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.     

Shape‐Controlled Synthesis of Polyhedral Nanocrystals and Their Facet‐Dependent Properties

Growth of inorganic polyhedral nanocrystals with excellent morphology control presents significant synthetic challenges, especially when the development of synthetic schemes to make nanocrystals with systematic shape evolution is desired. Nanocrystals with fine size and shape control facilitate formation of their self‐assembled packing structures and offer opportunities for examination of their facet‐dependent physical and chemical properties. In this Feature Article, recent advances in the synthesis of nanocrystals with systematic shape evolution are highlighted. The reaction conditions used to achieve this morphology change offer insights into the growth mechanisms of nanocrystals. A novel class of polyhedral core–shell heterostructures fabricated using structurally well‐defined nanocrystal cores is also presented. Facet‐dependent photocatalytic activity, molecular adsorption, and catalytic and electrical properties of nanocrystals have been examined and are discussed. Nanomaterials with enhanced properties and functionality may be obtained through continuous efforts in the synthesis of nanocrystals with well‐defined structures and investigation of their plane‐selective properties.     

Mesoporous Colloidal Superparticles of Platinum‐Group Nanocrystals with Surfactant‐Free Surfaces and Enhanced Heterogeneous Catalysis

Synthesis of colloidal superparticles (CSPs) of nanocrystals, a class of assembled nanocrystals in the form of colloidal particles, has been emerging as a new frontier in the field of nanotechnology because of their potential novel properties originated from coupling of individual nanocrystals in CSPs. Here, a facile approach is reported for the controlled synthesis of mesoporous CSPs made of various platinum‐group nanocrystals that exhibit high colloidal stability and ligand‐free surfaces to significantly benefit their applications in solution‐phase heterogeneous catalysis. The synthesis relies on self‐limiting growth of composite particles through coprecipitation of both Pt‐group nanocrystals (or their precursor compounds) and silver halides on sacrificial substrates of colloidal silver particles. The intermediate silver halides in the composite particles play the critical role in limiting the continuous growth (and/or coalescence) of individual Pt‐group nanocrystals and they can be selectively dissolved to create nanoscale pores in the resulting CSPs.     

量子点合成及其光电功能薄膜研究进展

量子点(quantum dots,QDs),也被称为半导体纳米晶体,得益于其廉价的制造成本和独特的光学物理学特性,已经广泛应用于光电探测器和太阳能电池的设计和开发.而量子点的合成则是制备光电探测器和太阳能电池的重要组成部分之一.本文对几种不同的量子点合成技术进行了概述,对国内外不同的基于量子点的光电探测器和太阳能电池进...     

量子点标记及其在植物细胞生物学中的应用

量子点是一种直径在1-100 nm,能接受激发光产生荧光的半导体纳米晶粒,由于其独特的物理、化学特性,在生物学中的应用不断扩大。本文介绍了量子点的合成及功能方面的进展,同时也对其在细胞生物学中的应用进展,特别是对其在植物细胞生物学中的应用进行了评述。此外,对量子点在单分子检测、高分辨率细胞成像及活体动态长时追踪方面的应用前景进行了展望。     

Absorption Properties of Hybrid SnO<Subscript>2</Subscript> Nanocrystal-Carbon Nanotube Structures

Tin oxide (SnO₂) nanocrystals of a few nanometers are of great interest for electronic applications. Here we present a mini-arc plasma method to produce aerosol tin oxide nanocrystals at atmospheric pressure. The product SnO₂ nanocrystals are then assembled onto the external surface of carbon nanotubes (CNTs) to form hybrid SnO₂–CNT structures. The absorption properties of both the SnO₂ nanocrystals and the SnO₂–CNT hybrid structures have been characterized. Quantum size effects have been observed for as-produced SnO₂ nanocrystals. The intrinsic nanoparticle size selection during the assembly process results in a blue shift of the absorption spectrum for hybrid nanostructures.     

Solvothermal Synthesis of High‐Quality All‐Inorganic Cesium Lead Halide Perovskite Nanocrystals: From Nanocube to Ultrathin Nanowire

Recently, all‐inorganic cesium lead halide (CsPbX₃, X = Cl, Br, I) perovskite nanocrystals have drawn much attention because of their outstanding photophysical properties and potential applications. In this work, a simple and efficient solvothermal approach to prepare CsPbX₃ nanocrystals with tunable and bright photoluminescent (PL) properties, controllable composition, and morphology is presented. CsPbX₃ nanocubes are successfully prepared with bright emission high PL quantum yield up to 80% covering the full visible range and narrow emission line widths (from 12 to 36 nm). More importantly, ultrathin CsPbX₃ (X = Cl/Br, Br, and Br/I) nanowires (with diameter as small as ≈2.6 nm) can be prepared in a very high morphological yield (almost 100%). A strong quantum confinement effect is observed in the ultrathin nanowires, in which both the absorption and emission peaks shift to shorter wavelength range compared to their bulk bandgap. The reaction parameters, such as temperature and precursors, are varied to investigate the growth process. A white light‐emitting device prototype device with wide color gamut covering up to 120% of the National Television System Committee standard has been demonstrated by using CsPbBr₃ nanocrystals as the green light source. The method in this study provides a simple and efficient way to prepare high‐quality CsPbX₃ nanocrystals.     

Research progress of low-dimensional perovskites: synthesis, properties and optoelectronic applications

The lead halide-based perovskites, for instance, CH₃NH₃PbX₃ and CsPbX₃ (X=Cl, Br, I), have received a lot of attention. Compared with bulk materials, low-dimensional perovskites have demonstrated a range of unique optical, electrical and mechanical properties, which enable wide applications in solar cells, lasers and other optoelectronic devices. In this paper, we provide a summary of the research progress of the low-dimensional perovskites in recent years, from synthesis methods, basic properties to their optoelectronic applications.     

Semiconductor nanowhiskers: Synthesis,properties, and applications

Recent results of studying the semiconductor’s whisker nanocrystals are reviewed. Physical grounds of growing whisker nanocrystals using the mechanism vapor-liquid-crystal are given and the main epitaxial technologies of synthesis of whisker nanocrystals are described. Thermodynamic and kinetic factors controlling the morphological properties, composition, and crystal structure of whisker nanocrystals are considered in detail. The main theoretical models of the growth and structure of whisker nanocrystals are described. The data on physical properties of whisker nanocrystals and possibilities of their use in nanophotonics, nanoelectronics, and nanobiotechnology are presented.     

Symmetry-Broken Au–Cu Heterostructures and their Tandem Catalysis Process in Electrochemical CO2 Reduction

Symmetry-breaking synthesis of colloidal nanocrystals with desired structures and properties has aroused widespread interest in various fields, but the lack of robust synthetic protocols and the complex growth kinetics limit their practical applications. Herein, a general strategy is developed to synthesize the Au–Cu Janus nanocrystals (JNCs) through the site-selective growth of Cu nanodomains on Au nanocrystals, which is directed by the substantial lattice mismatch between them, with the assistance of judicious manipulation of the growth kinetics. This strategy can work on Au nanocrystals with different architectures for the achievement of diverse asymmetric Au–Cu hybrid nanostructures. Of particular note, the obtained Au nanobipyramids (Au NBPs)-based JNCs facilitate the conversion of CO₂ to C₂ hydrocarbon production during electrocatalysis, with the Faradaic efficiency and maximum partial current density being 4.1-fold and 6.4-fold higher than those of their monometallic Cu counterparts, respectively. The excellent electrocatalytic performances benefit from the special design of the Au–Cu Janus architectures and their tandem catalysis mechanism as well as the high-index facets on Au nanocrystals. This research provides a new approach to synthesize various hybrid Janus nanostructures, facilitating the study of structure-function relationship in the catalytic process and the rational design of efficient heterogeneous electrocatalysts.     

Nonvolatile memory with a metal nanocrystal/nitride heterogeneous floating-gate

Heterogeneous floating-gates consisting of metal nanocrystals and silicon nitride (Si/sub 3/N/sub 4/) for nonvolatile memory applications have been fabricated and characterized. By combining the self-assembled Au nanocrystals and plasma-enhanced chemical vapor deposition (PECVD) nitride layer, the heterogeneous-stack devices can achieve enhanced retention, endurance, and low-voltage program/erase characteristics over single-layer nanocrystals or nitride floating-gate memories. The metal nanocrystals at the lower stack enable the direct tunneling mechanism during program/erase to achieve low-voltage operation and good endurance, while the nitride layer at the upper stack works as an additional charge trap layer to enlarge the memory window and significantly improve the retention time. The write/erase time of the heterogeneous stack is almost the same as that of the single-layer metal nanocrystals. In addition, we could further enhance the memory window by stacking more nanocrystal/nitride heterogeneous layers, as long as the effective oxide thickness from the control gate is still within reasonable ranges to control the short channel effects.     

Organometal Trihalide Perovskites with Intriguing Ferroelectric and Piezoelectric Properties

Organometal trihalide perovskites (OTPs) as a new subclass of perovskite materials have recently aroused increasing interest due to their numerous advantages of facile low‐temperature processing, tunable bandgaps, diverse compositions, and superior charge transfer dynamics, which have been widely used in various applications. In particular, solar cells composed of these perovskites have made unprecedented progress in just a few years with maximum power conversion efficiency, evolving from 3.8 to 21.6%. In spite of such impressive achievement, a fundamental understanding of intrinsic optoelectronic and physiochemical properties is a key challenge impeding the development of the OTPs. This review article aims to provide a concise overview of the current status of OTPs research, highlighting the unique properties of OTPs, especially ferroelectric and piezoelectric properties, which are vital to photovoltaic and piezoelectric applications but still not adequately explained. Various material synthesis strategies of OTPs are surveyed, exhibiting that the OTPs architecture can serve as a promising and robust platform for opening new horizons in ferroelectric and piezoelectric researches. Several applications, including piezoelectric generators, solar cells, light‐emitting diodes, lasers, photodetectors, and water‐splitting cells, demonstrate the latent potentialities of OTPs.     

Highly Controlled Zigzag Perovskite Nanocrystals Enabled by Dipole-Induced Self-Assembly of Nanocubes for Low-Threshold Amplified Spontaneous Emission and Lasing

Self-assembly of nanocrystals into controlled structures while uncompromising their properties is one of the key steps in optoelectronic device fabrication. Herein, zigzag CsPbBr₃ perovskite nanocrystals are demonstrated with a precise number of components with nanocube morphology, these can be successfully obtained through a dipole-induced self-assembly process. The addition of a trace amount of deionized water facilitates the transfer from CsPbBr₃ nanocubes to intermediates of CsPb₂Br₅ and Cs₃In₂Br₉, which then fastly release reaction monomers leading to further homogenous nucleation of CsPbBr₃ nanocubes, followed by the formation of zigzag CsPbBr₃ nanocrystals through a dipole-induced self-assembly process. Dipole moment along <110> axis is found to be the driving force for the assembly of nanocubes into zigzag nanocrystals. The zigzag CsPbBr₃ nanocrystals exhibit desirable optical properties comparable to their nanocube counterparts and offer advantages for amplified spontaneous emission and lasing applications with low pump thresholds of 3.1 and 6.02 µJ cm⁻², respectively. This study not only develops a strategy for producing highly controlled zigzag perovskite nanocrystals and provides insights on the dipole-induced self-assembly mechanisms, but also opens an avenue for their application in lasing.     

Perovskite Single Crystals: Synthesis,Properties, and Applications

Perovskite single crystals have gained enormous attention in recent years due to their facile synthesis and excellent optoelectronic properties including the long carrier diffusion length, high carrier mobility, low trap density, and tunable absorption edge ranging from ultra-violet (UV) to near-infrared (NIR), which offer potential for applications in solar cells, photodetectors (PDs), lasers, etc. In this review, we summarized the synthesis, properties, and applications of organic-inorganic mixed and all-inorganic perovskite single crystals, particularly those through the solution synthesis approach. Challenges towards the crystal growth and stability with future perspectives were also briefly described at the end of this paper.     

PbSe Nanocrystals Produced by Facile Liquid Phase Exfoliation for Efficient UV–Vis Photodetectors

Lead selenide (PbSe)-based nanomaterials have been extensively investigated as building blocks for next-generation optoelectronic devices owing to their unique properties. In this work, PbSe nanocrystals (NCs) have been successfully fabricated by a facile liquid phase exfoliation approach and directly applied as active materials for photo-electrochemical (PEC)-type photodetectors (PDs). Taking advantage of broadband absorption and fast carrier dynamics, the PbSe NCs-based PDs exhibit excellent photo-current density (11.88 μA cm⁻²), photo-responsivity (12.37 mA W⁻¹), response/recovery time (0.12/0.13 s), and long-term cycling stability. The working mechanism of PbSe NCs-based PDs is explored by density functional theory calculations based on their structural and electronic properties under various conditions. It is anticipated that this contribution paves the way to readily fabricate low-dimensional PbSe NCs and extend their practical applications in PEC-type PDs.     

Controlling the Optical Properties of Inorganic Nanoparticles

The sophistication with which we can now prepare and characterize inorganic nanoparticles has inspired new areas of research into the fundamental properties and applications of these fascinating nanoscale systems. In this article some of the recent ideas concerning control of their optical properties are examined and explained, focusing on semiconductor nanocrystals. It is known that the optical properties of nanocrystals can be size‐tunable, but it is less obvious how shape matters. To explain how size as well as shape matters, the electronic structure of nanocrystals is sketched in relatively simple terms, leading to an introduction to deeper concepts at the heart of spectroscopy such as the exciton fine structure. The exciton fine structure states, although obscured by inhomogeneous line broadening, dictate selection rules for optical excitation. These viewpoints are compared and contrasted to well‐established principles in molecular spectroscopy that provide inspiration as well as perspective. The control of optical poperties is founded on our ability to prepare good quality colloidal particles. Recent advances in nanocrystal shape control are described. The current status of heterostructures is examined, with an emphasis on charge separation in CdSe–CdTe nanorods.     

聚合物/纳米半导体电致发光

纳米半导体与聚合物复合形成的新型电致发光材料，在大规模平面显示和移动通信等现代信息显示方面具有广阔的应用前景。在这种复合型电致发光材料体系中，聚合物不仅可用作LED器件的粘接剂，而且在用作无机发光层的分散介质时，对纳米晶粒的表面可以起纯化作用，防止发光猝灭，从而通过控制和调节纳米晶粒的含量和尺寸来调节发光强度和波长。当采用共轭聚合物与纳米半导体形成复合体系时，还可以通过共轭聚合物与纳米半导体间的电子转移来调节发光层的电子结构及其发光性能。利用纳米半导体的高电荷输运性，也可以增强电致发光聚合物发光层的效率。     

Improvement of ITO-free inverted polymer-based solar cells by using colloidal zinc oxide nanocrystals as electron-selective buffer layer

In this study, we report on the improvement of ITO-free inverted polymer/fullerene solar cells by introducing a zinc oxide (ZnO) layer between the active layer and the cathode. The ZnO layers are deposited from solution, using colloidal ZnO nanocrystals with a rodlike shape, which are obtained using a wet-chemical synthesis route at low temperature. The nanocrystals are widely characterized with respect to their structural, optical, and electronic properties. In particular, simulations of powder X-ray diffraction data based on Rietveld refinement are shown to be a suitable method to characterize the average crystallite shape and particle size. Cyclic voltammetry reveals that nanocrystalline ZnO is an appropriate choice as electron-selective buffer layer in organic solar cells based on a bulk heterojunction of poly (3-hexylthiophene) (P3HT) and [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM). Using ITO-free inverted solar cells in substrate configuration with an opaque Cr/Al/Cr bottom electrode, we demonstrate that introducing a cathodic interlayer of ZnO nanocrystals leads to a notable enhancement in photovoltaic performance. The magnitude of the effect is found to depend on the solvents used to process the active layer. In case of absorber blends processed from o-dichlorobenzene, we show an almost threefold increase in efficiency from 0.8 to 2.2% at an active area of 1 cm².     

Investigation of the morphology and electrical characteristics of hybrid blends based on poly(3-hexylthiophene) and colloidal CuInS2 nanocrystals of different shapes

Colloidally synthesized CuInS₂ nanocrystals are a promising candidate for hybrid solar cell applications due to suitable optical and transport properties of copper indium disulfide and being it an eco-friendly material. However, as opposite to solar cells where CuInS₂ is synthesized in situ in a conductive polymer matrix, advances in the field of hybrid solar cells containing colloidal CuInS₂ nanocrystals that are blended after synthesis with a polymer are still negligible. Here, we report about the influence of pyridine, alkylamine, and hexanethiol stabilizing ligands on the morphology of the active layer and the electrical characteristics of solar cells based on elongated and pyramidal CuInS₂ nanocrystals blended with poly(3-hexylthiophene) (P3HT). All CuInS₂ nanocrystals used within this study had a wurtzite crystal structure as revealed by X-ray diffraction. With pyridine as ligand, the morphology was found to depend strongly on the shape of the nanocrystals. Strong agglomeration was observed in the case of elongated nanocrystals and explains the low performance of corresponding solar cells. Employment of hexanethiol as ligand resulted in an improvement of the morphology of the CuInS₂/P3HT layers and enhancement of the rectification ratio of the laboratory solar cells. Nevertheless, it was found that morphology of the active layer is not the main limiting factor in the CuInS₂/P3HT system. According to cyclic voltammetry measurements, unsuitable alignment of the energy levels for CuInS₂ nanocrystals and P3HT was observed. Taking this fact into account, appropriate donor materials for CuInS₂ based bulk heterojunctions are discussed.     

Investigation of LSPR Coupling Effects toward the Rational Design of CsxWO3–δ Based Solar NIR Filtering Coatings

The optical range of localized surface plasmon resonance (LSPR) is extended into the infrared region, thanks to the development of highly doped semiconductor nanocrystals. Particularly, the near-infrared (NIR) range holds a significant interest in managing solar radiation. However, practical applications necessitate the arrangement of particles, which is known to possibly impact their optical properties through LSPR coupling effects. How such coupling modifies the LSPR response in semiconductor hosts remains largely unexplored. In this study, a protocol for producing composite coatings composed of cesium-doped tungsten bronze nanocrystals embedded in a silica matrix is presented. Achieving individual dispersion of nanocrystals is made possible through careful selection of a surface polyglycerol ligand exchange. This allows to tune the interparticle distance by adjusting the nanocrystal volume fraction in the composite. The findings demonstrate that LSPR coupling effects significantly influence the LSPR intensity of nanocrystals in the composite when the nanocrystal-to-nanocrystal distance matches their size. Beyond elucidating the LSPR coupling effect, this study provides insights into the potential use of Cs-HTB nanocrystals for solar control applications. Through the optimization of morphology and film structure, remarkable selectivity is obtained in terms of maintaining good transparency in the visible range while achieving high absorption in the NIR.