Highly Efficient Green ZnAgInS/ZnInS/ZnS QDs by a Strong Exothermic Reaction for Down‐Converted Green and Tripackage White LEDs

Highly efficient bright green‐emitting Zn?Ag?In?S (ZAIS)/Zn?In?S (ZIS)/ZnS alloy core/inner‐shell/shell quantum dots (QDs) are synthesized using a multistep hot injection method with a highly concentrated zinc acetate dihydrate precursor. ZAIS/ZIS/ZnS QD growth is realized via five sequential steps: a core growth process, a two‐step alloying–shelling process, and a two‐step shelling process. To enhance the photoluminescence quantum yield (PLQY), a ZIS inner‐shell is synthesized and added with a band gap located between the ZAIS alloy‐core and ZnS shell using a strong exothermic reaction. The synthesized ZAIS/ZIS/ZnS QDs shows a high PLQY of 87% with peak wavelength of 501 nm. Tripackage white down‐converted light‐emitting diodes (DC‐LEDs) are realized using an InGaN blue (B) LED, a green (G) ZAIS/ZIS/ZS QD‐based DC‐LED, and a red (R) Zn?Cu?In?S/ZnS QD‐based DC‐LED with correlated color temperature from 2700 to 10 000 K. The red, green, and blue tripackage white DC‐LEDs exhibit high luminous efficacy of 72 lm W^?1 and excellent color qualities (color rendering index (CRI, R_a) = 95 and the special CRI for red (R₉) = 93) at 2700 K.     

Over 30% External Quantum Efficiency Light‐Emitting Diodes by Engineering Quantum Dot‐Assisted Energy Level Match for Hole Transport Layer

In the study of hybrid quantum dot light‐emitting diodes (QLEDs), even for state‐of‐the‐art achievement, there still exists a long‐standing charge balance problem, i.e., sufficient electron injection versus inefficient hole injection due to the large valence band offset of quantum dots (QDs) with respect to the adjacent carrier transport layer. Here the dedicated design and synthesis of high luminescence Zn_1?x Cd_xSe/ZnSe/ZnS QDs is reported by precisely controlled shell growth, which have matched energy level with the adjacent hole transport layer in QLEDs. As emitters, such Zn_1?xCd_xSe‐ based QLEDs exhibit peak external quantum efficiencies (EQE) of up to 30.9%, maximum brightness of over 334 000 cd m^?2, very low efficiency roll‐off at high current density (EQE ≈25% @ current density of 150 mA cm^?2), and operational lifetime extended to ≈1 800 000 h at 100 cd m^?2. These extraordinary performances make this work the best among all solution‐processed QLEDs reported in literature so far by achieving simultaneously high luminescence and balanced charge injection. These major advances are attributed to the combination of an intermediate ZnSe layer with an ultrathin ZnS outer layer as the shell materials and surface modification with 2‐ethylhexane‐1‐thiol, which can dramatically improve hole injection efficiency and thus lead to more balanced charge injection.     

Highly Efficient Green Zn?Ag?In?S/Zn?In?S/ZnS QDs by a Strong Exothermic Reaction for Down‐Converted Green and Tripackage White LEDs

Highly efficient bright green‐emitting Zn? Ag? In? S (ZAIS)/Zn? In? S (ZIS)/ZnS alloy core/inner‐shell/shell quantum dots (QDs) are synthesized using a multistep hot injection method with a highly concentrated zinc acetate dihydrate precursor. ZAIS/ZIS/ZnS QD growth is realized via five sequential steps: a core growth process, a two‐step alloying–shelling process, and a two‐step shelling process. To enhance the photoluminescence quantum yield (PLQY), a ZIS inner‐shell is synthesized and added with a band gap located between the ZAIS alloy‐core and ZnS shell using a strong exothermic reaction. The synthesized ZAIS/ZIS/ZnS QDs shows a high PLQY of 87% with peak wavelength of 501 nm. Tripackage white down‐converted light‐emitting diodes (DC‐LEDs) are realized using an InGaN blue (B) LED, a green (G) ZAIS/ZIS/ZS QD‐based DC‐LED, and a red (R) Zn? Cu? In? S/ZnS QD‐based DC‐LED with correlated color temperature from 2700 to 10 000 K. The red, green, and blue tripackage white DC‐LEDs exhibit high luminous efficacy of 72 lm W^?1 and excellent color qualities (color rendering index (CRI, R _a) = 95 and the special CRI for red (R ₉) = 93) at 2700 K.     

Low Roll‐Off Perovskite Quantum Dot Light‐Emitting Diodes Achieved by Augmenting Hole Mobility

The external quantum efficiencies (EQEs) of perovskite quantum dot light‐emitting diodes (QD‐LEDs) are close to the out‐coupling efficiency limitation. However, these high‐performance QD‐LEDs still suffer from a serious issue of efficiency roll‐off at high current density. More injected carriers produce photons less efficiently, strongly suggesting the variation of ratio between radiative and non‐radiative recombination. An approach is proposed to balance the carrier distribution and achieve high EQE at high current density. The average interdot distance between QDs is reduced and this facilitates carrier transport in QD films and thus electrons and holes have a balanced distribution in QD layers. Such encouraging results augment the proportion of radiative recombination, make devices with peak EQE of 12.7%, and present a great device performance at high current density with an EQE roll‐off of 11% at 500 mA cm^?2 (the lowest roll‐off known so far) where the EQE is still over 11%.     

High‐Throughput Combinatorial Optimizations of Perovskite Light‐Emitting Diodes Based on All‐Vacuum Deposition

Light‐emitting diodes (LEDs) based on lead halide perovskites demonstrate outstanding optoelectronic properties and are strong competitors for display and lighting applications. While previous halide perovskite LEDs are mainly produced via solution processing, here an all‐vacuum processing method is employed to construct CsPbBr₃ LEDs because vacuum processing exhibits high reliability and easy integration with existing OLED facilities for mass production. The high‐throughput combinatorial strategies are further adopted to study perovskite composition, annealing temperature, and functional layer thickness, thus significantly speeding up the optimization process. The best rigid device shows a current efficiency (CE) of 4.8 cd A^?1 (EQE of 1.45%) at 2358 cd m^?2, and best flexible device shows a CE of 4.16 cd A^?1 (EQE of 1.37%) at 2012 cd m^?2 with good bending tolerance. Moreover, by choosing NiO_x as the hole‐injection layer, the CE is improved to 10.15 cd A^?1 and EQE is improved to a record of 3.26% for perovskite LEDs produced by vacuum deposition. The time efficient combinatorial approaches can also be applied to optimize other perovskite LEDs.     

One‐Step Preparation of Coaxial CdS–ZnS and Cd1–xZnxS–ZnS Nanowires

Preparation of coaxial (core–shell) CdS–ZnS and Cd_1–xZn_xS–ZnS nanowires has been achieved via a one‐step metal–organic chemical vapor deposition (MOCVD) process with co‐fed single‐source precursors of CdS and ZnS. Single‐source precursors of CdS and ZnS of sufficient reactivity difference were prepared and paired up to form coaxial nanostructures in a one‐step process. The sequential growth of ZnS on CdS nanowires was also conducted to demonstrate the necessity and advantages of the precursor co‐feeding practice for the formation of well‐defined coaxial nanostructures. The coaxial nanostructure was characterized and confirmed by high‐resolution transmission electron microscopy and corresponding energy dispersive X‐ray spectrometry analyses. The photoluminescence efficiencies of the resulting coaxial CdS–ZnS and Cd_1–xZn_xS–ZnS nanowires were significantly enhanced compared to those of the plain CdS and plain Cd_1–xZn_xS nanowires, respectively, owing to the effective passivation of the surface electronic states of the core materials by the ZnS shell.     

Efficient Near‐Infrared Light‐Emitting Diodes based on In(Zn)As–In(Zn)P–GaP–ZnS Quantum Dots

Near‐infrared (NIR) lighting plays an increasingly important role in new facial recognition technologies and eye‐tracking devices, where covert and nonvisible illumination is needed. In particular, mobile or wearable gadgets that employ these technologies require electronic lighting components with ultrathin and flexible form factors that are currently unfulfilled by conventional GaAs‐based diodes. Colloidal quantum dots (QDs) and emerging perovskite light‐emitting diodes (LEDs) may fill this gap, but generally employ restricted heavy metals such as cadmium or lead. Here, a new NIR‐emitting diode based on heavy‐metal‐free In(Zn)As–In(Zn)P–GaP–ZnS quantum dots is reported. The quantum dots are prepared with a giant shell structure, enabled by a continuous injection synthesis approach, and display intense photoluminescence at 850 nm with a high quantum efficiency of 75%. A postsynthetic ligand exchange to a shorter‐chain 1‐mercapto‐6‐hexanol (MCH) affords the QDs with processability in polar solvents as well as an enhanced charge‐transport performance in electronic devices. Using solution‐processing methods, an ITO/ZnO/PEIE/QD/Poly‐TPD/MoO₃/Al electroluminescent device is fabricated and a high external quantum efficiency of 4.6% and a maximum radiance of 8.2 W sr^?1 m^?2 are achieved. This represents a significant leap in performance for NIR devices employing a colloidal III–V semiconductor QD system, and may find significant applications in emerging consumer electronic products.     

Saturated and Multi‐Colored Electroluminescence from Quantum Dots Based Light Emitting Electrochemical Cells

Novel light emitting electrochemical cells (LECs) are fabricated using CdSe‐CdS (core‐shell) quantum dots (QDs) of tuned size and emission blended with polyvinylcarbazole (PVK) and the ionic liquid 1‐butyl‐3‐methylimidazolium hexafluorophosphate (BMIM‐PF₆). The performances of cells constructed using sequential device layers of indium tin oxide (ITO), poly(3,4‐ethylenedioxythiophene)‐poly(styrenesulfonate) (PEDOT:PSS), the QD/PVK/IL active layer, and Al are evaluated. Only color saturated electroluminescence from the QDs is observed, without any other emissions from the polymer host or the electrolyte. Blue, green, and red QD‐LECs are prepared. The maximum brightness (≈1000 cd m^‐2) and current efficiency (1.9 cd A^‐1) are comparable to polymer LECs and multilayer QD‐LEDs. White‐light QD‐LECs with Commission Internationale d'Eclairage (CIE) coordinates (0.33, 0.33) are prepared by tuning the mass ratio of R:G:B QDs in the active layer and voltage applied. Transparent QD‐LECs fabricated using transparent silver nanowire (AgNW) composites as the cathode yield an average transmittance greater than 88% over the visible range. Flexible devices are demonstrated by replacing the glass substrates with polyethylene terephthalate (PET).     

Suppressing Ion Migration Enables Stable Perovskite Light‐Emitting Diodes with All‐Inorganic Strategy

Stability issue is one of the major concerns that limit emergent perovskite light‐emitting diodes (PeLEDs) techniques. Generally, ion migration is considered as the most important origin of PeLEDs degradation. In this work, an all‐inorganic device architecture, LiF/perovskite/LiF/ZnS/ZnSe, is proposed to address this imperative problem. The inorganic (Cs_1?xRb_x)_1?yK_yPbBr₃ perovskite is optimized with achieving a photoluminescence quantum yield of 67%. Depth profile analysis of X‐ray photoelectron spectroscopy indicates that the LiF/perovskite/LiF structure and the ZnS/ZnSe cascade electron transport layers significantly suppress the electric‐field‐induced ion migrations of the perovskite layers, and impede the diffusion of metallic atoms from cathode into perovskites. The as‐prepared PeLEDs display excellent shelf stability (maintaining 90% of the initial external quantum efficiency [EQE] after 264 h) and operational stability (half‐lifetime of about 255 h at an initial luminance of 120 cd m^?2). The devices also exhibit a maximum brightness of 15 6155 cd m^?2 and an EQE of 11.05%.     

Organometal Halide Perovskite Quantum Dot Light‐Emitting Diodes

Organometal halide perovskites quantum dots (OHP‐QDs) with bright, color‐tunable, and narrow‐band photoluminescence have significant advantages in display, lighting, and laser applications. Due to sparse concentrations and difficulties in the enrichment of OHP‐QDs, production of large‐area uniform films of OHP‐QDs is a challenging task, which largely impedes their use in electroluminescence devices. Here, a simple dip‐coating method has been reported to effectively fabricate large‐area uniform films of OHP‐QDs. Using this technique, multicolor OHP‐QDs light‐emitting diodes (OQ‐LEDs) emitting in blue, blue‐green, green, orange, and red color have been successfully produced by simply tuning the halide composition or size of QDs. The blue, green, and red OQ‐LEDs exhibited, respectively, a maximum luminance of 2673, 2398, and 986 cd m^?2 at a current efficiency of 4.01, 3.72, and 1.52 cd A^?1, and an external quantum efficiency of 1.38%, 1.06%, and 0.53%, which are much better than most LEDs based on OHP films. The packaged OQ‐LEDs show long‐term stability in air (humidity ≈50%) for at least 7 d. The results demonstrate the great potential of the dip‐coating method to fabricate large‐area uniform films for various QDs. The high‐efficiency OQ‐LEDs also demonstrate the promising potential of OHP‐QDs for low‐cost display, lighting, and optical communication applications.     

2D Ruddlesden–Popper Perovskite Nanoplate Based Deep‐Blue Light‐Emitting Diodes for Light Communication

Ruddlesden–Popper perovskite, (PEA)₂PbBr₄ (PEA = C₈H₉NH₃), is a steady and inexpensive material with a broad bandgap and a narrow‐band emission. These features make it a potential candidate for deep‐blue light‐emitting diodes (LEDs). However, due to the weak exciton binding energy, LEDs based on the perovskite thin films usually possess a very low external quantum efficiency (EQE) of <0.03%. Here, for the first time, the construction of high‐performance deep‐blue LEDs based on 2D (PEA)₂PbBr₄ nanoplates (NPs) is demonstrated. The as‐fabricated (PEA)₂PbBr₄ NPs film shows a deep‐blue emission at 410 nm with excellent stability under ambient conditions. Impressively, LEDs based on the (PEA)₂PbBr₄ NPs film deliver a bright deep‐blue emission with a maximum luminance of 147.6 cd m^?2 and a high EQE up to 0.31%, which represents the most efficient and brightest perovskite LEDs operating at deep‐blue wavelengths. Furthermore, the LEDs retain over 80% of their efficiencies for over 1350 min under ≈60% relative humidity. The steady and bright deep‐blue LEDs can be used as an excitation light source to realize white light emission, which shows the potential for light communication. The work provides scope for developing perovskite into efficient and deep‐blue LEDs for low‐cost light source and light communication.     

Highly Efficient Quantum Dot Light‐Emitting Diodes by Inserting Multiple Poly(methyl methacrylate) as Electron‐Blocking Layers

This work presents a new device architecture integrating multiple poly(methyl methacrylate) (PMMA) electron‐blocking layers (EBL) in quantum dot light‐emitting diodes (QD‐LEDs). The device utilizes red‐emitting CdSe/ZnS QD with a novel structure where multiple PMMA EBLs are sandwiched between a pair of QD layers. A systematic optimization of QD‐LED structures has shown that a device including two PMMA and three QD layers performs the best, achieving a current efficiency of 17.8 cd A^?1 and a luminance of 194 038 cd m^?2. Numerical simulation of a simplified model of the proposed QD‐LED structure verifies that the structure consisting of two PMMA and three QD layers provides significant improvement in electroluminescent intensity. The simulation provides further insight into the origin of the effect of the PMMA EBL by showing that the addition of PMMA EBL reduces the electron leakage from the active QD region and enhances electron confinement, leading to an increased electron concentration in the QD active layers and a higher radiative recombination rate. The experimental and theoretical studies presented in this work demonstrate that multiple layers of PMMA can act as efficient EBLs in the fabrication of QD‐LEDs of improved performance.     

Transparent InP Quantum Dot Light‐Emitting Diodes with ZrO2 Electron Transport Layer and Indium Zinc Oxide Top Electrode

Because of outstanding optical properties and non‐vacuum solution processability of colloidal quantum dot (QD) semiconductors, many researchers have developed various light emitting diodes (LEDs) using QD materials. Until now, the Cd‐based QD‐LEDs have shown excellent properties, but the eco‐friendly QD semiconductors have attracted many attentions due to the environmental regulation. And, since there are many issues about the reliability of conventional QD‐LEDs with organic charge transport layers, a stable charge transport layer in various conditions must be developed for this reason. This study proposes the organic/inorganic hybrid QD‐LEDs with Cd‐free InP QDs as light emitting layer and inorganic ZrO₂ nanoparticles as electron transport layer. The QD‐LED with bottom emission structure shows the luminescence of 530 cd m^?2 and the current efficiency of 1 cd/A. To realize the transparent QD‐LED display, the two‐step sputtering process of indium zinc oxide (IZO) top electrode is applied to the devices and this study could fabricate the transparent QD‐LED device with the transmittance of more than 74% for whole device array. And when the IZO top electrode with high work‐function is applied to top transparent anode, the device could maintain the current efficiency within the driving voltage range without well‐known roll‐off phenomenon in QD‐LED devices.     

Highly Stable Colloidal “Giant” Quantum Dots Sensitized Solar Cells

Colloidal quantum dots (QDs) are widely studied due to their promising optoelectronic properties. This study explores the application of specially designed and synthesized “giant” core/shell CdSe/(CdS)_x QDs with variable CdS shell thickness, while keeping the core size at 1.65 nm, as a highly efficient and stable light harvester for QD sensitized solar cells (QDSCs). The comparative study demonstrates that the photovoltaic performance of QDSCs can be significantly enhanced by optimizing the CdS shell thickness. The highest photoconversion efficiency (PCE) of 3.01% is obtained at optimum CdS shell thickness ≈1.96 nm. To further improve the PCE and fully highlight the effect of core/shell QDs interface engineering, a CdSe_x S_1?x interfacial alloyed layer is introduced between CdSe core and CdS shell. The resulting alloyed CdSe/(CdSe_x S_1?x )₅/(CdS)₁ core/shell QD‐based QDSCs yield a maximum PCE of 6.86%, thanks to favorable stepwise electronic band alignment and improved electron transfer rate with the incorporation of CdSe_x S_1?x interfacial layer with respect to CdSe/(CdS)₆ core/shell. In addition, QDSCs based on “giant” core/CdS‐shell or alloyed core/shell QDs exhibit excellent long‐term stability with respect to bare CdSe‐based QDSCs. The giant core/shell QDs interface engineering methodology offers a new path to improve PCE and the long‐term stability of liquid junction QDSCs.     

Highly Efficient Non‐Doped Blue‐Light‐Emitting Diodes Based on an Anthrancene Derivative End‐Capped with Tetraphenylethylene Groups

A novel blue‐emitting material, 2‐tert‐butyl‐9,10‐bis[4‐(1,2,2‐triphenylvinyl)phenyl]anthracene ( TPVAn ), which contains an anthracene core and two tetraphenylethylene end‐capped groups, has been synthesized and characterized. Owing to the presence of its sterically congested terminal groups, TPVAn possesses a high glass transition temperature (155 °C) and is morphologically stable. Organic light‐emitting diodes (OLEDs) utilizing TPVAn as the emitter exhibit bright saturated‐blue emissions (Commission Internationale de L'Eclairage (CIE) chromaticity coordinates of x = 0.14 and y = 0.12) with efficiencies as high as 5.3 % (5.3 cd A^–1)—the best performance of non‐doped deep blue‐emitting OLEDs reported to date. In addition, TPVAn doped with an orange fluorophore served as an authentic host for the construction of a white‐light‐emitting device that displayed promising electroluminescent characteristics: the maximum external quantum efficiency reached 4.9 % (13.1 cd A^–1) with CIE coordinates located at (0.33, 0.39).     

PbS/CdS/ZnS Quantum Dots: A Multifunctional Platform for In Vivo Near‐Infrared Low‐Dose Fluorescence Imaging

Over the past decade, near‐infrared (NIR)‐emitting nanoparticles have increasingly been investigated in biomedical research for use as fluorescent imaging probes. Here, high‐quality water‐dispersible core/shell/shell PbS/CdS/ZnS quantum dots (hereafter QDs) as NIR imaging probes fabricated through a rapid, cost‐effective microwave‐assisted cation exchange procedure are reported. These QDs have proven to be water dispersible, stable, and are expected to be nontoxic, resulting from the growth of an outer ZnS shell and the simultaneous surface functionalization with mercaptopropionic acid ligands. Care is taken to design the emission wavelength of the QDs probe lying within the second biological window (1000–1350 nm), which leads to higher penetration depths because of the low extinction coefficient of biological tissues in this spectral range. Furthermore, their intense fluorescence emission enables to follow the real‐time evolution of QD biodistribution among different organs of living mice, after low‐dose intravenous administration. In this paper, QD platform has proven to be capable (ex vivo and in vitro) of high‐resolution thermal sensing in the physiological temperature range. The investigation, together with the lack of noticeable toxicity from these PbS/CdS/ZnS QDs after preliminary studies, paves the way for their use as outstanding multifunctional probes both for in vitro and in vivo applications in biomedicine.     

Magnetic/Fluorescent Barcodes Based on Cadmium‐Free Near‐Infrared‐Emitting Quantum Dots for Multiplexed Detection

Magnetic/fluorescent barcodes, which combine quantum dots (QDs) and superparamagnetic nanoparticles in micrometer‐sized host microspheres, are promising for automatic high‐throughput multiplexed biodetection applications and “point of care” biodetection. However, the fluorescence intensity of QDs sharply decreases after addition of magnetic nanoparticles (MNPs) due to absorption by MNPs, and thus, the encoding capacity of QDs becomes more limited. Furthermore, the intrinsic toxicity of cadmium‐based QDs, the most commonly used QD in barcodes, has significant risks to human health and the environment. In this work, to alleviate fluorescence quenching and intrinsic toxicity, cadmium‐free NIR‐emitting CuInS₂/ZnS QDs and Fe₃O₄ MNPs are successfully incorporated into poly(styrene‐co‐maleic anhydride) microspheres by using the Shirasu porous glass membrane emulsification technique. A “single‐wavelength” encoding model is successfully constructed to guide the encoding of NIR QDs with wide emission spectra. Then, a “single‐wavelength” encoding combined with size encoding is used to produce different optical codes by simply changing the wavelength and the intensity of the QDs as well as the size of the barcode microspheres. 48 barcodes are easily created due to the greatly reduced energy transfer between the NIR‐emitting QDs and MNPs. The resulting bifunctional barcodes are also combined with a flow cytometer using one laser for multiplexed detection of five tumor markers in one test. Assays based on these barcodes are significantly more sensitive than non‐magnetic and traditional ELISA assays. Moreover, validating experiments also show good performance of the bifunctional barcodes‐based suspension array when dealing with patient serum samples. Thus, magnetic/fluorescent barcodes based on NIR‐emitting CuInS₂/ZnS QDs are promising for multiplexed bioassay applications.     

Core/Shell PbSe/PbS QDs TiO2 Heterojunction Solar Cell

Quasi type‐II PbSe/PbS quantum dots (QDs) are employed in a solid state high efficiency QD/TiO₂ heterojunction solar cell. The QDs are deposited using layer‐by‐layer deposition on a half‐micrometer‐thick anatase TiO₂ nanosheet film with (001) exposed facets. Theoretical calculations show that the carriers in PbSe/PbS quasi type‐II QDs are delocalized over the entire core/shell structure, which results in better QD film conductivity compared to PbSe QDs. Moreover, PbS shell permits better stability and facile electron injection from the QDs to the TiO₂ nanosheets. To complete the electrical circuit of the solar cell, a Au film is evaporated as a back contact on top of the QDs. This PbSe/PbS QD/TiO₂ heterojunction solar cell produces a light to electric power conversion efficiency (η) of 4% with short circuit photocurrent (J_sc) of 17.3 mA/cm². This report demonstrates highly efficient core/shell near infrared QDs in a QD/TiO₂ heterojunction solar cell.     

Photoluminescence Tuning in Stretchable PDMS Film Grafted Doped Core/Multishell Quantum Dots for Anticounterfeiting

The development of new luminescent materials for anticounterfeiting is of great importance, owing to their unique physical, chemical, and optical properties. The authors report the use of color‐tunable colloidal CdS/ZnS/ZnS:Mn²⁺/ZnS core/multishell quantum dots (QDs)‐functionalized luminescent polydimethylsiloxane film (LPF) for anticounterfeiting applications. Both luminescent QDs and as‐fabricated, stretchable, and transparent LPF show blue and orange emission simultaneously, which are ascribed to CdS band‐edge emission and the ⁴T₁ → ⁶A₁ transition of Mn²⁺, respectively; their emission intensity ratios are dependent on the power‐density of a single‐wavelength excitation source. Additionally, photoluminescence tuning of CdS/ZnS/ZnS:Mn²⁺/ZnS QDs in hexane or embedded in LPF can also be realized under fixed excitation power due to a resonance energy transfer effect. Tunable photoluminescence of these flexible LPF grafted doped core/shell QDs can be finely controlled and easily realized, depending on outer excitation power and intrinsic QD concentration, which is intriguing and inspires the fabrication of many novel applications.     

Composition-tuned optical properties of CdSexS1-x and CdSexS1-x/ZnS QDs

The different compositions of the ternary alloyed CdSe_xS_1-x quantum dots(QDs) and CdSe_xS_1-x/ZnS core/shell quantum dots(CSQDs) have been synthesized by the chemical routes. The radii of these QDs were determined by transmission electron microscope(TEM). The optical properties of these QDs were investigated by the absorption and fluorescent measurement. It was found that the absorption and fluorescent emissions were tuned by the component ratio, and the...