喷墨打印镉基绿光量子点发光二极管及其界面

喷墨打印镉基量子点发光二极管(QLEDs)有望应用于大尺寸全彩显示面板且具有材料利用率高的特点而广受关注。但目前喷墨打印器件效率远低于旋涂制备的同结构器件,针对这一问题,本文研究了在PVK空穴传输层上喷墨打印绿光量子点器件及量子点墨水溶剂对传输层界面的影响。研究发现,喷墨打印过程中的层间互溶是影响器件效率的关键,在采用正交溶剂结合喷墨工艺优化实现了高质量的膜层与界面后,获得了6.3%的喷墨印刷绿光QLEDs外量子效率。     

垂直结构多色量子点LED(QD-LED)最新进展

量子点LED以胶体量子点为发光层,通过调节作为发光层量子点的尺寸可以制作出覆盖可见(380-780nm)以及近红外光谱的量子点LED(QD-LED),而且量子点LED器件发出的光谱范围很窄,其光谱半高宽可达30nm。简述了当今国内外关于QD-LED器件结构的研究成果以及器件的制作工艺,介绍了目前课题组最新的一些相关成果。重点阐述了目前已经得到验证的几种量子点器件结构,分析了其存在的优缺点,这些结论对进一步改进QD-LED的结构以及使其可以更有利于商业化提供了参考。     

铯铅卤化物钙钛矿量子点从玻璃中析出的诱导因素

铯铅卤化物(CsPbX_3,X=Cl, Br, I)钙钛矿量子点以其优异的光电性能(如可调的发射光谱、高色纯度和量子效率等)引起了研究者们的广泛关注,但较差的水稳定性、热稳定性和光稳定性等缺点极大地限制了其在光电器件中的应用。目前,提高铯铅卤化物钙钛矿量子点稳定性的一种有效方法是将CsX和PbX_2加入惰性玻璃陶瓷基质中,只要外界提供的能量可以克服成核和晶体生长的能量障碍,玻璃中就会析出铯铅卤化物钙钛矿量子点。本文重点介绍了热处理、激光、应力和水四种铯铅卤化物钙钛矿量子点从玻璃中析出的诱导因素,并分析了每种诱导因素的优缺点,最后提出了每种诱导因素相对适合的玻璃陶瓷和一些建议。     

铯铅卤化物钙钛矿量子点从玻璃中析出的诱导因素EI北大核心CSCD

铯铅卤化物(CsPb X 3,X=Cl,Br,I)钙钛矿量子点以其优异的光电性能(如可调的发射光谱、高色纯度和量子效率等)引起了研究者们的广泛关注,但较差的水稳定性、热稳定性和光稳定性等缺点极大地限制了其在光电器件中的应用。目前,提高铯铅卤化物钙钛矿量子点稳定性的一种有效方法是将Cs X和Pb X 2加入惰性玻璃陶瓷基质中,只要外界提供的能量可以克服成核和晶体生长的能量障碍,玻璃中就会析出铯铅卤化物钙钛矿量子点。本文重点介绍了热处理、激光、应力和水四种铯铅卤化物钙钛矿量子点从玻璃中析出的诱导因素,并分析了每种诱导因素的优缺点,最后提出了每种诱导因素相对适合的玻璃陶瓷和一些建议。     

ZnO作为电子传输层的绿光胶体CdSe量子点LED(QD-LED)的制备与表征

通过调节作为发光层的量子点的尺寸,可以制作出覆盖可见光(380～780 nm)以及近红外光谱的量子点LED(QD-LED),其光谱范围很窄且半高宽可达30 nm。然而量子点LED的寿命、亮度以及效率需要进一步提高才能满足商业化的需求。为了研究QD-LED器件的特性,本文采用523 nm波长的CdSe/ZnS核壳型量子点为发光层、poly-TPD为空穴传输层、ZnO为电子传输层,制备了绿光量子点LED,并表征了器件的特性。     

基于TiO2修饰层的量子点发光二极管设计及其性能

量子点发光二极管(QLEDs)具有色饱和度和色纯度高等优点,在照明与显示领域具有广泛应用前景,成为发光领域研究的热点之一.由于器件采用多层结构,表面和界面问题成为制约QLEDs发展的一个棘手问题.本文使用原子层沉积技术在氧化锌(ZnO)电子传输层和量子点(QDs)发光层之间插入不同厚度的二氧化钛(TiO2)薄层,对Zn...     

半导体量子点和碳点基零维/二维异质结光催化剂构筑及应用

半导体量子点因其具有精准的尺寸调控、独特的光电特性、丰富的表面活性位点等优势,在光催化剂设计和机理研究中获得了广泛关注。与传统半导体量子点主要作为光吸收单元不同,新兴的碳点更是在增加光吸收、促进电荷分离和增加表面反应位点等光催化不同环节均展现出优异的应用潜力。然而,量子点光催化剂由于小尺寸带来电荷复合严重、易团聚、稳定性差等问题而限制了其光催化性能。解决这些问题的主要途径之一是将零维(0D)量子点负载到超薄的二维(2D)纳米片上,形成0D/2D纳米复合材料,使量子点更加分散和稳定,且2D纳米材料促进的加速电荷转移能够抑制光生电荷的复合,从而可以有效地改善量子点基光催化剂的催化活性和稳定性。本文系统阐述了半导体量子点和碳点基0D/2D异质结光催化剂的构筑及应用,着重讨论了不同类型0D/2D异质结的光催化作用机理及面临的挑战,最后对其未来发展进行了分析和展望。     

基于无机电荷产生层的量子点电致发光器件EI北大核心CSCD

利用WO_(3)/ZnO作为电荷产生层(CGL)制备了具有倒置结构的量子点电致发光器件(QLED),相比于传统的基于单层ZnO作为电子传输层的QLED,利用CGL-QLED的电流效率提高了近30%。这主要归因于CGL的电子注入具有电场依赖特性,从而使得器件中的电荷注入更加平衡,提高了激子的形成效率,抑制了载流子导致的猝灭过程。此外,我们通过瞬态电致发光光谱技术及电容特性测试,分析了基于CGL的QLED的器件工作机制,发现CGL中可以存储大量的载流子,从而使得器件在脉冲电压驱动时出现发光过冲现象。其环境稳定性也与常规的基于ZnO的器件一致。而由于CGL独特的电荷产生机制,使得其不依赖于电极功函数特性。我们相信,这种器件结构在改善器件稳定性及良率方面有着巨大潜力。     

高效率钙钛矿量子点发光二极管研究进展

钙钛矿量子点具有光致发光量子产率高、发光光谱可调、光谱宽度窄、缺陷容忍度高以及独特的量子限域效应等优点,因此成为研制新型高效率发光二极管(LED)的热门材料。本文介绍了近几年基于钙钛矿量子点LED的研究最新进展。首先,介绍了钙钛矿量子点独特的晶体结构及钙钛矿发光器件的工作原理。然后,阐述了合成高光致发光量子产率(PLQY)量子点的方法及提高钙钛矿量子点LED效率的若干方法。最后,分析了当前钙钛矿量子点LED所面临的挑战如不稳定性及毒性,以及可应用在显示和照明方面的高效率LED所展现的前景。本综述为研制更高效率以及更加安全的钙钛矿量子点发光器件提供了有益的见解。     

氯化锌修饰蓝光量子点发光二极管EI北大核心CSCD

采用氯化锌(ZnCl_(2))修饰镉基CdSe/ZnS蓝光量子点(B-QD)薄膜,发现与量子点表面结合力更强的ZnCl_(2)能够部分取代量子点长链配体油酸,有效钝化量子点表面缺陷,提高薄膜的荧光量子效率(PLQY)。此外,由于ZnCl_(2)具有偶极作用,使量子点真空能级提高0.2 eV,一方面可改善电子和空穴载流子注入平衡,另一方面可有效降低发光器件的启亮电压,提高器件的发光寿命。这种无机配体修饰量子点薄膜的方法可能为解决蓝光量子点发光二极管(B-QLEDs)因空穴注入困难和量子点表面缺陷导致器件性能不高的问题提供一个有效思路。     

Synthesis and Characterization of CdS/CISe Quantum Dots with Core–Shell Structure

Quantum dots have received great interest due to their excellent optoelectronic properties. However, the surface defects of quantum dots affect the carrier transport and ultimately reduce the photovoltaic efficiency. In this paper, a core–shell quantum dot by hot-injection method is prepared to grow a narrow-band semiconductor layer (CuInSe₂ (CISe) quantumdot) on the surface of a broad-band core material (cadmium sulfide (CdS) nanocrystal). The composition, structure, optical properties, and decay lifetime of CdS/CISe core–shells are investigated in more detail by X-ray diffraction (XRD), transmission electron microscopy (TEM), photoluminescence (PL), UV–vis spectrophotometry, and fluorescence spectroscopy. The CdS/CISe core–shell structure has a broadened absorption range and still shows CISe-related quantum effects. The increased size of the core–shell and the smaller specific surface area of the CISe shell layer lead to a lower carrier complexation chance, which improves the carrier lifetime.     

基于量子点的荧光型太阳能聚光器

近年来,量子点在结构可控、光谱调节和光学稳定方面的研究进展,表明基于量子点的聚光器件表现出优于基于传统有机染料分子的光输出性能。量子点聚光器成为目前量子点研究领域的新方向。量子点在宏量制备和绿色制备方面的深入研究,使得量子点的制造成本逐步降低,基于量子点的聚光器具有光电转换效率和成本上的优势。本文综述了量子点聚光器的研究进展,主要包括荧光型聚光器的优点、聚光器对量子点光学性质的要求、器件制备的工艺和器件的性能表征方法。重点阐述了量子点的太阳光吸收能力、荧光量子产率和重吸收等关键因素对聚光器件性能的影响,同时介绍了该领域目前最新的研究方向,展望了廉价太阳能窗户在未来城镇建筑上的潜在应用。     

量子点液晶显示背光技术

量子点材料兼具极高的色纯度、发光颜色可调以及的荧光量子产率高等特点,已成为显示领域中的明星材料,在提升显示器件的色域方面具有巨大潜力。基于量子点材料的液晶显示背光技术是目前量子点材料在显示器件中的主流应用方向,引起了学术界和工业界的广泛关注。本文将综述量子点液晶显示背光技术的研究进展,主要包括量子点材料的选择、背光结构的应用以及材料复合与封装技术的发展现状,重点介绍了目前产业界广泛关注的量子点光学膜技术,特别是国内自主知识产权的低成本钙钛矿量子点光学膜技术,由于其具备广色域(124%NTSC)、易加工、低成本等特点,已成为具有成长潜力的技术路线。     

High Color-Rendering Index and Stable White Light-Emitting Diodes Based on Highly Luminescent Quantum Dots

Solid-phase color converter-based quantum dots (QDs) white light-emitting diodes (WLEDs) have become promising next-generation solid-state light sources. However, the development of these WLEDs’ production still suffers from constraints involving insufficient color-rendering index (CRI), low color stability, and short operation lifetimes. Here, thick-shell Cd_0.05Zn_0.95S/CdSe/Cd_xZn_1–xS spherical quantum wells are developed with good color tunability from green to red regions and high photoluminescence quantum yield (up to 88% for green wavelengths). QDs with five emission colors are used to fabricate a series of WLEDs, which possess a good correlated color temperature tunability from warm (3210 K) to cool (22 000K) white light, and a high CRI Ra (>90). Specifically, the neutral white light device with Commission Internationale de l´Eclairage (CIE, International Commission on illumination) of (0.36, 0.36) and the standard white light device with CIE of (0.33, 0.33) achieve a CRI Ra up to 95.8 and 95.11, respectively, they also exhibit long operating life and great color stability. These results indicate that the improvement of the performance and stability of the WLED based on thick-shell spherical quantum wells is remarkable progress in the commercialization of QD-based solid-state lighting.     

Ion migration in metal halide perovskite QLEDs and its inhibition

Benefiting from the excellent properties such as high photoluminescence quantum yield (PLQY), wide gamut range, and narrow emission linewidth, as well as low-temperature processability, metal halide perovskite quantum dots (QDs) have attracted wide attention from researchers. Despite tremendous progress has been made during the past several years, the commercialization of perovskite QDs-based LEDs (PeQLEDs) is still plagued by the instability. The ion migration in halide perovskites is recognized as the key factor causing the performance degradation of PeQLEDs. In this review, the elements species of ion migration, the effects of ion migration on device performance and stability, and effective strategies to hinder/mitigate ion migration in PeQLEDs are successively discussed. Finally, the forward insights on the future research are highlighted.     

Efficient Quantum Dot Light-Emitting Diodes Based on Well-Type Thick-Shell CdxZn1−xS/CdSe/CdyZn1−yS Quantum Dots

Device grade quantum dots (QDs) require QDs ensembles to retain their original superior optical properties as in solution. QDs with thick shells are proven effective in suppressing the inter-dot interaction and preserving the emission properties for QDs solids. However, lattice strain–induced defects may form as the shell grows thicker, resulting in a notable photoluminescence quenching. Herein, a well-type Cd_xZn_1−xS/CdSe/Cd_yZn_1−yS QDs is proposed, where ternary alloys CdZnS are adopted to match the lattice parameter of intermediate CdSe by separately adjusting the x and y parameters. The resultant thick-shell Cd_0.5Zn_0.5S/CdSe/Cd_0.73Zn_0.27S QDs reveal nonblinking properties with a high PL QY of 99% in solution and 87% in film. The optimized quantum dot light-emitting diodes (QLEDs) exhibit a luminance of 31547.5 cd m⁻² at the external quantum efficiency maximum of 21.2% under a bias of 4.0 V. The shell thickness shows great impact on the degradation of the devices. The T₅₀ lifetime of the QLEDs with 11.2 nm QDs reaches 251 493 h, which is much higher than that of 6.5 and 8.4 nm QDs counterparts. The performances of the well-type thick-shell QLEDs are comparable to state-of-the-art devices, suggesting that this type of QDs is a promising candidate for efficient optoelectronic devices.     

Transport in graphene nanostructures

Graphene nanostructures are promising candidates for future nanoelectronics and solid-state quantum information technology. In this review we provide an overview of a number of electron transport experiments on etched graphene nanostructures. We briefly revisit the electronic properties and the transport characteristics of bulk, i.e., two-dimensional graphene. The fabrication techniques for making graphene nanostructures such as nanoribbons, single electron transistors and quantum dots, mainly based on a dry etching ??paper-cutting?? technique are discussed in detail. The limitations of the current fabrication technology are discussed when we outline the quantum transport properties of the nanostructured devices. In particular we focus here on transport through graphene nanoribbons and constrictions, single electron transistors as well as on graphene quantum dots including double quantum dots. These quasi-one-dimensional (nanoribbons) and quasi-zero-dimensional (quantum dots) graphene nanostructures show a clear route of how to overcome the gapless nature of graphene allowing the confinement of individual carriers and their control by lateral graphene gates and charge detectors. In particular, we emphasize that graphene quantum dots and double quantum dots are very promising systems for spin-based solid state quantum computation, since they are believed to have exceptionally long spin coherence times due to weak spin-orbit coupling and weak hyperfine interaction in graphene.     

Quantum dots in quantum well structures

Recent progress toward fabricating and characterizing quantum dots in III–V quantum well structures is reviewed. Quantum dots made by use of lithography and etching, including deep-etched, barrier-modulated, strain-induced and interdiffused quantum dots, are described. Quantum dots fabricated by growth, including natural quantum dots, dots on patterned substrates, and self-assembled dots, are discussed. Dot sizes and uniformity, energy-level splittings, and luminescence efficiencies that are now being achieved are discussed. The status of key issues, such as the energy relaxation in quantum dots, is mentioned.     

Fluorinated Boron Nitride Quantum Dots: A New 0D Material for Energy Conversion and Detection of Cellular Metabolism

Quantum dots encompass a broad spectrum of optical, catalytic, and electrochemical properties bringing in novel applications in catalysis, imaging, displays, and optoelectronics. Herein, the unanticipated broad‐spectrum light absorption and high fluorescence quantum yield in fluorinated boron nitride (FBN) quantum dots are discussed. A heterostructure of FBN quantum dots with a wide‐bandgap semiconductor, titania nanotube arrays, exhibits high photocatalytic activity as evidenced by high external quantum efficiency extending from ultraviolet to green region of the solar spectrum (≈24% at 400 nm). The high activity is confirmed using photoelectrochemical hydrogen evolution experiments. Further, it is demonstrated that high fluorescence quantum yield could be tapped for the detection of glycolytic activity in cancer cells compared to normal cells. This finding could shift the paradigm of molecular detection using quantum dots. The 0D structure and the gap states introduced through fluorination are believed to be responsible for these unprecedented characteristics of boron nitride.     

Photochromism and magneto-optic response of ZnO:Mn semiconductor quantum dots fabricated by microemulsion route

ZnO:Mn semiconductor quantum dots were prepared by solution casting led microemulsion route. Quantum dots of average size ∼2 nm were noticed in transmission electron micrographs. The present work highlights colour change phenomena (photochromic effect) of quantum dots while subjected to photon illumination. The magneto-optic measurements e.g. magnetic field (H) vs angle of rotation (θ) show step like behavior and is ascribed to the quantum confinement effect of diluted magnetic ZnO:Mn nanostructures. Further, underlying mechanism responsible for exhibiting photochromism and magneto-optic effects are also discussed.