Indium Phosphide‐Based Quantum Dots with Shell‐Enhanced Absorption for Luminescent Down‐Conversion

It is shown that admixing small amounts of cadmium into the shell of InP/ZnSe core/shell quantum dots results in an increased absorption of blue light and a limited redshift of the band‐edge emission. These effects reflect the reduced bandgap of (Zn,Cd)Se alloys and their smaller conduction‐band offset with InP. Nevertheless, adjusting the InP core size enables InP/ZnSe and InP/(Zn,Cd)Se quantum dots with identical emission characteristics to be made. Processing both materials into remote phosphor disks, it is demonstrated that the shell‐enhanced absorbance of InP/(Zn,Cd)Se has the double benefit of suppressing self‐absorption and reducing the amount of quantum dots by weight needed to attain a given blue‐to‐red color conversion.     

Amino‐Mediated Anchoring Perovskite Quantum Dots for Stable and Low‐Threshold Random Lasing

Halide perovskite quantum dots (Pe‐QDs) have been considered as outstanding candidates for photodetector, light‐emitting diode, and lasing applications, but these perspectives are being impeded by the severe stability, including both chemical and optical degradations. This study reports on amino‐mediated anchoring Pe‐QDs onto the surfaces of monodisperse silica to effectively depress the optical degradation of their photoluminescence (PL) and random lasing stabilities, hence achieving highly stable and low‐threshold lasing. An amination‐mediated nucleation and growth process is designed for the general and one‐pot synthesis of Pe‐QDs on the surfaces of silica spheres. The facile synthetic process, which can be finished within several minutes, insures scalable production. Surprisingly, almost no PL degradation is observed after 40 d storage under ambient conditions, even 80% PL intensity can be maintained after persistently illuminated by UV lamps for 108 h. Subsequently, extremely stable random lasing is achieved after storage for 2 months or over continuously optical pumping for 8 h. Such high PL and lasing stabilities originate from the isolation effects due to the effective anchoring, which separate the Pe‐QDs from each other and inhibit the photoinduced regrowth and deterioration. This work will also open the window of perovskite‐based multifunctional systems.     

Electrically Pumped White‐Light‐Emitting Diodes Based on Histidine‐Doped MoS2 Quantum Dots

MoS₂ quantum dots (QDs)‐based white‐light‐emitting diodes (QD‐WLEDs) are designed, fabricated, and demonstrated. The highly luminescent, histidine‐doped MoS₂ QDs synthesized by microwave induced fragmentation of 2D MoS₂ nanoflakes possess a wide distribution of available electronic states as inferred from the pronounced excitation‐wavelength‐dependent emission properties. Notably, the histidine‐doped MoS₂ QDs show a very strong emission intensity, which exceeds seven times of magnitude larger than that of pristine MoS₂ QDs. The strongly enhanced emission is mainly attributed to nitrogen acceptor bound excitons and passivation of defects by histidine‐doping, which can enhance the radiative recombination drastically. The enabled electroluminescence (EL) spectra of the QD‐WLEDs with the main peak around 500 nm are found to be consistent with the photoluminescence spectra of the histidine‐doped MoS₂ QDs. The enhanced intensity of EL spectra with the current increase shows the stability of histidine‐doped MoS₂ based QD‐WLEDs. The typical EL spectrum of the novel QD‐WLEDs has a Commission Internationale de l'Eclairage chromaticity coordinate of (0.30, 0.36) exhibiting an intrinsic broadband white‐light emission. The unprecedented and low‐toxicity QD‐WLEDs based on a single light‐emitting material can serve as an excellent alternative for using transition metal dichalcogenides QDs as next generation optoelectronic devices.     

Perovskite Quantum Dots and Their Application in Light‐Emitting Diodes

Perovskite quantum dots (PQDs) attract significant interest in recent years because of their unique optical properties, such as tunable wavelength, narrow emission, and high photoluminescence quantum efficiency (PLQY). Recent studies report new types of formamidinium (FA) PbBr₃ PQDs, PQDs with organic–inorganic mixed cations, divalent cation doped colloidal CsPb_1?xM_xBr₃ PQDs (M = Sn²⁺, Cd²⁺, Zn²⁺, Mn²⁺) featuring partial cation exchange, and heterovalent cation doped into PQDs (Bi³⁺). These PQD analogs open new possibilities for optoelectronic devices. For commercial applications in lighting and backlight displays, stability of PQDs requires further improvement to prevent their degradation by temperature, oxygen, moisture, and light. Oxygen and moisture‐facilitated ion migration may easily etch unstable PQDs. Easy ion migration may result in crystal growth, which lowers PLQY of PQDs. Surface coating and treatment are important procedures for overcoming such factors. In this study, new types of PQDs and a strategy of improving their stabilities are introduced. Finally, this paper discusses future applications of PQDs in light‐emitting diodes.     

半导体量子点玻璃的研究进展

介绍了半导体量子点材料禁阻类型,详细阐述了共熔法、溶胶-凝胶法、离子注入法等半导体量子点玻璃材料的制备方法,探讨了半导体量子点玻璃的尺寸效应、禁阻效应、库仑阻塞效应和非线性光学效应等特性及其未来应用前景.     

Enhancement of Fluorescence Emission for Tricolor Quantum Dots Assembled in Polysiloxane toward Solar Spectrum‐Simulated White Light‐Emitting Devices

Commercial white light‐emitting diodes (LEDs) have the undesirable characteristics of blue‐rich emission and low color rendering index (CRI), while the constituent quantum dots (QDs) suffer from aggregation‐induced fluorescence quenching and poor stability. Herein, a strategy is developed to assemble tricolor QDs into a polysiloxane matrix using a polymer‐mediated hybrid approach whereby the hybrid composite exhibits a significant enhancement of aggregation‐dispersed emission, outstanding photostability, high thermal stability, and outstanding fluorescence recovery. Using the as‐prepared hybrid fluorescent materials, the fabricated LEDs exhibit solar spectrum‐simulated emission with adjustable Commission Internationale de L'Eclairage coordinates, correlated color temperature, and a recorded CRI of 97. Furthermore, they present no ultraviolet emission and weak blue emission, thus indicating an ideal healthy and high‐CRI white LED lighting source.     

Monolayer Silane‐Coated,Water‐Soluble Quantum Dots

A one‐step method to produce ≈12 nm hydrodynamic diameter water‐soluble CdSe/ZnS quantum dots (QDs), as well as CdS/ZnS, ZnSe/ZnMnS/ZnS, AgInS₂/ZnS, and CuInS₂/ZnS QDs, by ligand exchange with a near‐monolayer of organosilane caps is reported. The method cross‐links the surface‐bound silane ligands such that the samples are stable on the order of months under ambient conditions. Furthermore, the samples may retain a high quantum yield (60%) over this time. Several methods to functionalize aqueous QD dispersions with proteins and fluorescent dyes have been developed with reaction yields as high as 97%.     

Ultrathin,Core–Shell Structured SiO2 Coated Mn2+‐Doped Perovskite Quantum Dots for Bright White Light‐Emitting Diodes

All‐inorganic semiconductor perovskite quantum dots (QDs) with outstanding optoelectronic properties have already been extensively investigated and implemented in various applications. However, great challenges exist for the fabrication of nanodevices including toxicity, fast anion‐exchange reactions, and unsatisfactory stability. Here, the ultrathin, core–shell structured SiO₂ coated Mn²⁺ doped CsPbX₃ (X = Br, Cl) QDs are prepared via one facile reverse microemulsion method at room temperature. By incorporation of a multibranched capping ligand of trioctylphosphine oxide, it is found that the breakage of the CsPbMnX₃ core QDs contributed from the hydrolysis of silane could be effectively blocked. The thickness of silica shell can be well‐controlled within 2 nm, which gives the CsPbMnX₃@SiO₂ QDs a high quantum yield of 50.5% and improves thermostability and water resistance. Moreover, the mixture of CsPbBr₃ QDs with green emission and CsPbMnX₃@SiO₂ QDs with yellow emission presents no ion exchange effect and provides white light emission. As a result, a white light‐emitting diode (LED) is successfully prepared by the combination of a blue on‐chip LED device and the above perovskite mixture. The as‐prepared white LED displays a high luminous efficiency of 68.4 lm W^?1 and a high color‐rendering index of Ra = 91, demonstrating their broad future applications in solid‐state lighting fields.     

Site‐Controlled InGaAs Quantum Dots with Tunable Emission Energy

Semiconductor quantum‐dot (QD) systems offering perfect site control and tunable emission energy are essential for numerous nanophotonic device applications involving spatial and spectral matching of dots with optical cavities. Herein, the properties of ordered InGaAs/GaAs QDs grown by organometallic chemical vapor deposition on substrates patterned with pyramidal recesses are reported. The seeded growth of a single QD inside each pyramid results in near‐perfect (<10 nm) control of the QD position. Moreover, efficient and uniform photoluminescence (inhomogeneous broadening <10 meV) is observed from ordered arrays of such dots. The QD emission energy can be finely tuned by varying 1) the pyramid size and 2) its position within specific patterns. This tunability is brought about by the patterning of both the chemical properties and the surface curvature features of the substrate, which allows local control of the adatom fluxes that determine the QD thickness and composition.