CdSe/ZnS量子点光纤纤芯基底的研究

量子点光纤正逐渐成为光通信领域的研究热点。首先介绍了CdSe/ZnS量子点掺杂光纤的发展历史,随后给出两种不同纤芯基底材料的CdSe/ZnS量子点掺杂光纤的制备方法,并对它们的光谱特性及发射峰值增益进行了分析比较,最后分析得出适合CdSe/ZnS量子点掺杂光纤的纤芯基底材料。CdSe/ZnS量子点掺杂光纤基底材料的研究对其他量子点光纤的研制具有一定的借鉴作用。     

CdSe/ZnS和PbSe量子点光纤及光纤放大器研究进展

近年来,纳米晶体(量子点)以及量子点光纤、量子点光纤放大器成为一个研究热点。介绍了CdSe/ZnS和PbSe量子点的光谱特性以及量子点的吸收-辐射截面,表明量子点具有强的吸收和发射。总结了低浓度和较高浓度CdSe/ZnS量子点掺杂光纤、熔融法及溶胶凝胶法制备PbSe量子点光纤材料的最新研究进展,分析了两种方法制备量子点光纤材料的优缺点,概述了PbSe量子点光纤放大器的研究近况,展望了量子点光纤的应用前景。     

CdSe／HgSe／CdSe量子点量子阱（QDQW）的HREM研究

我们应用胶体化学合成方法制备出具有核壳结构的CdSe/HgSe/CdSe量子点量子阱(QDQW)纳米晶,由于QDQW中载流子的量子限制效应,其光致发光谱(PL)出现了明显的蓝移现象,谱峰也有明显增强。本文中,我们通过对CdSe/HgSe/CdSe量子点量子阱核壳结构进行HREM的研究,并对包裹层这种异质外延生长及PL谱进行分析,获得了有意义的结论。胶体CdSe纳米晶是在水溶液中加以生长[1]。其化学反应式为:Cd2++2OH-+SeSO32-→CdSe+SO32-+H2O(1)通过改变Cd2+、SeSO32-的浓度及溶液中pH值,对CdSe纳米晶的尺度加以控制,并加入化学稳定剂阻止CdSe纳…     

三基色量子点的制备与白光的实现

采用化学溶液方法,以乙基黄原酸盐作为壳层前驱体,制备了红绿蓝三色发光的CdSe/ZnS核壳量子点.以乙基黄原酸锌为前驱体形成ZnS壳层包覆CdSe核量子点,通过调节反应温度与反应气氛等条件获得了发绿光(542nm)及蓝光(483nm)的核壳量子点.以乙基黄原酸镉和乙基黄原酸锌分别作为壳层CdS及ZnS的前驱体制备了发红光(612nm)CdSe/CdS/ZnS核/多壳结构量子点.紫外-可见吸收光谱、荧光光谱及透射电镜研究结果表明,通过条件调节,温度较低时(约230℃)注入乙基黄原酸锌后量子点发光峰出现红移,而温度较高时(约260℃)则发生蓝移.通过不同发光颜色的量子点的混合实现了三基色白光.     

CdSe@CdTe核壳II型量子点掺杂的薄膜太阳能电池

采用胶体化学法制备了CdSe@CdTe核壳量子点,将其置于CdTe量子点层与CdSe量子点层间构筑了三层结构的全无机薄膜太阳能电池(ITO/CdTe/CdSe@CdTe/CdSe/Al),在电池制备过程中对量子点薄膜进行了退火处理。吸收光谱、荧光光谱及荧光寿命测试结果表明所制备的CdSe@CdTe量子点为典型的II型量子点。其光电转换性能测量结果表明所制太阳能电池具有高达0.48%的能量转换效率,这主要得益于三层量子点间能带能量的差异对电子与空穴的定向传输的促进以及退火工艺对薄膜结晶质量的改善。     

In0.4Ga0.6As/GaAs自组织量子点的光伏谱温度特性

自组织生长方法作为一种有效而直接的制备半导体量子点的方法受到重视。本文采用无需在样品上制备电极的电容耦合的光伏谱方法,实验测量了Ｉｎ０．４Ｇａ０．６Ａｓ／ＧａＡｓ自组织量子点在不同的温度下的光伏谱,对测量谱峰进行了指认,研究了量子点谱峰能量位置随温度的依赖关系,实验结果表明,量子点具有与体材料及二维体系不同的温度特性,对实验所测样品,其激子峰能量随温度增加而红移的速率约为ＧａＡｓ体材料带隙变化的１     

II-VI族半导体量子点的发光特性及其应用研究进展

半导体量子点由于具有独特的发光特性而具有极高的应用价值。结合本实验室的工作介绍了半导体量子点的发光原理和发光特性，在实验中发现核壳结构的CdSe／CdS半导体量子点比没有包覆的CdSe半导体量子点的发光稳定性提高．吸收光谱和发射光谱均发生红移，而且粒径不同．半导体量子点所呈现的颜色也不同，随着粒径的增加吸收光谱和发射光谱向长波方向红移。介绍了半导体量子点在光电子器件和生物医学方面的应用．并对其发展前景进行了展望。     

优质量子阱的MBE生长和性能研究

利用国产MBE没备,选择合适的生长参数,获得优质的GaAs/Al_xGa(1-x)As量子阱结构。对共性能和结构参数进行了光荧光测量,荧光峰的形状和温度特性是衡量量子阱质量的重要判据。对n=1的自由激子荧光峰形状进行的讨论和模型分析推得:量子阱界面的平整度达到了单原子层起伏。荧光峰的温度特性表明样品从低温到室温都能保持激子发光特性,量子阱样品的主要性能可与国际水平相媲美。     

量子点的湿法腐蚀制备及尺寸分布研究

介绍了用可见光光刻后用湿法腐蚀制备了ＧａＡｓ／ＡｌＧａＡｓ量子点的方法，并用小光点光荧光的方法检测了所制备量了点的均匀性，从理论上给出了量子点的尺寸分布，并结合多量子阱阱宽的涨落，分析了荧光峰的线型和展宽机制。     

内嵌自组装InAs量子点调制掺杂场效应管的光电特性

研究了阱中生长自组装InAs量子点的光谱特性，获得了室温1.265μm近红外荧光发光，探讨了与量子点尺寸分布相关的发光峰随温度的超常红移现象. 制备了内嵌InAs量子点的异质结调制掺杂场效应晶体管，获得了高耐压的场效应器件电学特性，并有望制成新型红外光电探测场效应管.     

Evidence of thermally activated transfer of excited carriers between CdSe/ZnSe quantum dots

Temperature dependent photoluminescence and cathodoluminescence of selfassembled CdSe/ZnSe quantum dots grown by metalorganic vapor phase deposition were investigated. We found an unusual large red shift and a narrowing of the photoluminescence peak with temperature increases. Cathodoluminescence studies of a small number of quantum dots showed that the broad peak observed in the photoluminescence spectra is, in fact, made up of a series of narrower peaks, coming from quantum dots of different sizes. While the intensity of luminescence from small dots drops monotonously with temperature rises, that from the large dots displays a peculiar behavior. It actually increases within the temperature range of 140–170 K, the same range in which the photoluminescence peak shows narrowing. The simultaneous increase of luminescence from some quantum dots and decrease from others are believed to be responsible for the red shift and narrowing of the observed photoluminescence peak. A simple analytically solvable rate equation model was used to understand the spectral data. We suggest that the unusual behaviors observed can be understood as resulting from a transfer of thermally activated carriers from small to large quantum dots.     

Effect of conjugation with biomolecules on photoluminescence and structural characteristics of CdSe/ZnS quantum dots

The photoluminescence and photoluminescence excitation spectra, the X-ray diffraction patterns, and the effect of conjugation with biomolecules upon these characteristics are studied for silanized CdSe/ZnS quantum dots. Along with the band of annihilating excitons in the quantum dots, the luminescence spectra exhibit emission associated with defects. It is established that the emission spectrum of defects involves at least two components. It is shown that the defects are located mainly at the small-sized quantum dots; the defects responsible for the long-wavelength component are located mainly at the quantum dots larger in size than the quantum dots, at which the defects responsible for the short-wavelength component are located. It is found that conjugation with biomolecules induces not only the blue shift of the excitonic band, but transformation of the emission spectra of defects and an increase in the contribution of defects to the luminescence spectrum as well. The changes observed in the emission spectrum of defects are attributed to the formation of certain emission centers. It is shown that, when conjugated with biomolecules, the quantum dots experience increasing compression strains. This effect is responsible for the blue shift of the luminescence band of the quantum dots.     

Photoluminescence properties of cadmium-selenide quantum dots embedded in a liquid-crystal polymer matrix

The photoluminescence properties of cadmium-selenide (CdSe) quantum dots with an average size of ～3 nm, embedded in a liquid-crystal polymer matrix are studied. It was found that an increase in the quantum-dot concentration results in modification of the intrinsic (exciton) photoluminescence spectrum in the range 500–600 nm and a nonmonotonic change in its intensity. Time-resolved measurements show the biexponential decay of the photoluminescence intensity with various ratios of fast and slow components depending on the quantum-dot concentration. In this case, the characteristic lifetimes of exciton photoluminescence are 5–10 and 35–50 ns for the fast and slow components, respectively, which is much shorter than the times for colloidal CdSe quantum dots of the same size. The observed features of the photoluminescence spectra and kinetics are explained by the effects of light reabsorption, energy transfer from quantum dots to the liquid-crystal polymer matrix, and the effect of the electronic states at the CdSe/(liquid crystal) interface.     

Trapping of charge carriers into InAs/AlAs quantum dots at liquid-helium temperature

The problem of how the probability of trapping of charge carriers into quantum dots via the wetting layer influences the steady-state and time-dependent luminescence of the wetting layer and quantum dots excited via the matrix is analyzed in the context of some simple models. It is shown that the increase in the integrated steady-state luminescence intensity of quantum dots with increasing area fraction occupied by the quantum dots in the structure is indicative of the suppression of trapping of charge carriers from the wetting layer into the quantum dots. The same conclusion follows from the independent decays of the time-dependent luminescence signals from the wetting layer and quantum dots. The processes of trapping of charge carriers into the InAs quantum dots in the AlAs matrix at 5 K are studied experimentally by exploring the steady-state and time-dependent photoluminescence. A series of structures with different densities of quantum dots has been grown by molecular-beam epitaxy on a semi-insulating GaAs (001) substrate. It is found that the integrated photoluminescence intensity of quantum dots almost linearly increases with increasing area occupied with the quantum dots in the structure. It is also found that, after pulsed excitation, the photoluminescence intensity of the wetting layer decays more slowly than the photoluminescence intensity of the quantum dots. According to the analysis, these experimental observations suggest that trapping of excitons from the wetting layer into the InAs/AlAs quantum dots at 5 K is suppressed.     

单分散闪锌矿型CdSe量子点的合成及表征

采用TOPO辅助油相合成的化学方法制备出单分散的CdSe量子点。通过透射电子显微镜、X射线粉末衍射、粒径分布、紫外-可见吸收光谱和光致发光谱等多种测试手段对产物进行了表征,结果表明,CdSe量子点具有闪锌矿型(立方)晶体结构、粒径均匀、尺寸分布窄、发光性能良好的特点。此外,对闪锌矿型CdSe量子点的形成进行了初步分析。     

胶体硒化镉量子点的荧光时间分辨谱研究

使用化学胶体法合成了12个高质量、不同尺寸的胶体硒化镉量子点.测量了样品的时间分辨光致发光谱、TEM谱,同时测量并计算了样品的光致发光量子产率以及光致发光寿命.研究结果表明:硒化镉量子点的光辐射强度与表面相关的光辐射强度均由量子点的表面缺陷形式决定,并且也决定了光致发光量子产率、光致发光寿命.量子点的表面缺陷形式决定于尺寸,在量子点的生长过程中存在的表面的优化/重构也依赖于尺寸.     

Growth of ternary InAlP and InGaP self-assembled quantum dots by metalorganic chemical vapor deposition

We report the characteristics of ternary InAlP and InGaP self-assembled quantum dots grown by metalorganic chemical vapor deposition. The structural and optical properties of these ternary quantum dots are compared with the characteristics of binary InP quantum dots grown under similar conditions. Because these ternary quantum dots have different bandgaps, strain, and composition compared to binary InP quantum dots, the ternary quantum-dot optical and physical properties are markedly different. The quantum-dot structures are grown uncapped (exposed QDs) and capped (embedded QDs) and characterized by atomic force microscopy (AFM) and photoluminescence (PL). InAlP quantum dots have higher densities and smaller sizes and InGaP quantum dots have smaller densities, as compared with InP quantum dots grown under similar conditions. Also, a random and broad size distribution is observed for InGaP quantum dots and the luminescence from InGaP dots is broader than for InP quantum dots.     

Green synthesis of yellow emitting PMMA–CdSe/ZnS quantum dots nanophosphors

We herein report the fabrication of highly fluorescent yellow emitting nanophosphors using CdSe/ZnS quantum dots (QDs) dispersed in polymethyl methacrylate (PMMA). The QDs were synthesised via a simple, non-phosphine and one pot synthetic method in the absence of an inert atmosphere. The as-prepared nanocrystallites were characterised by Fourier transform infrared spectroscopy (FTIR), ultraviolet–visible (UV–vis) and photoluminescence spectroscopy, energy-dispersive spectroscopy (EDS), Raman spectroscopy, transmission electron microscopy (TEM) and high resolution TEM (HRTEM) microscopy. Optical analysis confirmed that the as-synthesised CdSe/ZnS QDs were of high quality with sharp absorption peaks, bright luminescence, narrow emission width and high PL quantum yield (up to 74%). The electron microscope images showed that the QDs are small and spherical in shape with narrow size distributions while the HRTEM micrograph confirmed the high crystallinity of the material. The Raman analysis of the QDs revealed the formation of core–shell structure and the energy dispersive spectroscopy confirmed the presence of the corresponding elements (i.e., Cd, Se, Zn and S). The dispersion of the core–shell QDs in PMMA matrix led to the red-shifting of the emission position from 393 nm in the neat PMMA to 592 nm in the nanocomposite. The fabricated highly fluorescent yellow emitting PMMA–CdSe/ZnS core–shell QDs polymer nanocomposite film display excellent optical properties without loss of luminescence. Furthermore, the as-synthesised organic soluble CdSe/ZnS QDs were successfully converted into highly water soluble QDs after ligand exchange with mercaptoundecanoic acid (MUA) without the loss of their emission properties. The simplicity of the method and the quality of the as-synthesised nanocomposite make it a promising material for the large scale fabrication of diverse optical devices.     

Mn2+‐Doped CdSe Quantum Dots: New Inorganic Materials for Spin‐Electronics and Spin‐Photonics

Recent advances in the chemistry of colloidal semiconductor nanocrystal doping have led to new materials showing fascinating physical properties of potential technological importance. This article provides an overview of efforts to dope one of the most widely studied colloidal semiconductor nanocrystal systems, CdSe quantum dots, with one of the most widely studied transition‐metal dopant ions, Mn²⁺, and describes the major new physical properties that have emerged following successful synthesis of this material. These properties include spin‐polarizable excitonic photoluminescence, magnetic circular dichroism, exciton storage, and excitonic magnetic polaron formation. A brief survey of parallel advances in the characterization of analogous self‐assembled Mn²⁺‐doped quantum dots grown by molecular beam epitaxy is also presented, and the physical properties of the colloidal quantum dots are shown to compare favorably with those of the self‐assembled quantum dots. The rich variety of physical properties displayed by colloidal Mn²⁺‐doped CdSe quantum dots highlights the attractiveness of this material for future fundamental and applied research.     

无机钙钛矿CsPbX3量子点发光材料及器件的研制

全无机钙钛矿量子点是非常具有发展潜力的发光材料,其中CsPbX3(X为C1、Br和I)因其具有非常窄的发光峰、较好的稳定性以及可以在溶液中制备等优点,受到了研究人员的重点关注.文章在室温下根据过饱和析出原理制备了不同卤族元素配比的全无机钙钛矿量子点,该制备方法不需要惰性气氛保护和热注入,量子点的合成可以在几秒内完成.通过光致发光光谱、吸收光谱、X射线衍射等分析方法研究了不同配比CsPbX3量子点的结构特征和光致发光特性.将CsPbX3量子点涂覆在蓝光发光二极管芯片表面实现了器件的白光发射,并分析了其光谱特征.