Search

Spin optoelectronics is an indispensable key for the future development of spintronics. In conventional spin light emitting diodes (LEDs), spin‐polarized carrier pairs are injected electrically into the light emitting layer and create circularly polarized light (CPL). Generally, spin‐polarized carriers are accomplished using ferromagnetic contacts or applying an external magnetic field, which will produce several drawbacks, including low temperature operation, low spin‐polarized carriers injection efficiency, etc. To circumvent the existing shortcomings, here, an alternative approach is proposed and achieves spin‐polarized LEDs at room temperature based on quantum dots (QDs)/chiral metal‐organic framework heterojunction without using ferromagnetic contacts or magnetic fields. The spin‐polarized injected layer composed of self‐assembled monolayer (SAM)/Chiral‐MOF ([Sr(9,10‐adc)(DMAc)2]n)) film, which produces spin‐polarized holes with spin orientation, determining the polarization and strength of circularly polarized electroluminescence (CP‐EL). The spin‐QLED emits CP‐EL at a rate of 12.24% efficiency, which provides an excellent alternative to generate new functionality for conventional QLEDs. The approach is anticipated to be very useful, enabling to offer a general methodology for generating not yet realized spin optoelectronic devices. [ABSTRACT FROM AUTHOR]

Infrared-to-visible upconversion (IVU) possesses a variety of applications, spanning from bio-imaging to anti-counterfeiting, and has attracted great attention. However, the devices developed in previous studies suffer from several drawbacks, such as relatively weak optical absorption, requirement of a complicated design, and a costly fabrication process, which limit their potential practical application. To circumvent the existing difficulties, in this study, an IVU device based on infrared quantum dots (QDs) and a mixture of visible QD light-emitting diodes (QLEDs) with low operational voltage and multiple changeable visible colors is demonstrated. The emission color of this IVU-QLED can be easily manipulated under different input currents and power densities of incident infrared radiation. The IVU-QLED device can also be achieved with cost-effective and simple solution fabrication processes. In addition, this dual electrical-optical modulated IVU-QLED shows a fast response time. With the unexplored features of IVU, including infrared-visible upconversion, tunable visible color emission, dual functional modulation, and cost-effectiveness, the designed IVU-QLEDs shown here provide an alternative route for the development of untouched optoelectronic devices, which should be very useful and timely for future applications covering anti-counterfeiting, infrared sensing, bio-imaging, night vision, etc. [ABSTRACT FROM AUTHOR]

Inspired by animals in nature, such as chameleons, frogs, and cephalopods, the remarkable capability of changing one's skin color has drawn considerable interests due to its wide applications in camouflage, warning methods, and visual communications. Today, research on electronic skins (e‐skins), imitating biological skin by quantifying external stimuli, to mimic this unique color‐changing function has been achieved based on the integration of a matrix of displays and sensors; however, integrated systems possess bulky and complicated fabrication processes. Here, the first attempt to demonstrate a single user‐interactive e‐skin device with color‐changing response upon applied external strain is made, while using a cost‐effective and space‐saving method, which promises to open new possibilities for the development of next‐generation e‐skins with visual response. [ABSTRACT FROM AUTHOR]

In this study, novel three-dimensional (3-D) nanoscale structures and methodology are demonstrated for application in high-efficiency core–shell nanorod (NR) light-emitting diodes (LEDs). The key to our successful growth of the structures is the introduction of passivation, which can be used to selectively grow active layers in desired structures. Through the fabrication methodology, core–shell NR green LEDs exhibiting large nonpolar active region and homogeneous indium distributions without a point tip shape were achieved. Stable light emission at a central wavelength of 518 nm was achieved as the injected current increased to more than 40 mA. The improved NR LEDs exhibited a stable luminescence emission wavelength (blueshift of 62 nm) and low-efficiency droop (18.1%) at 200 mA. Our scheme is scalable and compatible with current technologies, which provides a new perspective for developing high-performance, 3-D nanoscale optoelectronic devices. [ABSTRACT FROM PUBLISHER]

Advanced materials that combine novel functionality and ease of applicability are central to the development of light-emitting diodes (LEDs), which is of ever increasing commercial importance. Here a new metal-insulator-semiconductor (MIS) LED structure that combines economical fabrication with novel device properties is reported. The presented MIS-LED consists of a graphene electrode on p-GaN substrate separated by an insulating SiO2 layer. It is found that the MIS-LED possesses a unique tunability of the electroluminescence spectra depending on the bias conditions. Tunnel injection from graphene into the p-GaN can explain the difference in luminescence spectra under forward and reverse bias. The demonstrated MIS-LED expands the use of graphene and also possibly allows the direct integration of light emitters with other circuit elements. [ABSTRACT FROM AUTHOR]

The resonant coupling between cadmium-free I-III-VI2 group quantum dots (QDs) and metal nanostructures has been investigated. Via a SiO2-packaging synthetic procedure, the emission intensity of green ZCIS/ZnS QDs can be greatly enhanced by three times through the localized surface plasmon of Au nanoparticles. Moreover, the bandwidth of the emission spectrum can be narrowed by 17 nm, and the resultant quantum yield is more than 50% which sets up the highest reported value up today for green I-III-VI2 QDs. Our strategy for the improved characteristics of emission spectrum may open a facile alternative for the development of cadmium-free QD light emitting diodes and other optoelectronic devices. [ABSTRACT FROM AUTHOR]

A new and general approach to achieving efficient electrically driven light emission from a Si-based nano p-n junction array is introduced. A wafer-scale array of p-type silicon nanotips were formed by a single-step self-masked dry etching process, which is compatible with current semiconductor technologies. On top of the silicon nanotip array, a layer of n-type ZnO film was grown by pulsed laser deposition. Both the narrow line width of 10 nm in cathodoluminescence spectra and the appearance of multiphonon Raman spectra up to the fourth order indicate the excellent quality of the ZnO film. The turn-on voltage of our ZnO/Si nanotip array is found to be ∼2.4 V, which is 2 times smaller than its thin film counterpart. Moreover, electroluminescence (EL) from our ZnO/Si nanotips array light-emitting diode (LED) has been demonstrated. Our results could open up new possibilities to integrate silicon-based optoelectronic devices, such as highly efficient LEDs, with standard Si ultralarge-scale integrated technology. [ABSTRACT FROM AUTHOR]