Decorating Perovskite Quantum Dots in TiO2 Nanotubes Array for Broadband Response Photodetector

Broadband photodetectors based on TiO₂ nanotubes (NTs) array have significant prospects in many fields such as environmental monitoring. Herein, a simple spin‐coating process is successfully adopted to incorporate MAPbI₃ quantum dots (QDs) onto the surface of TiO₂ NTs to form a heterostructure, extending the response range of TiO₂ NT from ultraviolet to visible. Compared with pure TiO₂ NTs, the heterostructure demonstrates an improvement of responsivity in visible range by three orders of magnitude, and maintains its response performance in the UV range simultaneously. The TiO₂ NTs based heterostructure photodetectors demonstrate a relative fast and stable response in the 300–800 nm range and even have a reponsivity of 0.2 A W^?1 at 700 nm. The photoelectric performance of the hybrid photodetector based on TiO₂ NTs maintains well when exposed to moist air for 72 h or heated from room temperature to 100 °C. Moreover, such a TiO₂ NTs/MAPbI₃ QDs heterostructure device demonstrates excellent flexibility and high transparency (85%) in the 400–800 nm range, their photodetecting performance is well retained after 200 cycles of repeated bending at 90°. The present strategy that combines facile electrospinning and solution‐processed QDs may open a new avenue for wide range response and flexible devices construction.     

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.     

半导体量子点集成有机发光二极管的光光转换器进展

介绍的光光转换器是新型红外光-可见光转换器件,红外光产生的光生载流子直接注入有机发光二极管产生可见光。以半导体红外探测与有机发光器件单片集成的光光转换器,直接实现了红外光到可见光的集成转换,在红外凝视技术中有极大的应用潜力。综述了无机红外探测与有机发光的光-光转换器的研究进展。     

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。     

In Situ Electrical Characterization of Anatase TiO2 Quantum Dots

A novel method for performing in situ characterization of the electrical properties of pristine, ultrafine nanopowders is reported. A modified dilatometer, with a spring‐loaded push rod and electrodes, allows for the simultaneous monitoring of the packed nanopowder's lateral displacement as well as its complex impedance spectroscopy as a function of temperature within a controlled environment. Anatase TiO₂ quantum dots of 2 nm diameter, on average, are examined and found to simultaneously shrink and become more resistive upon initial heating. The resistance changes by approximately 3 orders of magnitude upon heating, associated with the desorption of adsorbed water, demonstrating the need for sample preconditioning. Subsequent electrical resistivity measurements, as a function of oxygen partial pressure, over approximately 40 orders of magnitude, at temperatures between 300 °C and 400 °C, exhibit nearly 9 orders of magnitude change in conductivity. The data are consistent with a Frenkel‐based defect disorder model characterized by an enthalpy of reduction of 5.5 ± 0.5 eV.     

Template‐Directed Liquid ALD Growth of TiO2 Nanotube Arrays: Properties and Potential in Photovoltaic Devices

Dense and well‐aligned arrays of TiO₂ nanotubes extending from various substrates are successfully fabricated via a new liquid‐phase atomic layer deposition (LALD) in nanoporous anodic alumina (AAO) templates followed by alumina dissolution. The facile and versatile process circumvents the need for vacuum conditions critical in traditional gas‐phase ALD and yet confers ALD‐like deposition rates of 1.6–2.2 Å cycle^?1, rendering smooth conformal nanotube walls that surpass those achievable by sol–gel and Ti‐anodizing techniques. The nanotube dimensions can be tuned, with most robust structures being 150–400 nm tall, 60–70 nm in diameter with 5–20 nm thick walls. The viability of TiO₂ nanotube arrays deposited on indium tin oxide (ITO)–glass electrodes for application in model hybrid poly(3‐hexylthiophene) (P3HT):TiO₂ solar cells is studied. The results achieved provide platforms and research directions for further advancements.     

Carbon and Graphene Quantum Dots for Optoelectronic and Energy Devices: A Review

As new members of carbon material family, carbon and graphene quantum dots (CDs, GQDs) have attracted tremendous attentions for their potentials for biological, optoelectronic, and energy related applications. Among these applications, bio‐imaging has been intensively studied, but optoelectronic and energy devices are rapidly rising. In this Feature Article, recent exciting progresses on CD‐ and GQD‐based optoelectronic and energy devices, such as light emitting diodes (LEDs), solar cells (SCs), photodetctors (PDs), photocatalysis, batteries, and supercapacitors are highlighted. The recent understanding on their microstructure and optical properties are briefly introduced in the first part. Some important progresses on optoelectronic and energy devices are then addressed as the main part of this Feature Article. Finally, a brief outlook is given, pointing out that CDs and GQDs could play more important roles in communication‐ and energy‐functional devices in the near future.     

一种表面修饰的CdS量子点的合成与特征分析

用无机成核/有机包裹方法成功合成了3～4nm的CdS量子点;用巯基丙三醇(1t鄄hiogly鄄cerol)对CdS量子点进行了表面修饰;对CdS量子点进行了在水溶液中的分散性实验,同时用透     

Role of PbSe Structural Stabilization in Photovoltaic Cells

Semiconductor nanocrystals are promising materials for printed optoelectronic devices, but their high surface areas are susceptible to forming defects that hinder charge carrier transport. Furthermore, correlation of chalcogenide nanocrystal (NC) material properties with solar cell operation is not straightforward due to the disorder often induced into NC films during processing. Here, an improvement in long‐range ordering of PbSe NCs symmetry that results from halide surface passivation is described, and the effects on chemical, optical, and photovoltaic device properties are investigated. Notably, this passivation method leads to a nanometer‐scale rearrangement of PbSe NCs during ligand exchange, improving the long‐range ordering of nanocrystal symmetry entirely with inorganic surface chemistry. Solar cells constructed with a variety of architectures show varying improvement and suggest that triplet formation and ionization, rather than carrier transport, is the limiting factor in singlet fission solar cells. Compared to existing protocols, our synthesis leads to PbSe nanocrystals with surface‐bound chloride ions, reduced sub‐bandgap absorption and robust materials and devices that retain performance characteristics many hours longer than their unpassivated counterparts.     

半导体量子点的器件应用

半导体量子点的生长和性质已成为当今研究的热点。以Ｓ－Ｋ生长模式已成功地生长了无缺陷的半导体量子点。由于其较强的量子效应,量子点结构的光电器件和电子器件有望比量子阱结构的器件具有更好的性能。介绍了量子点在光电器件中的一些应用,包括单电子晶体管、激光器和红外探测器等。     

Efficiency Enhanced Hybrid Solar Cells Using a Blend of Quantum Dots and Nanorods

The cell performance of organic‐inorganic hybrid photovoltaic devices based on CdSe nanocrystals and the semiconducting polymer poly[2,6‐(4,4‐bis(2‐ethylhexyl)‐4H‐cyclopenta[2,1‐b;3,4‐b′]‐dithiophene)‐alt‐4,7‐(2,1,3‐benzothiadiazole)] (PCPDTBT) is strongly dependent on the applied polymer‐to‐nanocrystal loading ratio and the annealing temperature. It is shown here that higher temperatures for the thermal annealing step have a beneficial impact on the nanocrystal phase by forming extended agglomerates necessary for electron percolation to enhance the short‐circuit current. However, there is a concomitant reduction of the open‐circuit voltage, which arises from energy‐level alterations of the organic and the inorganic component. Based on quantum dots and PCPDTBT, we present an optimized organic–inorganic hybrid system utilizing an annealing temperature of 210 °C, which provides a maximum power conversion efficiency of 2.8%. Further improvement is obtained by blending nanocrystals of two different shapes to compose a favorable n‐type network. The blend of spherical quantum dots and elongated nanorods results in a well‐interconnected pathway for electrons within the p‐type polmer matrix, yielding maximum efficiencies of 3.6% under simulated AM 1.5 illumination.     

二氧化硅壳层对CdS:Mn/ZnS量子点的光稳定性影响研究

在量子点表面包覆二氧化硅壳层,能够有效的保护纳米粒子核不受外界环境的影响,使得它在光电子器件和生物标记等领域中有着广泛的应用前景。通过一锅法制备高质量CdS:Mn/ZnS量子点,然后利用反相微乳液方法在量子点的表面继续包覆SiO2层,得到CdS:Mn/ZnS@SiO2多层核壳结构量子点材料。化学性质稳定的ZnS及SiO2材料的包覆使CdS量子点材料的毒副作用降低并有效提高其稳定性,然而CdS:Mn/ZnS量子点的大部分性能在包覆SiO2后都保持不变,因此CdS:Mn/ZnS@SiO2量子点在光学应用中有很大的应用潜力。     

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     

CdS Quantum Dots Encapsulated in Chiral Nematic Mesoporous Silica: New Iridescent and Luminescent Materials

Simultaneous integration of light emission and iridescence into a semiconducting photonic material is attractive for the design of new optical devices. Here, a straightforward, one‐pot approach for liquid crystal self‐assembly of semiconductor quantum dots into cellulose nanocrystal‐templated silica is developed. Through a careful balance of the intermolecular interactions between a lyotropic tetraalkoxysilane/cellulose nanocrystal dispersion and water‐soluble polyacrylic acid/mercaptopropionic acid‐stabilized CdS quantum dots, CdS/silica/nanocellulose composites that retain both chiral nematic order of the cellulose nanocrystals and emission of the quantum dots are successfully co‐assembled. Subsequent removal of the cellulose template and organic stabilizers in the composites by controlled calcination generates new freestanding iridescent, luminescent chiral nematic mesoporous silica‐encapsulated CdS films. The pores of these materials are accessible to analytes and, consequently, the CdS quantum dots undergo strong luminescence quenching when exposed to TNT solutions or vapor.     

有机包裹的Ⅱ-Ⅵ族半导体量子点的制备与表征

介绍了单分散量子点的无机成核/有机包裹的合成方法,并通过选择性沉淀可以得到单分散的半导体量子点;介绍了TEM,XRD,UVV-is吸收谱对纳米Ⅱ-Ⅵ族量子点的表征。     

Multistage Coloring Electrochromic Device Based on TiO2 Nanotube Arrays Modified with WO3 Nanoparticles

WO₃ nanoparticles loaded in TiO₂ nanotube arrays, fabricated by a chemical bath deposition (CBD) technique in combination with a pyrolysis process, is uniform and the diameter can be easily adjusted by the deposition times. The resultant hybrid nanotubes array shows a multistage coloring electrochromic response at different potential bias. The formation of a 3‐dimensional WO₃/TiO₂ junction promotes unidirectional charge transport due to the one‐dimensional features of the tubes, which leads to the significant positive‐shift onset potential of the cathodic reaction (ion insertion) and the highly increased proton storage capacity. Compared to non‐decorated nanotube arrays, the enhanced electrochromic properties of longer lifetime, higher contrast ratio (bleaching time/coloration time), and improved tailored electrochromic behavior could be achieved using the composite films.     

Origins of Low Quantum Efficiencies in Quantum Dot LEDs

The promise for next generation light‐emitting device (LED) technologies is a major driver for research on nanocrystal quantum dots (QDs). The low efficiencies of current QD‐LEDs are often attributed to luminescence quenching of charged QDs through Auger‐processes. Although new QD chemistries successfully suppress Auger recombination, high performance QD‐LEDs with these materials have yet to be demonstrated. Here, QD‐LED performance is shown to be significantly limited by the electric field. Experimental field‐dependent photoluminescence decay studies and tight‐binding simulations are used to show that independent of charging, the electric field can strongly quench the luminescence of QD solids by reducing the electron and hole wavefunction overlap, thereby lowering the radiative recombination rate. Quantifying this effect for a series of CdSe/CdS QD solids reveals a strong dependence on the QD band structure, which enables the outline of clear design strategies for QD materials and device architectures to improve QD‐LED performance.     

Carbon Quantum Dots Codoped with Nitrogen and Lanthanides for Multimodal Imaging

Nanoparticles are increasingly being used as advantageous alternatives to commonly used contrast agents in bioimaging, not only due to their improved imaging capabilities but also their great potential in theranostics. Herein, carbon quantum dots (CQDs) codoped with nitrogen and lanthanides (i.e., Gd and Yb) are synthesized using a one‐pot microwave‐assisted hydrothermal method and evaluated as improved multimodal contrast agents for imaging purposes. The obtained doped‐CQDs exhibit an intense fluorescence emission with excellent quantum yields (66 ± 7%) along with outstanding magnetic resonance (MR) and computed tomography (CT) contrast properties, without showing appreciable cytotoxicity after their exposure to three different cell lines for 24 and 72 h. Such outstanding features turn these nanoparticles into ideal labels for multimodal imaging. To actually prove such potential, first, these CQDs codoped with N and lanthanides are successfully applied to in vitro fluorescence, and MR and CT cell imaging. In addition, such nanoparticles demonstrate to have great potential as contrast agents for multimodal imaging in vivo as significant MR and CT contrast enhancement is observed in the bladder and kidneys of a mouse after their intravenous injection into the tail vein.