蓝光钙钛矿发光二极管:机遇与挑战

金属卤化钙钛矿由于具有优异的光电性能(如:高电子/空穴迁移率,高荧光量子产率,高色纯度,以及光色可调性等),成为应用于发光二极管(LED)的理想材料。近年来,钙钛矿LED的发展十分迅速,红光和绿光钙钛矿LED的外量子效率(EQE)均已超过20%。然而,蓝光(尤其是深蓝光)钙钛矿LED的EQE以及稳定性依然相对落后,这严重制约了钙钛矿LED在高性能、广色域显示领域和高显色指数白光照明领域的应用。因此,总结现阶段蓝光钙钛矿LED的发展,并剖析其机遇与挑战,对未来蓝光甚至整个钙钛矿LED领域的发展至关重要。本文将蓝光钙钛矿LED根据光色细分为天蓝光、纯蓝光、深蓝光三大部分进行总结,回顾了三种LED器件的发展历程,并详细阐述了现阶段实现他们的主要手段以及相关的基础原理,最后分析了它们各自的问题并提出了相应的解决思路。     

通过聚(3,4-乙烯二氧噻吩)-聚苯乙烯磺酸改性实现高性能蓝色钙钛矿发光二极管

金属卤化物钙钛矿材料因其独特的光电特性,在光电器件领域引起了相当大的关注和研究.特别是近年来,绿色和红色钙钛矿发光二极管(PeLEDs)研究取得了显著进展.然而,蓝色PeLEDs的发展落后于绿光和红光PeLEDs,效率也要低得多.其中一个主要原因是空穴传输层与蓝色钙钛矿材料的能级不匹配.在这项研究中,通过使用聚(4-苯乙烯磺酸钠)(PSS-Na)和溴化钾(KBr)改性空穴传输层材料聚(3,4-乙烯二氧噻吩)-聚苯乙烯磺酸(PEDOT:PSS),抑制PEDOT:PSS与钙钛矿材料界面之间的非辐射复合.并通过降低膜的粗糙度来提高钙钛矿膜的质量.结果表明,PSS-Na和KBr有效地提高了空穴传输能力,从而提高了PeLEDs器件的整体性能.通过PSS-Na改性PEDOT:PSS制备的蓝色PeLEDs具有低启亮电压(仅为3.3V)和高外量子效率(EQE)(达到4.12%).随着PEDOT:PSS中进一步加入KBr,蓝色PeLEDs最大EQE达到6.25%,启亮电压降至3 V.此外,与其他蓝光钙钛矿器件相比,该器件在不同电压下也表现出了良好的光谱稳定性.说明通过改性空穴传输层,可以提高钙钛矿发光器...     

手性钙钛矿纳米材料的构筑及光电性能

金属卤化物钙钛矿纳米材料因其丰富的化学结构和优异的光电性能,已成为一种极具应用前景的半导体材料。在钙钛矿无机框架中引入有机手性分子后,能够比较容易地得到手性钙钛矿纳米材料,从而可以极大地推动智能光电材料和自旋电子器件的快速发展。本文将综述手性钙钛矿纳米材料的构筑与手性产生机理的最新研究进展,包括一维手性钙钛矿纳米线、二维及准二维手性有机-无机杂化钙钛矿纳米片、三维手性钙钛矿纳米晶、超分子组装体系中诱导的手性钙钛矿纳米晶等。值得注意的是,不同种类的手性钙钛矿纳米材料在圆二色性、圆偏振发光、铁电性、自旋电子学等方面展现出优异的光电性能及巨大的应用前景。但是,有关手性钙钛矿纳米材料的研究目前还处于初级阶段,其中很多机理还存在争议,许多基础性和应用型的工作也有待开展。     

反溶剂法快速合成高效发光二维锡卤钙钛矿材料

铅卤钙钛矿材料由于其优异的光电性质而受到了广泛关注. 但是, 材料中铅的毒性问题极大地阻碍了其大规模应用. 因此, 寻找与铅卤钙钛矿具有相似光电性质的非铅卤化物钙钛矿材料十分重要. 其中, 锡基卤化物钙钛矿被认为是铅基钙钛矿材料最佳的替代材料之一. 本文通过简便的反溶剂方法, 合成了一系列新型二维(RNH₃)₂SnX₄(R为烷基链, X=Br^-, I^-)钙钛矿材料. 研究结果表明, 所合成的材料具有优异的荧光发射性质, 发光量子效率高达98.5%, 比三维ASnX₃[A=Cs⁺, 甲胺(MA⁺), 甲脒(FA⁺)等]型钙钛矿表现出更好的稳定性. 本文所采用的合成方法简单易行, 有利于实现金属卤化物钙钛矿材料的大规模合成及在固态照明器件和显示器件领域的工业应用.     

金属卤化物钙钛矿光催化的研究进展

太阳能驱动光催化反应降解污染物、制备化学燃料或其他高附加值产品是绿色化学和可再生能源研究的重要方向.近年来,在传统的金属氧化物半导体材料之外,金属卤化物钙钛矿类化合物凭借其优异的光电特性也被逐步应用于高效光催化反应中.这篇文章综述了以铅卤钙钛矿为主的金属卤化物钙钛矿材料近年来在光催化领域的研究进展,总结了金属卤化物钙钛矿材料在光（电）催化产氢、CO₂还原反应和有机物高附加值转化反应中的应用与反应机制及其关键挑战,最后展望了高效稳定的金属卤化物钙钛矿光催化剂的发展方向和前景.     

表面包覆策略:提高全无机铯铅卤钙钛矿纳米晶的稳定性及其在照明显示领域的应用

全无机铯铅卤钙钛矿纳米晶具有荧光量子产率高、色纯度高、色域广等优异的光电性质,在发光二极管、太阳能电池和生物标记等领域具有广阔的应用前景。但由于其离子特性所导致该纳米晶的稳定性较差,严重阻碍了进一步推广应用。尽管已发展出许多提高稳定性的策略,如离子掺杂、表面钝化和表面包覆,但暴露于空气、水和极性溶剂等情况下如何保持钙钛矿纳米晶的稳定性仍然是目前亟待解决的重要问题。此外,钙钛矿纳米晶中的阴离子交换现象也限制了其在多色发光显示领域的应用。通过表面包覆可以有效提高钙钛矿纳米晶的稳定性,同时限制了纳米晶中的阴离子交换,因此近年来成为了科研工作者研究的热点。本文总结了造成钙钛矿纳米晶不稳定的原因,详细介绍了铅卤钙钛矿包覆工艺的研究进展及其在照明显示领域的应用,最后分析了全无机铯铅卤钙钛矿纳米晶发展过程中面临的挑战,并对未来的研究方向进行展望。     

高效率钙钛矿发光二极管的研究进展

钙钛矿发光二极管(LED)由于高的发光色纯度、颜色连续可调、可溶液法制备和材料成本低等优势,被认为是下一代高清柔性显示和平面照明应用最有前景的候选材料之一,受到科学界和产业界的广泛关注。在过去的几年里,钙钛矿LED取得了快速的发展,发光颜色已经实现了从紫外光到近红外光的全覆盖,其中绿光、红光和近红外光的外量子效率均超过了20%。本文首先介绍了钙钛矿LED的基本知识,随后综述了本课题组近年来在高效率钙钛矿LED制备方面取得的研究进展,最后结合领域内的一些代表性工作,分析了领域发展中存在的不足,并对未来产业化应用的前景进行了展望。     

金属纳米团簇的合成及其光致发光性质的调控

金属纳米团簇是一种既具有出色光物理性质,又具有良好生物相容性的零维材料.利用配体对团簇的热力学稳定产物的选择性和还原剂动力学调控可以合成出结构多样的金属纳米团簇,在光学材料、生物医学和催化材料等领域展示出颇具潜力的应用前景.但金属纳米团簇的稳定性差、发光弱等缺点限制了其实际应用,因此通过聚集诱导发光效应和超分子自组装协同调控金属纳米团簇的稳定性及光学性质,可以构筑出结构与发光可控的金属纳米团簇组装体,有效促进金属纳米团簇的实际可用性.本文简要介绍了不同配体保护的金属纳米团簇的合成,阐述了金属纳米团簇的光致发光性质,总结了聚集诱导发光效应对团簇超分子组装体光致发光性质的影响规律,并分析提出了当前研究仍存在的问题及对未来探究的展望.     

基于四齿配体的蓝光d8金属配合物及其OLED应用的研究进展

用于有机发光二极管(OLED)的红光和绿光磷光金属配合物材料在稳定性和发光效率方面均已达到了目前产业化应用的要求,而蓝光磷光配合物则在稳定性方面无法达到应用条件。高能量的激发态以及d-d态引起的配合物分解是造成蓝光磷光OLED器件稳定性差的原因之一。采用四齿配体开发d~8金属配合物是同时提升配合物发光效率和稳定性的途径之一,有望在蓝光磷光材料和器件应用方面取得突破。本文总结了基于四齿配体的蓝光铂(Ⅱ)和钯(Ⅱ)配合物的研究进展,通过探讨配体结构对配合物光物理性质和稳定性的影响,为继续开发具有应用前景的蓝光金属配合物材料提供了指导性方向。     

芴类蓝光生色团在合成有机电致发光材料中的应用

有机电致发光技术在通信、信息、显示和照明等领域显现出巨大的商业应用前景, 十几年来一直是光电信息领域的研究热点之一。相对于无机电致发光材料,有机电致发光材料具有许多优点。芴作为一种具有刚性平面联苯结构的化合物,由于具有宽的能隙、高的发光效率和结构上易于修饰等特点,已成为一类受到各方关注的蓝光生色团。因此,芴类蓝光生色团在合成高效稳定电致蓝光材料、聚芴β相结构的调整、多功能化、主体材料、白光材料、有机激光及有机纳米发光材料等方面得到了广泛的应用。本文从材料合成的角度综述了芴类蓝光生色团在合成有机电致发光材料方面所取得的最新研究进展,讨论了芴类蓝光生色团在上述领域应用过程中所存在的问题和功能拓展方向,并对下一步需要研究的热点问题做了展望。     

Chemical regulation of metal halide perovskite nanomaterials for efficient light-emitting diodes

Metal halide perovskite nanomaterials emerged as attractive emitting materials for light-emitting diodes (LEDs) devices due to their high photoluminescence quantum yield (PLQY), narrow bandwidth, high charge-carrier mobility, bandgap tunability, and facile synthesis. In the past few years, it has been witnessed an unprecedented advance in the field of metal halide perovskite nanomaterials based LEDs (PeLEDs) with a rapid external quantum efficiency (EQE) increase from 0.1% to 14.36%. From the viewpoint of material chemistry, the chemical regulation of metal halide perovskite nanomaterials made a great contribution to the efficiency improvement of PeLEDs. In this review, we categorize the strategies of chemical regulation as A-site cation engineering, B-site ion doping, X-site ion exchange, dimensional confinement, ligand exchange, surface passivation and interface optimization of transport layers for improving the EQEs of PeLEDs. We also show the potentials of chemical regulation strategies to enhance the stability of PeLEDs. Finally, we present insight toward future research directions and an outlook to further improve EQEs and stabilities of PeLEDs aiming to practical applications.     

Using steric hindrance to manipulate and stabilize metal halide perovskites for optoelectronics

The chemical instability of metal halide perovskite materials can be ascribed to their unique properties of softness, in which the chemical bonding between metal halide octahedral frameworks and cations is the weak ionic and hydrogen bonding as in most perovskite structures. Therefore, various strategies have been developed to stabilize the cations and metal halide frameworks, which include incorporating additives, developing two-dimensional perovskites and perovskite nanocrystals, etc. Recently, the important role of utilizing steric hindrance for stabilizing and passivating perovskites has been demonstrated. In this perspective, we summarize the applications of steric hindrance in manipulating and stabilizing perovskites. We will also discuss how steric hindrance influences the fundamental kinetics of perovskite crystallization and film formation processes. The similarities and differences of the steric hindrance between perovskite solar cells and perovskite light emission diodes are also discussed. In all, utilizing steric hindrance is a promising strategy to manipulate and stabilize metal halide perovskites for optoelectronics.

Manipulation on steric hindrance can influence the fundamental kinetics of perovskite crystallization and film formation, therefore stabilizing and passivating perovskite structures, and promoting the commercialization of stable perovskite devices.     

环境友好型无铅卤化物钙钛矿太阳能电池研究进展

ABX_3(A为甲胺、甲脒等有机离子或铯离子,B为铅或锡等金属离子,X为溴、碘等卤化物离子)卤化物钙钛矿材料具有优异的光电特性,是当前太阳能电池研究的前沿和热点之一。然而,这类太阳能电池普遍面临含毒性元素铅和稳定性差等问题,极大地阻碍了钙钛矿太阳能电池商业化应用进程。因此,发展新型高效无铅钙钛矿太阳能电池势在必行。本文评述了环境友好型无铅卤化物钙钛矿太阳能电池的最新研究动态和进展,探讨了该类太阳能电池的制备、性能及其稳定性等问题,展望了其未来发展趋势。     

Organic Matrix Assisted Low-temperature Crystallization of Black Phase Inorganic Perovskites

All-inorganic perovskites have attracted increasing attention for applications in perovskite solar cells (PSCs) and optoelectronics, including light-emitting devices (LEDs). Cesium lead halide perovskites with tunable I/Br ratios and a band gap aligning with the sunlight region are promising candidates for PSCs. Although impressive progress has been made to improve device efficiency from the initial 2.9 % with low phase stability to over 20 % with high stability, there are still questions regarding the perovskite crystal growth mechanism, especially at low temperatures. In this Minireview, we summarize recent developments in using an organic matrix, including the addition and use of organic ions, polymers, and solvent molecules, for the crystallization of black phase inorganic perovskites at temperatures lower than the phase transition point. We also discuss possible mechanisms for this low-temperature crystallization and their effect on the stability of black phase perovskites. We conclude with an outlook and perspective for further fabrication of large-scale inorganic perovskites for optoelectronic applications.     

Recent advances of lead-free metal halide perovskite single crystals and nanocrystals: synthesis,crystal structure,optical properties,and their diverse applications

Lead halide hybrid perovskites have received massive research attention because of their unique inherent photophysical properties that driven them for potential application in the fields of photovoltaics, light-emitting devices, lasing, X-ray detector, and so on. Perovskite single crystals and nanocrystals are generally synthesized via various low-cost solution-processed techniques. The emergence of simple growth approaches of perovskite structures enable to fabricate low-cost and highly efficient devices. However, toxicity of Pb atoms and instability of perovskite structures obstruct further commercialization of these technologies. Recent efforts have been shifted to discover novel, eco-friendly, and stable lead-free metal halide perovskite (LFHP) materials and exploring their different growth processes for various device applications. This review aims to provide an up-to-date analysis of recent progress report on LFHPs and will mainly focus on their growth processes in the single crystalline and nanocrystalline forms. This review also tries to understand how the perovskite crystal structure impacts on their fundamental properties. In addition, we discuss the current progress in various field of applications and their future aspects.     

Bulk Mn2+ Doped 1D Hybrid Lead Halide Perovskite with Highly Efficient,Tunable and Stable Broadband Light Emissions

Mn²⁺ doped colloidal three-dimensional (3D) lead halide perovskite nanocrystal (PNC) has attracted intensive research attention; however, the low exciton binding energy and fatal optical instability of 3D PNC seriously hinder the optoelectronic application. Therefore, it remains significant to explore new stable host perovskite with strongly bound exciton to realize more desirable luminescent property. In this work, we utilized bulk one-dimensional (1D) hybrid perovskite of [AEP]PbBr₅ ⋅ H₂O (AEP=N-aminoethylpiperazine) as structural platform to rationally optimize the luminescent property by a controllable Mn²⁺ doping strategy. Significantly, the series of Mn²⁺-doped 1D [AEP]PbBr₅ ⋅ H₂O show enhanced energy transfer efficiency from the strongly bound excitons of host material to 3d electrons of Mn²⁺ ions, resulting in tunable broadband light emissions from weak yellow to strong red spectral range with highest photoluminescence quantum yield up to 28.41 %. More importantly, these Mn²⁺-doped 1D perovskites display ultrahigh structural and optical stabilities in humid atmosphere, water and high temperature exceeding the conventional 3D PNC. Combined highly efficient, tunable and stable broadband light emissions enable Mn²⁺-doped 1D perovskite as excellent down-converting phosphor showcasing the potential application in white light emitting diode. This work not only provides a profound understanding of low-dimensional perovskites but also opens a new way to rationally design high-performance broadband light emitting perovskites for solid-state lighting and displaying devices.     

Ultrastable Perovskite–Zeolite Composite Enabled by Encapsulation and In Situ Passivation

Metal halide perovskites have been widely applied in optoelectronic fields, but their poor stability hinders their actual applications. A perovskite–zeolite composite was synthesized via in situ growth in air from aluminophosphate AlPO-5 zeolite crystals and perovskite nanocrystals. The zeolite matrix provides quantum confinement for perovskite nanocrystals, achieving efficient green emission, and it passivates the defects of perovskite by H-bonding interaction, which leads to a longer lifetime compared to bulk perovskite film. Furthermore, the AlPO-5 zeolite also acts as a protection shield and enables ultrahigh stability of perovskite nanocrystals under 150 °C heat stress, under a 15-month long-term ambient exposure, and even in water for more than 2 weeks, respectively. The strategy of in situ passivation and encapsulation for the perovskite@AlPO-5 composite was amenable to a range of perovskites, from MA- to Cs-based perovskites. Benefiting from high stability and photoluminescence performance, the composite exhibits great potential to be virtually applied in light-emitting diodes (LEDs) and backlight displays.