金属卤化物钙钛矿纳米晶高效发光二极管的制备与器件性能优化

金属卤化物钙钛矿作为一类新型的离子型直接带隙半导体材料在电致发光二极管(LED)中有着重要应用前景. 但实现其应用的前提在于金属卤化物钙钛矿材料需要保持高的发光效率和好的稳定性. 为了提高金属卤化物钙钛矿作为LED发光层的激子结合效率, 从而提升其发光效率, 设计和合成金属卤化物钙钛矿纳米晶材料是一个有效途径. 目前, 基于纳米晶材料设计的金属卤化物钙钛矿LED在绿光和红光(包括近红外光)范围已经展现了高的发光亮度和外量子效率(EQE), 其中最高EQE已经超过了20%, 但其稳定性仍无法满足器件应用的要求. 此外, 更值得关注且更重要的是, 蓝光钙钛矿LED的发光亮度和EQE目前仍然不高. 如何制备高效、 稳定的金属卤化物钙钛矿纳米晶LED, 特别是蓝光LED, 是一个具有重大应用前景且具有挑战性的课题. 本文重点介绍了金属卤化物钙钛矿纳米发光层的结构设计和合成方法及金属卤化物钙钛矿LED的研究进展, 分析了金属卤化物钙钛矿LED不稳定的原因, 并对金属卤化物钙钛矿LED研究面临的挑战和未来发展方向进行了总结与展望.     

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...     

准二维蓝光钙钛矿发光二极管的研究进展

蓝光钙钛矿发光二极管（PeLEDs）是钙钛矿全彩显示和白光照明技术快速发展的核心技术瓶颈。准二维钙钛矿可利用层数调控和量子限域效应实现蓝光发射,还可借助其疏水有机配体显著提升膜层和器件的稳定性,已成为钙钛矿领域的研究热点。本综述总结了准二维蓝光PeLEDs在组分工程、膜层工艺及器件优化方面的进展,分析了准二维蓝光PeLEDs面临的挑战,展望了效率提升途径,并概述了未来研究方向和解决方案。     

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。     

白光LED用荧光粉的研究进展

综述了国内外白光LED用荧光粉的研究进展.根据目前LED实现白光的两种主流方式:蓝光LED芯片+黄色荧光粉(或+绿色/红色荧光粉)和近紫光LED芯片+红/绿/蓝三基色荧光粉,重点介绍了蓝光芯片激发的黄色,绿色和红色荧光粉以及紫光芯片激发的红色,绿色和蓝色荧光粉.文中并给出了部分具有代表性的荧光粉的激发和发射光谱图.归纳了各种基质材料用于荧光粉的优缺点,对该领域存在的问题及其发展趋势作出了分析和展望.     

钙钛矿阵列化组装及其多功能探测器的应用

钙钛矿材料优异的光电性能使其在高集成、 高性能、 多功能光电探测领域具有广泛的应用前景. 近年来, 科研人员致力于钙钛矿阵列化探测器的研究, 并取得了一系列重要的成果. 本文重点评述了钙钛矿材料的阵列化及其多功能探测器的制备和应用, 介绍了钙钛矿材料的结构分类、 阵列化集成方法及光电探测器的基本器件类型和性能指标, 并进一步阐述了基于钙钛矿一维阵列的高性能光电探测器及其多功能探测器的相关应用研究进展. 最后, 对该研究领域未来的发展方向进行了总结和展望.     

4-氟苯乙胺基准二维钙钛矿的合成及其电致发光与激光性能

设计并开发了一种兼具电致发光和光学增益性能的准二维钙钛矿材料。通过向三维钙钛矿CsPbBr₃中引入大体积阳离子4-FPEA⁺(4-氟苯乙胺),利用简易的溶液旋涂法,制备了不同n值量子阱混合分布的准二维钙钛矿薄膜。通过紫外可见吸收光谱和光致发光光谱证明调整4-FPEA⁺的添加量可以对量子阱的分布进行有效调控。结合扫描电子显微镜和原子力显微镜证明4-FPEA⁺的加入可以降低薄膜表面粗糙度。当4-FPEA⁺和CsPbBr₃的物质的量之比为0.6时,薄膜的发光强度最高。将该材料应用在发光二极管(light emitting diodes,LEDs)中,结合冠醚作为添加剂辅助钝化缺陷,实现了外量子效率(EQE)为0.98%的绿光LED器件。在激光性能方面,该材料在室温条件下的最低阈值为17.42μJ·cm^-2,增益系数为35 cm^-1。     

锡钙钛矿太阳能电池的进展与展望

金属卤素钙钛矿是目前最有前景的高效低成本新型太阳能电池材料,但是目前还存在环境友好性和理论效率极限较低的问题。锡钙钛矿环境友好,而且其带隙更窄理论转换效率更高,吸引了广泛的关注。锡钙钛矿太阳能电池(TPSC)近年来发展迅速,是目前效率最高的无铅钙钛矿太阳能电池。本文先介绍了锡钙钛矿的晶体结构、能带结构和光电性质,然后总结了最近在锡钙钛矿领域有代表性的工作和提高光电转化效率的策略,最后讨论了锡钙钛矿发展面临的挑战和未来的发展方向。     

稀土钙钛矿型氧化物双功能催化剂的研究进展EI北大核心CSCD

金属-空气电池具有理论能量密度高、可循环利用以及对环境友好等优点,但其氧还原反应(ORR)和氧析出反应(OER)的动力学缓慢,且依赖于昂贵的贵金属催化剂(例如,Pt或Ir),这都阻碍了其可持续商业化的发展进程。钙钛矿型复合氧化物由于其具有特殊的结构和灵活的可调控性而引起了广泛的关注。本文介绍了水热法与溶剂法、溶胶-凝胶法、静电纺丝法、固相合成法以及聚合物辅助法等含有稀土元素的钙钛矿型双功能催化剂的制备方法,并总结了各制备方法的优缺点。综述了含稀土元素的钙钛矿型双功能催化剂在常见的三种金属-空气电池中的应用研究进展。最后简要阐述了含稀土元素的钙钛矿型电催化剂在结构优化和应用等方面遇到的挑战,并对其未来的发展方向做了展望。     

如何提升铅卤钙钛矿量子点的稳定性?

钙钛矿量子点因其优越的光电性能(如可调节的发光、窄的发光谱线、高的量子效率以及方便制备等)成为半导体发光领域的研究热点之一.虽然钙钛矿量子点在发光二极管方面具有良好的应用前景,但要想实现其商业化,仍然面临着很多问题.首先是稳定性较差,钙钛矿量子点在光、热、空气中会发生不可逆转的降解,进而导致严重的荧光猝灭,这一缺点严重地阻碍了其在实际中的应用.铅卤钙钛矿较差的稳定性也受到了研究者的广泛关注,近年来,许多工作报道了提升钙钛矿量子点稳定性的有效方法.本文详细分析了铅卤钙钛矿量子点不稳定性的来源,包括钙钛矿结构的不稳定性以及环境应力诱导下的降解,总结了近年来关于提升钙钛矿量子点稳定性的基本方法,并提出了改善铅卤钙钛矿量子点稳定性的一些建议.     

Regulating Perovskite Crystallization through Interfacial Engineering Using a Zwitterionic Additive Potassium Sulfamate for Efficient Pure-Blue Light-Emitting Diodes

Quasi-two-dimensional (quasi-2D) perovskites are emerging as efficient emitters in blue perovskite light-emitting diodes (PeLEDs), while the imbalanced crystallization of the halide-mixed system limits further improvements in device performance. The rapid crystallization caused by Cl doping produces massive defects at the interface, leading to aggravated non-radiative recombination. Meanwhile, unmanageable perovskite crystallization is prone to facilitate the formation of nonuniform low-dimensional phases, which results in energy loss during the exciton transfer process. Here, we propose a multifunctional interface engineering for nucleation and phase regulation by incorporating the zwitterionic additive potassium sulfamate into the hole transport layer. By using potassium ions (K⁺) as heterogeneous nucleation seeds, finely controlled growth of interfacial K⁺-guided grains is achieved. The sulfamate ions can simultaneously regulate the phase distribution and passivate defects through coordination interactions with undercoordinated lead atoms. Consequently, such synergistic effect constructs quasi-2D blue perovskite films with smooth energy landscape and reduced trap states, leading to pure-blue PeLEDs with a maximum external quantum efficiency (EQE) of 17.32 %, spectrally stable emission at 478 nm and the prolonged operational lifetime. This work provides a unique guide to comprehensively regulate the halide-mixed blue perovskite crystallization by manipulating the characteristics of grain-growth substrate.     

Sky-blue perovskite light-emitting diodes based on quasi-two-dimensional layered perovskites

A mixed organic(4-phenylbutylamine, 4-PBA) and inorganic(cesium, Cs) cations are used to deposit quasi-two-dimensional layered perovskites. This layered perovskites exhibit good film coverage as twodimensional perovskites and high emission performance close to three-dimensional organic–inorganic hybrid perovskites. Light-emitting diodes(LEDs) are fabricated by using solution process based on the quasi-two-dimensional layered perovskites. The perovskite LEDs exhibit a sky-blue emission with electroluminescence peak at 491 nm and a low turn on voltage at 2.9 V. The maximum external quantum efficiency reaches 0.015% at brightness of 186 cd/m~2.     

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.     

Water-Driven Synthesis of Deep-Blue Perovskite Colloidal Quantum Wells for Electroluminescent Devices

Perovskite colloidal quantum wells (QWs) are promising to realize narrow deep-blue emission, but the poor optical performance and stability suppress their practical application. Here, we creatively propose a water-driven synthesis strategy to obtain size-homogenized and strongly confined deep-blue CsPbBr₃ QWs, corresponding to three monolayers, which emit at the deep-blue wavelength of 456 nm. The water controls the orientation and distribution of the ligands on the surface of the nanocrystals, thus inducing orientated growth through the Ostwald ripening process by phagocytizing unstable nanocrystals to form well-crystallized QWs. These QWs present remarkable stability and high photoluminescence quantum yield of 94 %. Furthermore, we have prepared light-emitting diodes based on the QWs via the all-solution fabrication strategy, achieving an external quantum efficiency of 1 % and luminance of 2946 cd m⁻², demonstrating state-of-the-art brightness for perovskite QW-based LEDs.     

Manipulating Local Lattice Distortion for Spectrally Stable and Efficient Mixed-halide Blue Perovskite LEDs

Mixed-halide perovskites are considered the most straightforward candidate to realize blue perovskite light-emitting diodes (PeLEDs). However, they suffer severe halide migration, leading to spectral instability, which is particularly exaggerated in high chloride alloying perovskites. Here, we demonstrate energy barrier of halide migration can be tuned by manipulating the degree of local lattice distortion (LLD). Enlarging the LLD degree to a suitable level can increase the halide migration energy barrier. We herein report an “A-site” cation engineering to tune the LLD degree to an optimal level. DFT simulation and experimental data confirm that LLD manipulation suppresses the halide migration in perovskites. Conclusively, mixed-halide blue PeLEDs with a champion EQE of 14.2 % at 475 nm have been achieved. Moreover, the devices exhibit excellent operational spectral stability (T₅₀ of 72 min), representing one of the most efficient and stable pure-blue PeLEDs reported yet.     

Self-trapped exciton emission and piezochromism in conventional 3D lead bromide perovskite nanocrystals under high pressure

Developing single-component materials with bright-white emission is required for energy-saving applications. Self-trapped exciton (STE) emission is regarded as a robust way to generate intrinsic white light in halide perovskites. However, STE emission usually occurs in low-dimensional perovskites whereby a lower level of structural connectivity reduces the conductivity. Enabling conventional three-dimensional (3D) perovskites to produce STEs to elicit competitive white emission is challenging. Here, we first achieved STEs-related emission of white light with outstanding chromaticity coordinates of (0.330, 0.325) in typical 3D perovskites, Mn-doped CsPbBr₃ nanocrystals (NCs), through pressure processing. Remarkable piezochromism from red to blue was also realized in compressed Mn-doped CsPbBr₃ NCs. Doping engineering by size-mismatched Mn dopants could give rise to the formation of localized carriers. Hence, high pressure could further induce octahedra distortion to accommodate the STEs, which has never occurred in pure 3D perovskites. Our study not only offers deep insights into the photophysical nature of perovskites, it also provides a promising strategy towards high-quality, stable white-light emission.

We first achieved self-trapped exciton emission with outstanding white-light chromaticity coordinates of (0.330, 0.325) in conventional 3D halide perovskite nanocrystals through pressure engineering.     

Low-Dimensional Phase Regulation to Restrain Non-Radiative Recombination for Sky-Blue Perovskite LEDs with EQE Exceeding 15 %

Achieving efficient blue electroluminescence (EL) remains the fundamental challenge that impedes perovskite light-emitting diodes (PeLEDs) towards commercial applications. The bottleneck accounting for the inefficient blue PeLEDs is broadly attributed to the poor-emissive blue perovskite emitters based on either mixed halide engineering or reduced-dimensional strategy. Herein, we report the high-performing sky-blue PeLEDs (490 nm) with the maximum EQE exceeding 15 % by incorporating a molecular modifier, namely 4,4′-Difluorophenone, for significantly suppressing the non-radiative recombination and tuning of the low-dimensional phase distribution of quasi-2D blue perovskites, which represents a remarkable paradigm for developing the new generation of blue lighting sources.     

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.     

High-Performance Perovskite Light-Emitting Diode with Enhanced Operational Stability Using Lithium Halide Passivation

Defect passivation has been demonstrated to be effective in improving the radiative recombination of charge carriers in perovskites, and consequently, the device performance of the resultant perovskite light-emitting diodes (LEDs). State-of-the-art useful passivation agents in perovskite LEDs are mostly organic chelating molecules that, however, simultaneously sacrifice the charge-transport properties and thermal stability of the resultant perovskite emissive layers, thereby deteriorating performance, and especially the operational stability of the devices. We demonstrate that lithium halides can efficiently passivate the defects generated by halide vacancies and reduce trap state density, thereby suppressing ion migration in perovskite films. Efficient green perovskite LEDs based on all-inorganic CsPbBr₃ perovskite with a peak external quantum efficiency of 16.2 %, as well as a high maximum brightness of 50 270 cd m⁻², are achieved. Moreover, the device shows decent stability even under a brightness of 10⁴ cd m⁻². We highlight the universal applicability of defect passivation using lithium halides, which enabled us to improve the efficiency of blue and red perovskite LEDs.