Trade-Off Between Efficiency and Stability of CsPbBr3 Perovskite Quantum Dot-Based Light-Emitting Diodes by Optimized Passivation Ligands for Br/Pb

Although significant progress has been made in improving the external quantum efficiencies (EQEs) of perovskite quantum dot (QD) light-emitting diodes (QLEDs), understanding the degradation mechanism and enhancing stability remain a challenge. Herein,  increasing the content of Br-based passivation ligands is shown to enhance the EQE up to 16.1% by reducing the defects of CsPbBr₃ QDs in a Br-rich environment. However, the operational lifetimes of perovskite QLEDs gradually decrease with the increase of halide content, owing to the intensified ion migration under continuous electric field confirmed by the current behavior of QLEDs and time-of-flight secondary-ion mass spectrometry. Furthermore, a thorough analysis of the relationship between electricity and luminance of QLEDs suggests that a small amount of residue oleic acid ligands could weaken ion migration. Accordingly, a halide- and acid-hybrid (HAH) co-passivation strategy is proposed to optimize the content of Br- and acid-based ligands, and achieve a maximum EQE of 18.6% and an operational lifetime (T₅₀, extrapolated) of 213 h for CsPbBr₃ QLEDs. This approach for passivating QDs combines the high efficiency of Br-based ligands with the improved stability of acid-based ligands. The study elucidates the correlation between ligands and device performance, highlighting the significance of two or even multiple ligands for efficient and stable perovskite QLEDs.     

Laser-Printed Plasmonic Metasurface Supporting Bound States in the Continuum Enhances and Shapes Infrared Spontaneous Emission of Coupled HgTe Quantum Dots

In order to advance the development of quantum emitter-based devices, it is essential to enhance light-matter interactions through coupling between semiconductor quantum dots with high quality factor resonators. Here, efficient tuning of the emission properties of HgTe quantum dots in the infrared spectral region is demonstrated by coupling them to a plasmonic metasurface that supports bound states in the continuum. The plasmonic metasurface, composed of an array of gold nanobumps, is fabricated using single-step direct laser printing, opening up new opportunities for creating exclusive 3D plasmonic nanostructures and advanced photonic devices in the infrared region. A 12-fold enhancement of the photoluminescence in the 900–1700 nm range is observed under optimal coupling conditions. By tuning the geometry of the plasmonic arrays, controllable shaping of the emission spectra is achieved, selectively enhancing specific wavelength ranges across the emission spectrum. The observed enhancement and shaping of the emission are attributed to the Purcell effect, as corroborated by systematic measurements of radiative lifetimes and optical simulations based on the numerical solution of Maxwell's equations. Moreover, coupling of the HgTe photoluminescence to high quality factor modes of the metasurface improves emission directivity, concentrating output within an ≈20° angle.     

Calibration-Free and High-Sensitivity Microwave Detectors Based on InAs/InP Nanowire Double Quantum Dots

At the cutting-edge of microwave detection technology, novel approaches which exploit the interaction between microwaves and quantum devices are rising. In this study, microwaves are efficiently detected exploiting the unique transport features of InAs/InP nanowire double quantum dot-based devices, suitably configured to allow the precise and calibration-free measurement of the local field. Prototypical nanoscale detectors are operated both at zero and finite source-drain bias, addressing and rationalizing the microwave impact on the charge stability diagram. The detector performance is addressed by measuring its responsivity, quantum efficiency and noise equivalent power that, upon impedance matching optimization, are estimated to reach values up to ≈2000 A W⁻¹, 0.04 and ≈${10}^{-16}\mathrm{W}/\sqrt{Hz}$, respectively. The interaction mechanism between the microwave field and the quantum confined energy levels of the double quantum dots is unveiled and it is shown that these semiconductor nanostructures allow the direct assessment of the local intensity of the microwave field without the need for any calibration tool. Thus, the reported nanoscale devices based on III-V nanowire heterostructures represent a novel class of calibration-free and highly sensitive probes of microwave radiation, with nanometer-scale spatial resolution, that may foster the development of novel high-performance microwave circuitries.     

One-Step Polymeric Melt Encapsulation Method to Prepare CsPbBr3 Perovskite Quantum Dots/Polymethyl Methacrylate Composite with High Performance

All-inorganic CsPbBr₃ perovskite quantum dots (PQDs) exhibit excellent photoelectric properties and application prospects in the field of light-emitting diodes (LEDs) and display devices. However, these possess poor long-term stability to UV irradiation, water, heat, and oxygen. Using polymethyl methacrylate (PMMA) as the matrix along with CH₃(CH₂)₁₆COOCs, [CH₃(CH₂)₁₆COO]₂Pb, and KBr as the perovskite sources, CsPbBr₃ PQDs/PMMA composites are for the first time prepared via an in situ polymeric melt encapsulation method. Special attention is paid to the effects of synthesis conditions on the photoluminescent quantum yield (PLQY) of the composites. The optimized CsPbBr₃ PQDs/PMMA composite reveals excellent performance with ≈82.7% PLQY and ≈18.6 nm full width at a half-maximum (FWHM). In particular, after 90 h of UV irradiation or 35 days of heating at 60 °C, the luminous intensity remains almost unchanged. In addition, after soaking in water for 15 days, it retains up to ≈53% of the initial luminous intensity, meaning that the composite possesses long-term stability to UV irradiation, heat, and water. The as-prepared white LED (WLED) based on the composite evidences the wide color gamut (126.5% National Television System Committee (NTSC)) and a luminous efficiency of 32 lm W⁻¹. This work offers a novel, easily industrialized one-step, and solvent free route for low-temperature synthesis of all-inorganic PQDs with broad application prospects.     

Sustainable and Self‐Enhanced Electrochemiluminescent Ternary Suprastructures Derived from CsPbBr3 Perovskite Quantum Dots

Lead halide perovskite quantum dots (QDs) are promising electrochemiluminescence (ECL) nanoemitters due to their fascinating photophysical properties. However, due to their poor structural stability against the external environment, the trade‐off between their colloidal stability and carrier injection/transport efficiency is a major challenge in the advancement of perovskite‐based ECL technology. In this work, intense and stable ECL from CsPbBr₃ (CPB) QDs is achieved by simultaneously encapsulating CPB QDs and coreactant (CoR) into in situ generated SiO₂ matrix via hydrolysis of tetramethyl orthosilicate. The well‐designed architecture of the as‐obtained CPB‐CoR@SiO₂ nanocomposites (NCs) guarantees not only greatly improved stability thanks to the peripheral SiO₂ protecting matrix, but also efficient self‐enhanced ECL between CPB and the intra‐coreactants. Consequently, by elaborately selecting the CoR molecules with different tertiary/secondary amines and functional groups, multifold higher (up to 10.2 times) ECL efficiencies are obtained for the CPB‐CoR@SiO₂ NCs alone in reference to the standard Ru(bpy)₃²⁺/tri‐n‐propylamine system. This work provides an efficient design strategy for obtaining stable and highly efficient ECL from perovskite QDs, and offers a new perspective for the development and application of perovskite‐based ECL system.     

CsPbBr3@Glass Nanocomposite with Green-Emitting External Quantum Efficiency of 75% for Backlit Display

Robust amorphous glass protected CsPbBr₃ (CsPbBr₃@glass) perovskite quantum dots (PeQDs) with ultra-pure green emission and superior long-term stability are highly desirable for developing wide-color-gamut liquid crystal displays. However, most of the reported CsPbBr₃@glass nanocomposites are subject to low external quantum efficiency (EQE). This work demonstrates that ZrO₂ additive has an “accumulation” effect on the borosilicate glass network structure to promote in situ nucleation/growth of PeQDs inside glass rather than self-crystallization. This effect is beneficial in reducing surface defects, improving the quality of PeQDs, and thus boosting radiative recombination of excitons. As a consequence, the as-prepared CsPbBr₃@glass shows a record EQE of up to 75% and can pass the accelerated aging tests at 85 °C/85% RH for 1000 h and blue light irradiation over 2000 h. Finally, a prototype display using CsPbBr₃@glass-based straight-down backlit unit is designed and gains more favorable responses in blind selection tests for its high brightness of 2647 cd m⁻² and high color purity of 88%. The findings will pave the way for realizing the commercial application of CsPbBr₃@glass nanocomposite in PeQDs-converted backlit display.     

Self‐Powered UV–Vis–NIR Photodetector Based on Conjugated‐Polymer/CsPbBr3 Nanowire Array

Perovskite photodetectors have attracted intensive research interest due to promising applications in sensing, communication, and imaging. However, their performance is restricted by the narrow spectrum range, required power source, and instability in ambient environment. To address these issues, a self‐powered photodetector based on the inorganic CsPbBr₃ perovskite nanowire array/conjugated‐polymer hybrid structure is designed. The spectra response range of the device can be extended to 950 nm, along with outstanding stability, fast response speed (111/306 µs), and large detectivity (1.2 × 10¹³ Jones). The performance parameters are comparable to or even better than most reported CsPbBr₃ and conjugated‐polymer photodetectors. The excellent performance is mainly attributed to the efficient carrier generation, separation, and transport resulting from array structure and favorable band structure.     

渐逝波耦合半导体量子点光纤放大器

基于半导体量子点的特性,结合光纤渐逝波耦合器,提出了一种新型的光纤放大器件,它将以溶液形式的硫化铅(PbS)半导体量子点材料沉积于耦合器熔锥区,信号光和抽运光通过渐逝波共同与半导体量子点材料相互作用,实现光的放大作用。PbS量子点材料是采用工艺容易控制的反胶束法制备的,通过透射电镜(TEM)测量得到其粒子尺寸小于10 nm。利用工作波长为980 nm,功率为30 mW的半导体激光器抽运光源对该光纤放大器抽运,在1310 nm波段得到了大于4 dB的增益,这是半导体量子点尺寸效应引起的光谱蓝移现象的体现。因此,这种有源区短、器件结构紧凑的光纤放大器在高速、宽带光纤接入等领域具有重要的实际意义和应用价值。     

Enhanced Photoluminescence and Photoresponsiveness of Eu3+ Ions-Doped CsPbCl3 Perovskite Quantum Dots under High Pressure

Metal halide perovskite quantum dots (QDs) have garnered tremendous attention in optoelectronic devices owing to their excellent optical and electrical properties. However, these perovskite QDs are plagued by pressure-induced photoluminescence (PL) quenching, which greatly restricts their potential applications. Herein, the unique optical and electrical properties of Eu³⁺-doped CsPbCl₃ QDs under high pressure are reported. Intriguingly, the PL of Eu³⁺ ions displays an enhancement with pressure up to 10.1 GPa and still preserves a relatively high intensity at 22 GPa. The optical and structural analysis indicates that the sample experiences an isostructural phase transition at approximately 1.53 GPa, followed by an amorphous state evolution, which is simulated and confirmed through density functional theory calculations. The pressure-induced PL enhancement of Eu³⁺ ions can be associated with the enhanced energy transfer rate from excitonic state to Eu³⁺ ions. The photoelectric performance is enhanced by compression and can be preserved upon the release of pressure, which is attributed to the decreased defect density and increased carrier mobility induced by the high pressure. This work enriches the understanding of the high-pressure behavior of rare-earth-doped luminescent materials and proves that high pressure technique is a promising way to design and realize superior optoelectronic materials.     

Ultrafast Responsive and Low-Energy-Consumption Poly(3-hexylthiophene)/Perovskite Quantum Dots Composite Film-Based Photonic Synapse

Emulation of photonic synapses through photo-recordable devices has aroused tremendous discussion owing to the low energy consumption, high parallel, and fault-tolerance in artificial neuromorphic networks. Nonvolatile flash-type photomemory with short photo-programming time, long-term storage, and linear plasticity becomes the most promising candidate. Nevertheless, the systematic studies of mechanism behind the charge transfer process in photomemory are limited. Herein, the physical properties of APbBr₃ perovskite quantum dots (PQDs) on the photoresponsive characteristics of derived poly(3-hexylthiophene-2,5-diyl) (P3HT)/PQDs-based photomemory t hrough facile A-site substitution approach are explored. Benefitting from the lowest valance band maximum and longest exciton lifetime of FAPbBr₃ quantum dot (FA-QDs), P3HT/FA-QDs-derived photomemory not only exhibits shortest photoresponsive characteristic time compared to FA_0.5Cs_0.5PbBr₃ quantum dots (Mix-QDs) and CsPbBr₃ quantum dots (Cs-QDs) but also displays excellent ON/OFF current ratio of 2.2 upon an extremely short illumination duration of 1 ms. Moreover, the device not only achieves linear plasticity of synapses by optical potentiation and electric depression, but also successfully emulates the features of photon synaptic such as pair-pulse facilitation, long-term plasticity, and multiple spike-dependent plasticity and exhibits extremely low energy consumption of 3 × 10⁻¹⁷ J per synaptic event.     

Surface Modification Strategy Synthesized CsPbX3 Perovskite Quantum Dots with Excellent Stability and Optical Properties in Water

The poor stability of CsPbX₃ (X = Cl, Br, I) perovskite quantum dots (PQDs) in polar solvents such as water, seriously hinders their practical application. Herein, 5-Bromovaleric acid (BVA) is used to replace oleic acid (OA), the most common surface ligand in CsPbX₃ PQDs synthesis. Under the synergic action of oleylamine (OLA), CsPbX₃ PQDs with high water stability can be synthesized directly in water. Because the carboxyl ligands provided by BVA, and the long chain amines provided by OLA formed hydrophobic shells on the surface of CsPbBr₃ PQDs, the obtained CsPbBr₃ PQDs still has high luminescence intensity and photoluminescence quantum yield after being dispersed in water for several days, and the luminescence peak is always maintained at 518 nm. In contrast, the luminescence intensity of CsPbBr₃ PQDs synthesized with OA and OLA is <1% of the initial intensity after only 30 min. CsPbCl₃ and CsPbI₃ PQDs synthesized directly in water by this method also show high water stability. In this study, for the first time the synthesis method of CsPbX₃ PQDs with high water stability using BVA/OLA as surface ligands is proposed, which provides an effective way to explore the synthesis of PQDs that can maintain stability in water.     

室温合成的钙钛矿量子点及其电致发光二极管

采用室温合成法制备出CsPbBr3钙钛矿量子点,并采用乙酸乙酯对量子点进行了一次、二次和三次清洗,以控制其表面配体密度。然后,利用合成并经过清洗的钙钛矿量子点制备了结构为ITO/PEDOT∶PSS/PTAA/CsPbBr3 QD/TPBi/LiF/Al的电致发光二极管(QLED)。研究了经不同清洗次数的量子点材料制备的器件的光电性能。结果表明,清洗2次的量子点在电荷注入与溶液稳定性之间得到平衡,利用其制备的钙钛矿QLED获得了最大亮度为1405cd/m²、外量子效率为0.6%、色坐标为(0.127,0.559)的绿光发射。     

Passivating {100} Facets of PbS Colloidal Quantum Dots via Perovskite Bridges for Sensitive and Stable Infrared Photodiodes

Solution-processed PbS colloidal quantum dots (CQDs) are promising optoelectronic materials for next-generation infrared imagers due to their monolithic integratability with silicon readout circuit and tunable bandgap controlled by CQDs size. However, large-size PbS CQDs (diameter >4 nm) for longer shortwave-infrared photodetection consist mainly of {100} facets with incomplete surface passivation and unsatisfied stability. Here, it is reported that perovskite-bridged PbS CQDs, in which the {100} facets of the CQDs are epitaxially bridged with CsPbI_3–xBr_x perovskite, can achieve improved passivation and enhanced stability in comparison with the traditional strategies. The resultant infrared CQDs photodiodes exhibit significantly reduced dark current, nearly 50% enhanced photoresponse, and improved work stability. These superior properties synergistically produce the most balanced performance (with a high −3 dB bandwidth of 42 kHz and an impressive specific detectivity of 6.2 × 10¹² Jones) among the reported CQDs photodetectors.     

Facile Synthesis of Graphene Quantum Dots from 3D Graphene and their Application for Fe3+ Sensing

Owing to their small size, biocompatibility, unique and tunable photoluminescence, and physicochemical properties, graphene quantum dots (GQDs) are an emerging class of zero‐dimensional materials promising a wide spectrum of novel applications in bio‐imaging, optical, and electrochemical sensors, energy devices, and so forth. Their widespread use, however, is largely limited by the current lack of high yield synthesis methods of high‐quality GQDs. In this contribution, a facile method to electrochemically exfoliate GQDs from three‐dimensional graphene grown by chemical vapor deposition (CVD) is reported. Furthermore, the use of such GQDs for sensitive and specific detection of ferric ions is demonstrated.     

Design and Synthesis of Fluorinated Quantum Dots for Efficient and Stable 0D/3D Perovskite Solar Cells

Dimensionality engineering involving the low-dimensional and 3D perovskites has been demonstrated as an efficient promising strategy to modulate interfacial energy loss as well as instability in perovskite solar cells (PSCs). Herein, the use of fluorinated Cesium Lead Iodide (CsPbI₃) perovskite quantum dot (PQD) is first reported as interface modification layer for PSCs. The binding between the CsPbI₃ PQD surface and native oleic acid (OLA)/oleylamine (OAm) ligands is governed by a dynamic adsorption–desorption equilibrium. Perfluorooctanoic acid (PFA) with stronger binding affinity and more hydrophobic nature is explored to partially replace OLA to prepare the fluorinated ligand capped CsPbI₃ PQDs (F-CsPbI₃). Through optimization of the addition of PFA during hot-injection synthesis, the in situ treated F-CsPbI₃ PQDs display reduced surface defect states, higher photoluminescence quantum yields together with improved stability. Subsequently, both CsPbI₃ and F-CsPbI₃ PQDs are utilized as interface engineering layer in PSCs, delivering the best efficiency values of 21.99% and 23.42%, respectively, which is significantly enhanced compared to the control device (20.37%). More importantly, benefiting from its more hydrophobic properties, the F-CsPbI₃ PQD treated device exhibits excellent ambient storage stability (25 °C, relative humidity: 35–45%), retaining over 80% of its initial efficiency after 1500 h aging.     

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.     

Enhancing Resistive Switching Performance and Ambient Stability of Hybrid Perovskite Single Crystals via Embedding Colloidal Quantum Dots

Hybrid organic‐inorganic halide perovskites are actively pursued for optoelectronic technologies, but the poor stability is the Achilles’ heel of these materials that hinders their applications. Very recently, it has been shown that lead sulfide (PbS) quantum dots (QDs) can form epitaxial interfaces with the perovskite matrix and enhance the overall stability. In this work, it is demonstrated that embedding QDs can significantly modify the transport property of pristine perovskite single crystals, endowing them with new functionalities besides being structurally robust and free from grain boundaries. Resistive switching memory devices are constructed using solution‐processed CH₃NH₃PbBr₃ (MAPbBr₃) perovskite single crystals and the QD‐embedded counterparts. It is found that QDs could significantly enhance the charge transport and reduce the current–voltage hysteresis. The pristine singe crystal device exhibits negative differential resistance, while the QD‐embedded crystals are featured with filament‐type switching behavior and much improved device stability. This study underscores the potential of QD‐embedded hybrid perovskites as a new media for advanced electronic devices.     

Plasmonic Nanowire‐Enhanced Upconversion Luminescence for Anticounterfeit Devices

A novel, efficient, cost‐effective, and high‐level security performance anticounterfeit device achieved by plasmonic‐enhanced upconversion luminescence (UCL) is demonstrated. The plasmonic architecture consists of the randomly dispersed Ag nanowires (AgNWs) network, upconversion nanoparticles (UCNPs) monolayer, and metal film, in which the UCL is enhanced by a few tens, compared to reference sample, becuase the plasmonic modes lead to the concentration of the incident near infrared (NIR) light in the UCNPs monolayer. In the configuration, both the localized surface plasmons (LSPs) around the metallic nanostructures and gap plasmon polaritons (GPPs) confined in the UCNPs monolayer, significantly contribute to the UCL enhancement. The UCL enhancement mechanism resulting from enhanced NIR absorption, boosted internal quantum process, and formation of strong plasmonic hot spots in the plasmonic architecture is analyzed theoretically and numerically. More interestingly, a proof‐of‐concept anticounterfeit device using the plasmonic‐enhanced UCL is proposed, through which a nonreusable and high‐level cost‐effective security device protecting the genuine products is realized.     

耦合GaN/AlxGa1-xN量子点的非线性光学性质

在有效质量和偶极矩近似下,考虑了由于压电极化和自发极化所引起的内建电场和量子点的三维约束效应,对纤锌矿对称Al_xGa_(1-x)N/GaN/Al_xGa_(1-x)N/GaN/Al_xGa_(1-x)N圆柱型应变耦合量子点中激子非线性光学性质进行了研究。计算结果表明,内建电场使吸收光谱向低能方向移动,发生红移现象,并且使吸收峰强度大大减小。量子限制效应使光吸收峰强度随着量子点尺寸的减小而增强,并且随着量子点尺寸的减小,吸收光谱发生蓝移现象。     

Epitaxial Growth of Large‐Scale Orthorhombic CsPbBr3 Perovskite Thin Films with Anisotropic Photoresponse Property

Inorganic cesium lead halide perovskite (CsPbX₃, X = Cl, Br, I) is a promising material for developing novel electronic and optoelectronic devices. Despite the substantial progress that has been made in the development of large perovskite single crystals, the fabrication of high‐quality 2D perovskite single‐crystal films, especially perovskite with a low symmetry, still remains a challenge. Herein, large‐scale orthorhombic CsPbBr₃ single‐crystal thin films on zinc‐blende ZnSe crystals are synthesized via vapor‐phase epitaxy. Structural characterizations reveal a “CsPbBr₃(110)//ZnSe(100), CsPbBr₃[?110]//ZnSe[001] and CsPbBr₃[001]//ZnSe[010]” heteroepitaxial relationship between the covering CsPbBr₃ layer and the ZnSe growth substrate. It is exciting that the epitaxial film presents an in‐plane anisotropic absorption property from 350 to 535 nm and polarization‐dependent photoluminescence. Photodetectors based on the epitaxial film exhibit a high photoresponsivity of 200 A W^?1, a large on/off current ratio exceeding 10⁴, a fast photoresponse time of about 20 ms, and good repeatability at room temperature. Importantly, a strong polarization‐dependent photoresponse is also found on the device fabricated using the epitaxial CsPbBr₃ film, making the orthorhombic perovskite promising building blocks for optoelectronic devices featured with anisotropy.