提高,最高可达60.6%。通过在反应过程中调节Se与S的比例,观察到了反应产物的光致发光峰随Se比例的减少而逐渐蓝移。结果表明,与使用纯无机纳米材料作为有源层的器件相比,使用量子点量子阱材料制备的有机-无机杂化LED的电流效率提高了4.3倍。     

立方ZnMgO基体中六方ZnO量子点的化学溶液制备技术

首次报道了利用相分凝技术在非晶石英衬底上立方ZnMgO基体中制备六方ZnO量子点的化学溶液方法.对所制备的ZnO/ZnMgO/SiO2进行了原子力显微镜(AFM)、X射线衍射(XRD)、光致发光(PL)、椭圆偏振光谱(SE)表征.XRD表征表明当六配位Zn2 以替位的形式取代六配位Mg2 时,会导致相同衍射条件下立方ZnMgO的2θ比立方MgO的2θ小.SE表征发现ZnO量子点的量子效应导致了ZnO量子点的激子吸收能(3.76eV)比ZnO体晶的能带隙(3.37 eV)大.AFM表征表明:导致薄膜的XRD的衍射峰、α吸收峰和PL发射峰皆很宽的部分原因是由于组成所制备薄膜的晶粒尺寸分散较大、形状不一引起的.     

基于化学溶液法制备的氧化锌量子点发光二极管研究

氧化锌（ZnO）量子点是一种宽直接带隙半导体纳米颗粒,具有激子束缚能大、绿色环保、量子效应等优点,引起广泛关注。近期,将通过化学溶液法制备的ZnO量子点应用到发光二极管的研究成为热点。文章综述了近几年ZnO量子点发光二极管研究进展,重点介绍了各种结构的ZnO量子点发光二极管最新研究成果,并对ZnO量子点发光二极管的发展趋势进行了展望。     

石墨烯量子点/介孔SiO2复合材料的研究进展

石墨烯量子点/介孔SiO2复合材料的发光效率是影响其应用的重要指标,文章从实验和理论两个方面总结了量子点/介孔复合材料发光效率的研究现状,分析了其发光效率的影响因素和理论预测方法,提出了建立石墨烯量子点/介孔SiO2复合材料发光效率模型的方法和亟待解决的关键问题。     

ZnO量子点的制备及其光电性能研究进展

概述了ZnO量子点的基本制备方法及生长特点,着重回顾了目前量子限制效应对ZnO量子点光电性能影响的研究进展。     

Cu掺杂对ZnO量子点光致发光的影响

通过溶液法合成了Cu掺杂ZnO量子点。X射线衍射(XRD)和高分辨电子透射电镜(HRTEM)图像显示Cu掺杂ZnO量子点具有六角纤锌矿结构,晶粒大小为4～5nm。Cu掺杂抑制了ZnO量子点颗粒长大。室温光致发光(PL)谱观察到紫外带边和可见区两个发射峰。随着Cu掺杂浓度的增大,紫外荧光峰位发生缓慢红移,由366nm移到370nm;可见区发射峰位发生蓝移,由525nm移到495nm;同时,两个发射峰强度降低。光谱结果表明:Cu的掺入,一方面抑制表面与O空位有关的缺陷,在495nm出现了与Cu1+有关的发射峰;另一方面,Cu离子掺入ZnO量子点引入一些非辐射中心,降低了自由激子发射。     

二氧化硅覆盖退火增强磷化铟基体激光器材料的量子阱混合

我们对SiO2覆盖退火增强InGaAs/InGaAsP/InP激光器材料量子阱混合技术进行了实验研究.相对于原始样品,退火时无SiO2覆盖的样品经800℃,30s快速退火后,其光致发光谱的峰值波长“蓝移”了7nm,退火时有SiO2覆盖的样品经过同样的快速退火后,其光致发光谱的峰值波长“蓝移”了56nm.即在同一片子上实现了在需要量子阱混合的区域带隙的“蓝移”足够大的同时,不希望量子阱混合的区域能带结构的变化创记录的小.本文认为增大量子阱的宽度、采用无应力的量子阱结构以及引入足够厚的缓冲层可以改善量子阱材料的晶格质量,有利于提高量子阱混合技术的可靠性与重复性,     

基于ZnS/SiO2量子点的EL器件及宽谱发射

将ZnS/SiO2量子点与PVP在甲醇溶液中充分混合作为活性层材料,通过匀胶方法制备了ITO//ZnS/SiO2∶PVP//Al结构的电致发光(EL)薄膜器件。器件的EL光谱由510～560nm波段的绿光发射和相对较弱的蓝紫光(400nm左右)发射组成,通过对发光光谱的分析发现,上述两个区域的发射均来自ZnS的缺陷能级。其中,绿色发光峰来源于较低能态的缺陷能级;而高能区域的蓝色发光则是由于高能态的缺陷能级俘获电子的几率增大,在这过程中,PVP形成的能级阶梯有效增加了高能态缺陷能级俘获电子的几率,提升了高能波段的发光效率,相应地,器件的色坐标也随之从(0.37,0.42)变化到(0.30,0.34),趋于白光发射。     

InGaN/GaN多量子阱LED电致发光谱中双峰起源的研究

研究了MOCVD生长的具有双发射峰结构的InGaN/GaN多量子阱发光二极管(LED)的结构和发光特性.在透射电子显微镜(TEM)下可以发现量子阱的宽度不一致,电致发光谱(EL)发现了位于2.45eV的绿光发光峰和2.81eV处的蓝光发光峰.随着电流密度增加,双峰的峰位没有移动,直到注入电流密度达到2×104 mA/cm2时,绿光发光峰发生蓝移,而蓝光发光峰没有变化.单色的阴极荧光谱(CL)发现绿光发射对应的发光区包括絮状区域和发光点,而蓝光发射对应的发光区仅包含絮状区域.通过以上的结果,我们认为蓝光发射基本上源于InGaN量子阱发光,而绿光发射则起源于量子阱和量子点的发光.     

The UV and blue light emission properties of Mn doped ZnO nanocrystals

We present a study of the light emission properties over wavelengths from UV to blue of Mn doped ZnO nanocrystals fabricated by means of a thermal evaporation vapor phase deposition process. The samples were grown with a Mn mole ratio in the Zn/Mn mixed source of 0% (pure ZnO sample, used as a reference), 5%, 10%, or 15% in a constant O₂/Ar gas mixture flowing at 500 °C. The pure ZnO nanocrystals exhibited a strong and predominantly UV emission peaking at 377 nm. In the photoluminescence spectra of mixed ZnO:Mn nanocrystals the major UV emission shifts from 377 to 408 nm, and a strong blue emission appears at 435 nm. The former is mainly induced by the impurity levels of Mn introduced in the band gap of the ZnO nanocrystals, while the latter is closely related to defect and Mn²⁺ ions. With increasing Mn concentration the blue emission is enhanced due to the strong exchange interaction in the short range spin system and the excess impurities on the surface. The results show that the optical properties of ZnO can be tuned by the doping concentration of Mn. Mn doped ZnO nanocrystals with strong blue emission can be used in the fabrication of blue light devices.     

MgO界面层对n-ZnO纳米棒/p-GaN异质结LED光电性能的影响

为了较好地实现n-ZnO的电致发光(EL),利用水热法在p-GaN外延片上制备了ZnO纳米棒阵列,构造了n-ZnO纳米棒/p-GaN异质结LED原型器件,并研究了MgO界面层对器件光电性能的影响。结果表明,n-ZnO纳米棒/p-GaN异质结器件具有明显的二极管整流效应。室温、正向偏压下,n-ZnO纳米棒/p-GaN异质结LED仅在430nm附近具有单一的发光峰,而n-ZnO纳米棒/MgO/p-GaN异质结LED的电致发光光谱由一个从近紫外到蓝绿光区的宽发光带组成。结合光致发光(PL)谱和Anderson能带模型,深入分析了n-ZnO纳米棒/p-GaN异质结的载流子复合机制。     

Near-Ultraviolet Light-Emitting Devices Using Vertical ZnO Nanorod Arrays

Reports on electroluminescence (EL) in solid-state, nanomaterial-based devices emitting in the lower wavelength range of the visible spectrum are limited, and the emission stability of these devices is rarely reported. We have fabricated light-emitting devices (LEDs) based on integration of n-ZnO nanorods and p-GaN films, which emit in the violet to near-ultraviolet (NUV) region. We also present data on the stability of EL in fabricated devices. Vertical arrays on ZnO nanorods, with estimated ZnO nanorod density ~10⁸ cm⁻², were grown on p-GaN films with typical length of ~4 μm and width of ~120 nm. The NUV LEDs show low turn-on voltage (~3.0 V), small reverse saturation current (~10 μA), and more than two orders of magnitude rectification ratio, all of which indicates a good-quality p–n junction at the p-GaN/n-ZnO nanorod interface. The EL spectra of LEDs present an emission band centered at ~403 nm. Gaussian fitting of the EL peak revealed three emission peaks at 378 nm, 405 nm, and 431 nm with dominant emission in the NUV region. Significantly, the fabricated NUV LEDs present stable and repeatable EL characteristics, as revealed by bias-stress stability tests. The good electrical properties and stable EL performance make these nanostructure-based NUV LEDs potential candidates for mass production of next-generation lighting devices.     

White electroluminescence from ZnO/GaN structures

White electroluminescence (EL) from ZnO/GaN structures fabricated by pulsed laser deposition of ZnO:In onto GaN:Mg/GaN structures MOCVD-grown on Al₂O₃ substrates has been observed. The white light is produced by superposition of the two strongest emission lines, narrow blue and broad yellow, peaked at 440 and 550 nm, respectively. The intensity ratio of different EL lines from ZnO/GaN/Al₂O₃ structures depends on the ZnO film quality and drive current. The white EL is due to the high density of structural defects at the n-ZnO/p-GaN interface. A band diagram of the n-ZnO/p-GaN/n-GaN structure is constructed and a qualitative explanation of the EL is suggested.     

有机无机复合膜发光器件的研究

针对聚合物电致发光（EL）材料缺乏可用的电子型聚合物半导体材料的现状，采用无机电子型半导体材料ZnO：Zn与空穴型聚合物材料poly（2，5bis（dodecyloxy）-phenylenevinylene）（PDDOPV）成功制备了结构为ITO／PDDOPV／ZnO：Zn／Al的有机／无机复合膜双层器件。复合膜器件的发光效率与亮度比单层器件提高了1个数量级以上，而复合膜的电流是单层器件的0．5倍。而且，聚合物／无机物复合膜器件的发光颜色随电压的增加而蓝移，其光致发光（PL）光谱也随激发波长的改变而改变，有可能形成了新的发光基团。     

8-羟基喹啉锂蓝色有机电致发光器件

合成了蓝色有机薄膜电致发光材料8-羟基喹啉锂(Liq),8-羟基喹啉锂薄膜的PL光谱峰位于475nm^2分析了8-羟基喹啉锂发射光谱蓝移的原因^2制备了两种结构的蓝色发光器件,其最高亮度分别为1200cd／m^2和2000cd／m^2,EL峰位于490nm^2用能级图比较和分析了两种器件的特性。     

Metal-anode-dependent spectra and efficiency in blue top-emitting organic light-emitting devices

In this study, the blue top-emitting organic light-emitting devices (TEOLEDs) with different metal anodes are fabricated. The effect of different anode materials on the spectra and efficiency of blue TEOLEDs is studied. We demonstrate that Al is a more suitable anode material for blue TEOLEDs due to its larger phase shift on reflectance (PSR) than the other common metal materials, such as Ag and Au. The influence of light outcoupling layer (LOL) on the transmittance and PSR of cathode is also investigated to obtain the optimum condition for devices. Angle-independent electroluminescence (EL) spectra are obtained in blue TEOLEDs for each metal anode but the device with Al anode possesses higher efficiency and much thicker organic layers, which is beneficial to the lifetime of the device. These results offer a practicable platform for the realization of TEOLEDs based full-color displays and lightings.