基于Ⅱ-Ⅵ族半导体量子点的白光LED的研究进展

作为发光可覆盖整个可见光波段的发光材料,Ⅱ-Ⅵ族半导体量子点自上世纪90年代以来一直是构筑白光发光二极管（LED）的关键材料之一。本文主要介绍基于缺陷态发光、单源二色互补发光、三基色复合发光和光致发光等发光原理的半导体量子点的白光LED,并比较了不同类型器件的特点。凭借发光效率等主要性能参数的优势,基于GaN基蓝紫光与量子点荧光粉组合得到的白光LED将最有可能首先实现商业化应用。而在高清显示技术方面,结合微接触印刷技术的三基色复合白光LED具有潜在应用价值。最后简要介绍在提高白光LED发光效率方面的进展。     

峰值波长和浓度对转光膜与白光LED发光性能的影响

本文以高折射率有机硅胶和无机Y3Al5O12:Ce3+发光材料为原料,采用加热固化的方法制备出有机/无机转光膜,系统的研究了发光材料的峰值波长和浓度对于转光膜和制备的白光LED光色性能的研究,并进行了机理分析。研究结果表明：不同峰值波长变量中,545nm对应白光LED最大的光通量,是由于其光谱与人眼明视觉曲线具有最大的重叠面积有关;不同浓度变量中,由于存在发光材料的吸收饱和现象,在9%浓度时白光LED最大的光通量,色温则与浓度变化呈现单向递减趋势,色坐标和光色均匀度则随着浓度的提高而提高,综合多种指标获得本研究中最佳工艺参数为峰值波长为545nm,浓度为9%,对应白光LED器件光通量为131.5lm,色温4551K,色坐标（0.3479,0.3758）,光色位置处于黑体辐射曲线的白光区,说明了转光膜在白光LED领域应用的可行性。     

白光LED灯应用及发展

白光LED灯是LED的新生产品,在多个领域有广大的应用,将会成为主要的发光光源,其未来发展主要分为无机材料LED和有机材料LED(WOLED),尤其是有机材料LED,在化学和材料学上发展的基础上,更是具有高可靠性、高功率性和价格低廉等特点。     

台湾科学家研制出氧化锌白光LED前景光明

台湾的科学家最近以氧化锌（ZnO）／蓝光有机材料复合薄膜,制作出白光发光二极管（LED）。他们利用水热法成功地在蓝光有机发光薄膜上生长无机ZnO纳米柱阵列。此技术有别于传统LED的外延生长制作方式,不仅方法简单且全程低温．对于未来发展白光光源极具吸引力。     

显示技术用稀土有机和稀土无机荧光体研究新进展

主要描述了具有f-f和f-d电子跃迁两类稀土发光材料与它们电子组态相关的发光性能的区别，评述了稀土有机及无机发光材料体系在显示技术中研究的新进展。如在无机体系中，用FED的新型红色CaTiO3:Pr^3 及橙色SnO2:Eu^3 ，用有机体系中新的Eu^3 及Tb^3 配合物分别用于有机EL的红和绿色发光材料，以及含Eu^2 配合物的有机EL特性研究丰富了有机EL技术研究内容。用于白光LED的（Y,Gd)3(Al,Ga)5O12:Ce^3 很引人注目。     

台湾科学家以水热法制造出白光LED

据台湾媒体报道,台湾的科学家最近以氧化锌（ZnO）／蓝光有机材料复合薄膜,制作出白光发光二极管（LED）。他们利用水热法（hydrothermalmethod）,成功地在蓝光有机发光薄膜上成长无机ZnO纳米柱（nanorod）数组。此技术有别于传统LED的外延制作方式,     

零维金属卤化物钙钛矿的A、B、X位对其光物理性质的调控

零维(0D)金属卤化物作为新一代发光材料,因其高效光致发光量子产率(PLQY)和可调节的荧光发射,受到广泛关注。在钙钛矿材料中,通过筛选不同结构类型的钙钛矿,选择合适的离子,对其A、B、X位进行调控,金属卤化物钙钛矿表现出不同的发光特性,其可调节的荧光发射可以覆盖整个可见光区。首先,分别探究了A位为有机或无机阳离子时对0D钙钛矿晶体结构以及光致发光、空气稳定性方面的调控作用;其次,总结了不同B位金属阳离子和掺杂离子对0D钙钛矿结构对称性、发光特性的影响;最后,讨论了0D钙钛矿材料中X位的不同卤素组分和水分子对其光物理性质的调控作用。研究结果表明,相结构的转变所带来的电子结构和光电性能上的差异较为明显,这对开发有前途的卤化物钙钛矿发光材料具有重要的挑战和意义。     

稀土发光材料的发光机理及其应用

稀土是我国的重要战略资源,稀土发光材料在一些方面已得到普遍应用并在新能源和生物医学等方面具有重要的应用前景。该文给出了稀土离子发光材料的基本原理,介绍了含稀土离子发光材料在节能灯、白光半导体发光二极管显示(LED)用荧光粉、等离子显示(PDP)用荧光粉等领域的应用,对在上转换发光、生物荧光标记和下转换提升太阳能效率等方面的应用前景进行了总结和展望。     

新型稀土发光材料

中科院长春光机所白光LED课题组在继研制出蓝光LED转换成白光用新型稀土发光材料之后,开展了紫光LED转换成白光用新型稀土发光材料的研究工作,并成功研制出紫光LED转换成白光用新型稀土发光材料。新型稀土发光材料具有较宽的激发带,激发光谱范围在250～450nm,发光光谱覆盖可见区,范围在430～700nm,由400紫光LED很好匹配,制成的白光LED光通量是紫光LED的20多倍。色坐标:x=0.32=-0.31;y=-0.31=-00.3,色温Te:3000～8000,显色指数大于80,发光效率达到13lm/W。(No.24)新型稀土发光材料…     

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.     

Stable and Bright Pyridine Manganese Halides for Efficient White Light-Emitting Diodes

Highly efficient lead halide perovskites with tunable emission performance have become new candidate materials for light-emitting devices and displays; however, the toxicity of lead and instability of halide perovskites greatly limits their application. Herein, rapid and large-scale synthesis of highly emissive organic–inorganic manganese halide perovskites, (C₅H₆N)₂MnBr₄ and C₅H₆NMnCl₃, are presented by a one-pot solution-based method, of which (C₅H₆N)₂MnBr₄ displays a high absolute photoluminescence quantum yield (95%) in the solid-state. The developed (C₅H₆N)₂MnBr₄ perovskite noticeably exhibits high stability. Therefore both as-synthesized green and red emissive manganese-based phosphors with superior optical properties are used to fabricate blue light pumped white light-emitting diodes (WLEDs), displaying excellent quality white light with a high color rendering index value of 91 and a correlated color temperature of 5331 K. This study not only presents the robust large-scale production synthetic approach for organic–inorganic manganese halide perovskites, but also facilitates the development of high-performance phosphors for future lighting and display technologies.     

可见光通信及其关键技术研究

可见光通信系统采用白光发光二极管(LED)作为光源,因而系统具有通信与照明的双重作用,极大地节约了能源.描述了可见光通信的结构与特点,对可见光通信的一些关键技术做了简单的研究,并介绍了可见光通信的发展动态.     

Highly Efficient Blue‐Emitting Bi‐Doped Cs2SnCl6 Perovskite Variant: Photoluminescence Induced by Impurity Doping

Lead halide perovskites show excellent optoelectronic properties but are unsatisfactory in terms of stability and toxicity. Herein, bismuth (Bi)‐doped lead‐free inorganic perovskites Cs₂SnCl₆:Bi are reported as blue emissive phosphors. Upon Bi doping, the originally nonluminous Cs₂SnCl₆ exhibits a highly efficient deep‐blue emission at 455 nm, with a Stokes shift of 106 nm and a high photoluminescence quantum yield (PLQY) close to 80%. Hybrid density functional theory calculations suggest the preferred formation of [Bi_Sn+V_Cl] defect complex, which is believed to be responsible for the optical absorption and the associated blue emission. The Cs₂SnCl₆:Bi also shows impressive thermal and water stability due to its inorganic nature and the formation of protective BiOCl layer. White light‐emitting diodes (LEDs) are constructed using Cs₂SnCl₆:Bi and commercial yellow phosphors combined with commercial UV LED chips, giving the Commission Internationale de I'Eclairage (CIE) color coordinates of (0.36, 0.37). This work represents a significant step toward the realization of highly efficient, stable, and environmentally benign next‐generation solid‐state lighting.     

Amplified Spontaneous Emission Based on 2D Ruddlesden–Popper Perovskites

2D Ruddlesden–Popper perovskites (RPPs) are a class of quantum‐well (QW) materials, composed of layered perovskite QWs encapsulated between two hydrophobic organic layers. Different from widely investigated 3D‐perovskites with free carriers at room temperature, 2D‐RPPs exhibit strongly bound electron–hole pairs (excitons) for high‐performance solar cells and light emitting diodes (LEDs). Herein, it is reported that self‐organized multiple QWs in 2D‐RPP thin films naturally form an energy cascade, which enables an ultrafast energy transfer process from higher energy‐bandgap QWs to lower energy‐bandgap QWs. Therefore, photoexcitations are concentrated on lower‐bandgap QWs, facilitating the build‐up of population inversion. Room‐temperature amplified spontaneous emission (ASE) from 2D‐RPP thin films is achieved at dramatically low thresholds, with gain coefficients as high as >300 cm^?1, and stoichiometrically tunable ASE wavelengths from visible to near‐infrared spectral range (530–810 nm). In view of the high efficiency reported for LEDs, these solution‐processed 2D‐RPP thin films may hold the key to realize electrically driven lasers.     

Synthesis of 0D Manganese-Based Organic–Inorganic Hybrid Perovskite and Its Application in Lead-Free Red Light-Emitting Diode

Lead-based perovskite light-emitting diodes (PeLEDs) have exhibited excellent purity, high efficiency, and good brightness. In order to develop nontoxic, highly luminescent metal halide perovskite materials, tin, copper, germanium, zinc, bismuth, and other lead-free perovskites have been developed. Here, a novel 0D manganese-based (Mn-based) organic–inorganic hybrid perovskite with the red emission located at 629 nm, high photoluminescence quantum yield of 80%, and millisecond level triplet lifetime is reported. When applied as the emissive layer in the PeLEDs, the maximum recording brightness of devices after optimization is 4700 cd m⁻², and the peak external quantum efficiency is 9.8%. The half-life of the device reaches 5.5 h at 5 V. The performance and stability of Mn-based PeLEDs are one order of magnitude higher than those of other lead-free PeLEDs. This work clearly shows that the Mn-based perovskite will provide another route to fabricate stable and high-performance lead-free PeLEDs.     

Quasi‐2D Inorganic CsPbBr3 Perovskite for Efficient and Stable Light‐Emitting Diodes

Metal halide perovskites are rising as a competitive material for next‐generation light‐emitting diodes (LEDs). However, the development of perovskite LEDs is impeded by their fast carriers diffusion and poor stability in bias condition. Herein, quasi‐2D CsPbBr₃ quantum wells homogeneously surrounded by inorganic crystalline Cs₄PbBr₆ of large bandgap are grown. The centralization of carriers in nanoregion facilitates radiative recombination and brings much enhanced luminescence quantum yield. The external quantum efficiency and luminescence intensity of the LEDs based on this nanocomposite are one order of magnitude higher than the conventional low‐dimensional perovskite. Meanwhile, the use of inorganic nanocomposite materials brings much improved device operation lifetime under constant electrical field.     

高速VLC系统中LED直流偏置对系统误码率的影响

研究了高速可见光通信(VLC)系统中荧光型LED光源的直流偏置电流大小与系统响应时间、误码率的关系;搭建了高速可见光通信测试系统,用于验证如何通过设置合适的LED光源的直流偏置电流使可见光通信系统达到更高的通信速率和更低的误码率.实验测试结果表明,在直流偏置电流为60～80 mA,1W的荧光型LED的响应时间较短,系统的误码率较低,此时可见光通信系统可达到最大传输速率.     

Core/Shell Perovskite Nanocrystals: Synthesis of Highly Efficient and Environmentally Stable FAPbBr3/CsPbBr3 for LED Applications

Lead halide perovskite nanocrystals (PeNCs) are promising materials for applications in optoelectronics. However, their environmental instability remains to be addressed to enable their advancement into industry. Here the development of a novel synthesis method is reported for monodispersed PeNCs coated with all inorganic shell of cesium lead bromide (CsPbBr₃) grown epitaxially on the surface of formamidinium lead bromide (FAPbBr₃) NCs. The formed FAPbBr₃/CsPbBr₃ NCs have photoluminescence in the visible range 460–560 nm with narrow emission linewidth (20 nm) and high optical quantum yield, photoluminescence quantum yield (PLQY) up to 93%. The core/shell perovskites have enhanced optical stability under ambient conditions (70 d) and under ultraviolet radiation (50 h). The enhanced properties are attributed to overgrowth of FAPbBr₃ with all‐inorganic CsPbBr₃ shell, which acts as a protective layer and enables effective passivation of the surface defects. The use of these green‐emitting core/shell FAPbBr₃/CsPbBr₃ NCs is demonstrated in light‐emitting diodes (LEDs) and significant enhancement of their performance is achieved compared to core only FAPbBr₃‐LEDs. The maximum current efficiency observed in core/shell NC LED is 19.75 cd A^‐1 and the external quantum efficiency of 8.1%, which are approximately four times and approximately eight times higher, respectively, compared to core‐only devices.     

Tuning the performance of hybrid organic/inorganic quantum dot light-emitting devices

The luminescence of inorganic core-shell semiconductor nanocrystal quantum dots (QDs) can be tuned across much of the visible spectrum by changing the size of the QDs while preserving a spectral full width at half maximum (FWHM) as narrow as 30 nm and photoluminescence efficiency of 50% [Journal of Physical Chemistry B 101 (46) (1997) 9463] [1]. Organic capping groups, surrounding the QD lumophores, facilitate processing in organic solvents and their incorporation into organic thin film light-emitting device (LED) structures [Nature 370 (6488) (1994) 354] [2]. A recent study has shown that hybrid organic/inorganic QD-LEDs can indeed be fabricated with high brightness and small spectral FWHM, utilizing a phase segregation process which self-assembles CdSe(ZnS) core(shell) QDs onto an organic thin film surface [Nature 420 (6917) (2002) 800] [3]. We now demonstrate that the phase segregation process can be generally applied to the fabrication of QD-LEDs containing a wide range of CdSe particle sizes and ZnS overcoating thicknesses. By varying the QD core diameter from 32 Å to 58 Å, we show that peak electroluminescence is tuned from 540 nm to 635 nm. Increase in the QD shell thickness to 2.5 monolayers (∼0.5 nm) improves the LED external quantum efficiency, consistent with a Förster energy transfer mechanism of generating QD excited states. In this work we also identify the challenges in designing devices with very thin (∼5 nm thick) emissive layers [Chemical Physics Letters 178 (5–6) (1991) 488] [4], emphasizing the increased need for precise exciton confinement. In both QD-LEDs and archetypical all-organic LEDs with thin emissive layers, we show that there is an increase in the exciton recombination region width as the drive current density is increased. Overall, our study demonstrates that integration of QDs into organic LEDs has the potential to enhance the performance of thin film light emitters, and promises to be a rich field of scientific endeavor.     

基于卤化物钙钛矿的法布里-珀罗微腔中激子极化激元（特邀）

当激子与腔光子间的相互作用强于激子和腔光子的衰减时,激子能级与腔模之间产生强耦合,形成的准粒子被称为激子极化激元。激子极化激元有效质量小,同时具有较强的非线性,在慢光和低功耗发光器件等方面具有巨大的应用前景。传统Ⅲ-Ⅴ族无机半导体材料激子束缚能较弱,而有机半导体材料非线性系数较小等问题限制着室温条件下激子极化激元的应用。卤化物钙钛矿材料具有高吸收系数、长扩散长度、高缺陷容忍度以及低非辐射复合率等一系列优异的光电性质,并且具有高的激子束缚能和振子强度,成为研究光与物质强相互作用的理想材料。文中从卤化物钙钛矿结构和法布里-珀罗（Fabry-Pérot, F-P）微腔类型两方面介绍了近年来卤化物钙钛矿与F-P微腔强耦合在激子极化激元方面的研究进展。首先回顾了极化激元的研究背景和卤化物钙钛矿的基本光电特性,其次介绍了三维钙钛矿和二维层状钙钛矿各自的特点以及与F-P微腔强耦合的相关研究,随后对钙钛矿的自构型和非自构型F-P微腔激子极化激元的调控与相关应用进行了讨论,最后总结和展望了卤化物钙钛矿激子极化激元面临的挑战以及未来研究方向。