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Recently, solution-processed quantum dot light-emitting diodes (QLEDs) have emerged as a promising candidate for next-generation lighting and display devices. However, when given a constant voltage or current, the QLEDs need a certain working time to reach their maximum brightness. Such positive aging challenge, dramatically reducing the response speed of the device and causing a luminescence delay, is urgent to be investigated and resolved. In the current work, we introduce a charge-storage layer architecture by inserting copper(I) thiocyanate (CuSCN) between the organic hole-injection layer and hole-transport layer. The extracted holes will be released during the next electrical signal stimulation to increase the efficiency of charge transport. As a result, the response speed of the QLEDs is improved by an order of magnitude. In addition, by inserting an inorganic CuSCN layer, the efficiency, lifetime, and environmental stability of red/green/blue full-color QLEDs are enhanced simultaneously. Moreover, this work provides a generic strategy for the fabrication of fast-response and high-efficiency full-color QLEDs without luminescence delay, which plays a critical role in the practical industrialization of QLEDs.

Sensory adaptation is an essential function for humans to live on the earth. Herein, a hybrid synaptic phototransistor based on the mixed-halide perovskite/organic semiconductor film is reported. This hybrid phototransistor achieves photosensitive performance including a high photoresponsivity over 4 × 103 A/W and an excellent specific detectivity of 2.8 × 1016 Jones. Due to the photoinduced halide-ion segregation of the mixed-halide perovskites and their slow recovery properties, the experience-history-dependent sensory adaptation behavior can be mimicked. Moreover, the light pulse width, intensity, light wavelength, and gate bias can be used to regulate the adaptation processes to improve its adaptability and perceptibility in different environments. The CsPbBrxI3-x/organic semiconductor hybrid films produced by spin coating are beneficial to large-scale fabrication. This study fabricates a novel solution-processable light-stimulated synapse based on inorganic perovskites for mimicking the human sensory adaptation that makes it possible to approach artificial neural sensory systems.

Memristors based on organic–inorganic halide perovskite have received intensive attention because of its solution-processability and defect-tolerant characteristics. But the lead element in perovskite is inevitably harmful to human body and environment. Herein, we report an e-synapse based on lead-free organic halide perovskite (CH3NH3)3Sb2Cl9 (MA3Sb2Cl9), which exhibits excellent mimic of biological synaptic characteristics, such as excitatory postsynaptic currents (EPSCs), inhibitory postsynaptic currents (IPSCs), and paired-pulse facilitation (PPF). Furthermore, the synaptic weight of the e-synapse is found to be dependent on the frequency of pulse stimulation. The charge conduction mechanism of the e-synapse is proposed based on the in-depth investigation of the electrical characteristics of the devices. This work demonstrates that lead-free organic perovskite MA3Sb2Cl9 provide a new perspective on engineering e-synapses for neuromorphic computing and have a great potential for environment-friendly artificial intelligence applications.

A novel amorphous structure coupling with ultra-fine nano α-Fe grains in the surface crystallization layer was fabricated successfully through composition regulation and proper quenching conditions. The microstructure of the newly formed surface crystallization layer and its effects on soft magnetic properties of FeMnCuMoCPSiB amorphous alloy were investigated systematically. The FeMnCuMoCPSiB amorphous alloy with surface α-Fe crystallization layers exhibits an excellent comprehensive performance of soft magnetic properties (SMPs) with high Bs of 1.67 T, low Hc of 1.6 A/m, and high μi of 9.3 × 103 at 1 kHz. The SMPs of the amorphous alloy is considerably superior to that of widely used commercial soft magnetic materials METGLAS 2605, promising a potential engineering application. It is noteworthy that a nanoscale surface precipitation was found in the alloy, which favors SMPs of the alloy.

The double-sided electron beam welding (EBW) was proposed to overcome the severe deterioration of mechanical properties and electrical conductivity of Al/Cu bilayer laminated composite in the single-sided EBW process. The results show that the sound butt joint was obtained via the double-sided EBW. For the double-sided EBW joint, the microstructures in the Cu and Al side welds were similar. In the weld edge, it consisted of well-developed columnar structures. In the weld center, the fine equiaxed structures formed. The results of scanning electron microscopy with energy-dispersive spectroscopy, electron backscatter diffraction and x-ray diffraction indicated that the interface zone consisted of Al2Cu IMC and (Al2Cu+α-Al) eutectic structure. Moreover, the tensile strength of the double-sided EBW joint was 116.9 ± 5.3 MPa, and the fracture position was at the center of the joint, which was approximately 93% of the base material strength and far superior to the performance of single-sided joints with Modes I (57.5 ± 3.7 MPa) and II (66.7 ± 4.6 MPa). Furthermore, the electrical conductivity of the double-sided EBW joint was 56.8 ± 0.4 MS/m, which could reach 99.3% of the base material conductivity and was significantly higher than that of single-sided joints with Modes I (38.5 ± 2.1 MS/m) and II (44.3 ± 1.7 MS/m), ensuring the functionality of the joint after double-sided EBW.

In conventional quantum dot light-emitting diodes (QLEDs), the organic charge transport materials are susceptible to erosion by water and oxygen, which would reduce the efficiency and lifetime of the devices. Herein, we modified the surface of the organic hole transport layer with an ultra-thin Al2O3 layer, which is deposited by using atomic layer deposition technique, to obtain the highly efficient and stable QLEDs. It is indicated that the ultra-thin Al2O3 interlayer plays a significant role in decreasing leakage current, suppressing exciton quenching and passivating the defects. The device with Al2O3 interface modification exhibits the maximum external quantum efficiency (EQE) of 20.8%, current efficiency (CE) of 21.6 cd A−1, and lifetime of 482000 h. In comparison with the control device, the EQE, CE and lifetime are improved by 31%, 32%, and 330%, respectively. The results indicate that the strategy of Al2O3 interface modification could provide an effective way for realizing highly efficiency QLED with long lifetime.

Anticounterfeiting techniques based on physical unclonable functions exhibit great potential in security protection of extensive commodities from daily necessities to high-end products. Herein, we propose a facile strategy to fabricate an unclonable super micro fingerprint (SMFP) array by introducing in situ grown perovskite crystals for multilevel anticounterfeiting labels. The unclonable features are formed on the basis of the differential transportation of a microscale perovskite precursor droplet during the inkjet printing process, coupled with random crystallization and Ostwald ripening of perovskite crystals originating from their ion crystal property. Furthermore, the unclonable patterns can be readily tailored by tuning in situ crystallization conditions of the perovskite. Three-dimensional height information on the perovskite patterns are introduced into a security label and further transformed into structural color, significantly enhancing the capacity of anticounterfeiting labels. The SMFPs are characterized with tunable multilevel anticounterfeiting properties, including macroscale patterns, microscale unclonable pattern, fluorescent two-dimensional pattens, and colorful three-dimensional information.

Simulating synaptic function and building brain-inspired computers have received widespread attention. The memristor is considered to be an electronic version of the synapse and an excellent element for creating a brand-new artificial intelligence system in the future. However, most memristor-based electronic synapses currently exhibit low stability due to complex resistance switching processes. Based on a controllable in-situ formation strategy that we were able to employ with atomic layer deposition, we fabricated electronic synapses based on Au@Al2O3 core-shell nanoparticles. Our device exhibited extremely reliable, stable, and durable performance and showed a capability to emulate biological synaptic behavior, including synaptic plasticity, long-term depression (LTD), long-term potentiation (LTP), amplitude dependence, and frequency dependence. This research provides a strategy for manufacturing highly-reliable electronic synapses for neuromorphic applications.

Summary Plasmonic colors enabled by resonant hot electrons offer unique advantages in imaging, display, and optical encryption applications. Although metasurfaces can show full colors with sub-wavelength spatial resolutions, it is challenging for them to generate dynamic colors. Herein, we report an approach to dynamically control the color of semiconducting nanoparticles with plasmonic properties by tuning their hot-electron lifetime from timescales of seconds to days. The color switch is realized by storing photogenerated electrons, which produce plasmons upon light excitation, in carbon nitride. A photochromic display based on long-lived hot electrons is demonstrated. Two-dimensional patterns with unlimited designs and feature sizes from micro- to macro-scale are generated through laser writing or photolithography and then can be erased by exposure to moisture or heat, hundreds of times without obvious destruction to the device. This work may expand the possibilities of using hot electrons for reversibly manipulating the colors of semiconductor nanoparticles with plasmonic properties.

The central nervous system sends a neural impulse through an efferent nerve system toward muscles to drive movement. In an electronically artificial neural system, the electronic neural devices and interconnections prevent achieving highly connected and long-distance artificial impulse transmission and exhibit a narrow bandwidth. Here we design and demonstrate light-emitting memristors (LEMs) for the realization of an optoelectronic artificial efferent nerve, in which the LEM combines the functions of a light receiver, a light emitter, and an optoelectronic synapse in a single device. The optical signal from the pre-LEM (presynaptic membrane) acts as the input signal for the post-LEM (postsynaptic membrane), leading to one-to-many transmission, dynamic adjustable transmission, and light-trained synaptic plasticity, thus removing the physical limitation in artificially electronic neural systems. Furthermore, we construct an optoelectronic artificial efferent nerve with LEMs to control manipulators intelligently. These results promote the construction of an artificial optoelectronic nerve for further development of sensorimotor functionalities.

In this letter, we report the high-performance quantum dot light-emitting diodes (QLEDs) with a hybrid hole injection layer (HIL) by doping MoOx into poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS). By this method, the Fermi level of HIL increases from 4.9 to 5.3 eV, allowing better energy level matching and more efficient hole injection capability. The resultant devices exhibit maximum current efficiency of 18.6 cd/A and peak external quantum efficiency of 18.2%, almost 1.5-folds higher than those (12.7 cd/A and 12.3 %) of the control device based on pristine PEDOT:PSS HIL. Most importantly, the hydrophobicity of PEDOT: PSS on transparent conductive oxide can be dramatically improved upon MoOx doping, which provides promising potential in ink-jet printing for large-area fabrication of devices.

In this work, we report highly flexible QLEDs based on a quantum dots-polymer composite emitting layer. Conventional quantum dot films exhibit cracks after rough bending. Herein, polymethyl methacrylate (PMMA) was doped into quantum dot solution, acting as binder for neighboring quantum dots. In addition, PMMA can be serving as an electron blocking layer due to its insulating property, and then balancing the charge recombination and improving device performance. The flexible QLEDs have excellent mechanical properties with an ultimate bend radius of 1.5 mm, and they show no significant performance degradation after 500 times bending with radius of 4 mm. The flexible QLEDs exhibit high performance with maximum luminance of 14880 cd/m2 and maximum current efficiency of 21.3 cd/A.

An electronic synapse (e-synapse) based on memristive switching is a promising electronic element that emulates a biological synapse to realize neuromorphic computing. However, the complex resistive switching process it relies on hampers the reproducibility of its performance. Thus, achievement of a reproducible electronic synapse with a high rate of finished products has become a significant challenge in the development of an artificial intelligent circuit. Here, we demonstrate an ultrathin e-synapse having high yield (>95%), minimal performance variation, and extremely low power consumption based on an Al2O3/graphene quantum dots/Al2O3 sandwich structure that was fabricated using atomic layer deposition. The e-synapse showed both high device-to-device and cycle-to-cycle reproducibility with high stability, endurance, and switching uniformity, because the essential synaptic behaviors could be observed. This implementation of an e-synapse with an Al2O3/graphene quantum dots/Al2O3 structure should intensify motivation for engineering e-synapses for neuromorphic computing. Circuits that emulate the actions of biological synapses can be fabricated from devices known as quantum tunnel junctions. Fushan Li from China’s Fuzhou University, Tae Whan Kim from Korea’s Hanyang University, and colleagues produced an ‘e-synapse’ where a thin insulating film prevents electrons from moving through a circuit, except for a small number that jump across the barrier through quantum tunneling. When the researchers embedded graphene quantum dots in the film, they found that these nanoparticles switched the device between low and high resistance states by either trapping or releasing tunneling electrons. This allows the circuit to mimic certain functions of the brain; the gradual accumulation of electrons and their spontaneous release, for example, occurred on timeframes similar as seen in short-term memory loss. The team’s manufacturing scheme yielded devices with high stability and reproducibility. This article demonstrates an ultrathin e-synapse having high yield, minimal performance variation, and extremely low power consumption based on a Al2O3/graphene quantum dots/Al2O3 sandwich structure that was fabricated by using atomic layer deposition. It showed both high device-to-device and cycle-to-cycle reproducibility with high stability, endurance, and switching uniformity, because of which the essential synaptic behaviors could be observed. This implementation of an e-synapse with an Al2O3/graphene quantum dots/Al2O3 structure should intensify motivation for engineering e-synapses for neuromorphic computing.

In this paper, the aqueous solution-processed molybdenum oxide (sMoOx) as an efficient hole injection layer for flexible quantum dot light emitting diodes (QLEDs) was prepared using a simple, low-cost and non-toxic solution method. Compared to the traditional device used poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) as hole injection layer, the flexible QLED with modified sMoOx film has a higher maximum current efficiency, 5.46 cd/A. In addition, the stability and lifetime of flexible devices are improved effectively with the use of inorganic molybdenum oxide as hole injection layer, and they presented excellent flexibility through the repeated mechanical bending test at 5 mm radius of curvature.

Incorporating security labels with physical unclonable functions (PUFs) into products is considered as the most effective anti-counterfeiting measure. Here we reported a PUF-based security label composed of random colorful patterns. The security label was fabricated through self-assembly of coordination polymers – a cupric bromide complex of pyrazine 1,4-dioxide – on lithographically defined plasmonic surfaces. The coordination polymer exhibits excitation wavelength dependent fluorescence fingerprints, which enables encoding spectral information in the polymer. The fluorescence peaks of each spectrum can be easily converted to a unique anti-counterfeiting barcode. The developed security label also carries 2D graphical information, which can be visualized under bright-field, dark-field and fluorescence multifunctional microscopy. It is multicolored with high contrast under the bright/dark-field modes and single color under fluorescence mode. The multicolors originate from polymer-thickness dependent optical interference. The encryption with colors on a 50 μm square produces a minimum of 3739 PUF codes for the realized authentication system. Moreover, we developed a convenient and reliable authentication strategy based on the computer vision technique to verify the colorful PUF patterns with different definition, rotation angles, brightness, magnification and a mixture of these factors. A high correct validation rate of 100% is achieved using a match threshold of 0.3.

Low-power complementary organic circuits need to combine p-channel organic field-effect transistors (OFETs) and n-channel OFETs, which are based on p-type and n-type organic semiconductors, respectively. Unfortunately, the performance of n-type organic semiconductors still lags behind that of p-type organic semiconductors. In this work, the performance of solution-processed n-type OFETs was improved via a facile effective route, by blending a p-type organic semiconductor into the n-type polymer semiconductor. The effect of the p-type organic semiconductor additive on the morphology and charge transport was systematically investigated. It showed that the mobility, on/off ratio and stability of the n-type OFETs were significantly improved with incorporation of the p-type semiconductor. The p-type organic semiconductor functioned as a trap center for minority holes and decreased the trap density of the dielectric surface, resulting in an enhancement of the OFET performance. Moreover, blending with an appropriate amount of p-type organic semiconductor also benefited to reset polymer semiconductors stacking order into the direction that promoted charge transport. However, excess p-type semiconductor addition deteriorated the n-channel characteristics due to the formation of a percolation network, providing a pathway for hole transport. To the best of our knowledge, this is the first report about improving the performance of n-type polymer transistors by simply blending with a p-type organic semiconductor.

The emerging multilayer colloidal quantum dot light emitting diodes (QLEDs) comprise excellent intrinsic properties, such as narrow emission bandwidth, wide color gamut and solution processability, all of which is consistent with the requirement of advanced panel display device and their low-cost production process. But inferior blue QLEDs performance has impeded the commercialization of QLED display panel. Herein, polyvinylpyrrolidone (PVP) was doped into the electron transport layer where PVP functions as electron blocking material and separates zinc oxide nanoparticles (ZnO NPs) from each other to reduce electron injection, achieving charge balance in blue QLED emitting layer. With this method, the device performance obtained significant improvement. The maximum brightness of the devices reached 22800 cd m−2, and the external quantum efficiency reached 2.95%.

Optical security labels play a significant role in protecting both our wealth and health. However, simultaneously meeting the requirements including low-cost fabrication, easy detection, and high-level security is still challenging for security labels. Here, we design an unclonable anti-counterfeiting system with triple-level security by using the inkjet printing technique, which can be authenticated by naked eyes, a portable microscope, and a fluorescence microscope. These labels are achieved by printing microscale quantum dot (QD) ink droplets on premodified substrates with random-distributed glass microspheres. Due to the unique capillary action induced by the glass microspheres, QDs in the ink droplets are deposited around the microspheres, forming microscale multicircular patterns. Multiple pinning of QDs at the three-phase contact lines appears during the evaporation of the droplet, resulting in the formation of a nanoscale labyrinthine pattern around the microspheres. The nanoscale labyrinth pattern and the microscale multicircular microsphere array, together with the printed macroscopic image, constitute a triple-level progressive anti-counterfeiting system. Moreover, the system is compatible with an artificial intelligence-based identification strategy that allows rapid identification and verification of the unclonable security labels.

The effects of melt temperature in range of 1150–1400 °C on amorphous structure, magnetic properties and magnetic structures of Fe–Si–B–C amorphous ribbons were systematically investigated. The results of high-resolution transmission electron microscopy confirm that there exist a number of metastable nano-scales clusters in the quenched ribbons spinning at low melt temperature (1150 and 1300 °C). The measurement of flash differential scanning calorimetry finds that the thermal stability of the quenched ribbons notably increases with melt temperature elevating, also implying that higher melt temperature favors the higher degree of amorphization for the alloy. During the crystallization annealing process, the metastable Fe23(B, C)6 phase is preferentially precipitated at high melt temperature (1400 °C). The magnetic structure analyzed by magnetic force microscope reveals that a wide and uniform distribution of domain can be obtained in the alloy spun at high melt temperature (1400 °C), and that the domain size (width and length-breadth ratio of domain) is well correlated with coercivity and effective permeability. These current results provide important insights into the correlation between melt temperature and magnetic structure of Fe-based amorphous ribbons and are helpful to guide the production of Fe-based amorphous ribbons with homogeneous and stable amorphous structure from the technical level.

The relaxation kinetics and phase transformations of the confined D-mannitol (DM) in nanoporous alumina are studied in-situ using a high-precision nano-calorimeter. We find that the crystallization behavior can be suppressed when it is confined in nanopores smaller than 50 nm. The confined DM glass has a much smaller fragility (~76) than free DM glass (~125), confirming the enhanced glass-forming ability. It is intriguing that during isothermal annealing both the confined and free DM glasses relaxation kinetics experience two relaxation stages that have distinct activation energies. The relaxation activation energy of the confined glass is about 25%-29% smaller than the free glass, which is attributed to the reduced dimensionality. The abnormal kinetics observed in the confined DM glass open a new avenue for preparing stable glasses.

The development of electronic-skin (e-skin) with artificial tactile-perception is crucial for emerging artificial-intelligence systems. However, considering the relatively simple function of existing e-skins, their performances still have much room for improvement. Here, a cuttable, transparent, stretchable, and lightweight e-skin that functions on the basis of the triboelectric effect is demonstrated. Well-designed micro-gaps are introduced to make the e-skin respond sensitively to various mechanical stimulations, including pressing, stretching, folding, and twisting. Ag nanowires coated with graphene quantum dots are employed as the electrode, as well as the friction layer, to increase the sensitivity to external mechanical stimulations. Self-powered, smart, artificial fingers with tactile sensation to monitor the actions of the fingers were fabricated to demonstrate the potential application of our newly developed e-skin. The architecture and the material system of the device demonstrated in this work will promote the development of human-machine interfaces and intelligent machines.

Asynchronous responses of mechanical and magnetic properties to structure relaxation for the Fe71Nb6B23 bulk metallic glass were systematically investigated. It is interesting that this ternary alloy can combinedly exhibit outstanding magnetic and mechanical properties, especially good ductility, after optimally annealing in structure relaxation stage for eliminating the internal stress and homogenizing the microstructure. The alloy exhibits low coercive force of 1.6 A/m, high effective permeability of 15 × 103, high fracture strength of 4.2 GPa and good plastic strain of 1.8%. It is also found that responses of mechanical and magnetic properties to structure relaxation are asynchronous. The glass transition and crystallization will greatly deteriorate the magnetic and mechanical properties. Here we propose a physical picture and demonstrate that the primary structure factors determining magnetic and mechanical properties are different. This work will bring a promising material for application and a new perspective to study the effect of annealing-induced structure relaxation on mechanical and magnetic properties.

Fe-Co-Ni-Si-B high entropy amorphous alloys composites (HEAACs), which containing high entropy solid solution phase in amorphous matrix, show good soft magnetic properties and bending ductility even in optimal annealed state, were successfully developed by melt spinning method. The crystallization phase of the HEAACs is solid solution phase with body centered cubic (BCC) structure instead of brittle intermetallic phase. In addition, the BCC phase can transformed into face centered cubic (FCC) phase with temperature rise. Accordingly, Fe-Co-Ni-Si-B high entropy alloys (HEAs) with FCC structure and a small amount of BCC phase was prepared by copper mold casting method. The HEAs exhibit high yield strength (about 1200 MPa) and good plastic strain (about 18%). Meanwhile, soft magnetic characteristics of the HEAs are largely reserved from HEAACs. This work provides a new strategy to overcome the annealing induced brittleness of amorphous alloys and design new advanced materials with excellent comprehensive properties.

A solution-processed molybdenum oxide (MoOx) as the hole injection layer (HIL) by doctor-blade coating was developed to improve the efficiency and lifetime of red-emitting quantum-dot light-emitting diodes (QD-LEDs). It has been demonstrated that by adding isopropyl alcohol into the MoOx precursor during the doctor-blade coating process, the morphology, composition, and the surface electronic structure of the MoOx HIL could be tailored. A high-quality MoOx film with optimized charge injection was obtained, based on which all-solution-processed highly efficient red-emitting QD-LEDs were realized by using a low-cost doctor-blade coating technique under ambient conditions. The red QD-LEDs exhibited the maximum current efficiency and external quantum efficiency of 16 cd/A and 15.1%, respectively. Moreover, the lifetime of red devices initializing at 100 cd/m2 was 3236 h under ambient conditions, which is about twice as long as those with a conventional poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) H...

When portability, low cost, and green energy requirements are considered, the search for an electricity generator harvesting environmental energy based on available cheap commercial materials and simple fabrication techniques becomes significantly important. In this study, the capability of ultrasoft and cuttable paper-based triboelectric nanogenerator (P-TENG) to harvest mechanical energy is demonstrated. The P-TENG maintains the excellent softness of tissue paper and has the characteristics of light weight (~ 87 g/m2), high electric conductivity (6 Ω/square), and low cost (~ $3.00/m2). More importantly, the P-TENG can be cut by the end-user to modify its size and shape and still function properly. The mechanical energies available during cleaning processes, the energy associated with the body's motion, sound energy, and wind energy can be directly harvested by using the P-TENG. The high portability of the P-TENG, the simple and scalable fabrication processes, low cost, and its ability to harvest mechanical energy make the P-TENG important for the development of green, portable, energy-harvesting devices.

In this paper, a centimeter-size Zr-Cu-Al-Nb bulk metallic glass (BMG) with high notch toughness of 107±13 MPa∙m0.5 was designed and fabricated by copper mold casting. With 1% Nb substitution for Zr in Zr48Cu45Al7 glass forming alloy, the glass forming ability (GFA) and toughness of the BMG were enhanced significantly. The coexistence of nano-crystallization and phase separation in the glassy matrix was observed in Zr47Cu45Al7Nb1, which would possibly lead to the high toughness of this alloy due to the easy and populous nucleation of shear bands and the increasing resistance of shear band propagation. The influences of nano-crystallization and phase separation on the toughness of BMGs are discussed in detail. The strategy utilized in this study provides a novel approach in search for new BMGs with high toughness and good GFA.

The effect of Fe content on crystallization behavior and soft magnetic properties in Fe75.8+xSi9.3-xB8.9P3Nb2.5Cu0.5 (x = 0 ~ 7 at.%) alloys were investigated. The phase structure identified by XRD reveals that the glass forming ability (GFA) of alloys decreases with Fe increasing. TEM results confirm that the non-uniform structure of as-cast alloys and high Fe content are beneficial to the rapid nucleation of α-Fe when nucleation element of Cu is a constant, but the ability of Nb to hinder the growth of α-Fe grains is weakened, which will lead to the coercivity (Hc) to be highly sensitive to annealing temperature (Ta).

The ability to combine the color-tunability capability of natural organisms with a memory function in a single device is highly desired and holds promise for potential applications such as intelligent artificial skin and human-machine interfaces. In this work, we propose a universal strategy to realize color-tunable skin with the compound function of memory by ingeniously integrating a memristor interface into a flexible quantum-dot light-emitting device. The devices developed using this strategy have multiple responses to electrical and light stimulations and can easily change their color over a wide range from red to green. Moreover, these color-tunable devices can mimic the unique function of “once bitten, twice shy” to enhance self-protection, and their color tunability is consistent with the memory-forgetting curve proposed by psychologists.

Recently, perovskite quantum dots (PQDs) were employed as promising emitters in light-emitting diode devices (LEDs) mainly owing to their marvelous photoelectronics properties. However, these perovskite QLEDs suffered from the inefficient performance, especially their serious efficiency roll-off probably due to the exciton recombination dynamic in the interface of PQDs films and charge imbalance resulting from low electrical transportation. Herein, sodium dodecyl sulfate (SDS) was effectively introduced to synthesize PQDs with many excellent properties and eventually suppressed the efficiency roll-off of QLEDs. SDS-based PQDs films exhibited obviously enhanced radiative recombination, reduced trap density, and increased carrier mobility, especially the transportation of electrons. Therefore, the charge carrier was balanced at high current density together with the remarkably suppressed efficiency roll-off. QLEDs fabricated by SDS-capped PQDs exhibited significantly improved maximum brightness of 193,810 cd/m2, and achieve the external quantum efficiency of 10.13%. More importantly, the EQE roll-off of QLED optimized in the thickness of emitting layer was only 1.5% at the current density of 200 mA/cm2, representing a prominent achievement of our strategy.

In this work, Fe83+x(B4P8C4)16-xCu1 (x = 0, 1, 1.5 and 2 at. %) alloy system with amorphous/α-Fe hierarchic structures in as-cast state were artificially designed. The microstructure, crystallization kinetics, nanocrystalline structure, and magnetic properties of the alloys were systematically investigated. And the structural mechanism for the magnetic properties of these alloys was discussed. It is shown that the structure is evolved from full amorphous to amorphous/α-Fe dual-phase microstructure in the free surface side, and/or roller side layer with Fe content increasing. The formation of hierarchic structure decreases the activation energies of onset and peak crystallization of α-Fe phase, and increases the size of nanocrystalline grains, and subsequently is beneficial to improve the Bs of alloys. The Hc of alloys increases due to the formation of hierarchic structure, whereas this effect is gradually eliminated by the annealing process at the suitable crystallization annealing temperature (Ta). Typically, Fe85B3.5P7C3.5Cu1 nanocrystalline alloy exhibit the Bs of 1.86T and Hc of 5.7 A/m after annealing at 723 K. High Fe bearing alloys have lath domain structure with stronger orientation preference in as-cast state, and transformed into labyrinth packing with thinner spacing after structural relaxation annealing, demonstrating that hierarchic structure leads to the high magnetic anisotropy in the alloys.

Inkjet printing has been considered as a promising technique to achieve large-scale display panel with pixelated RGB quantum dots, to which the uniform quantum dots layer is of great importance. In this work, we exhibit our recent works of high-quality inkjet-printed red and green quantum dots (QDs) layer and fabrication of quantum dot light-emitting diodes (QLEDs) with normal architecture.

Construction of intramolecular π-π packing between cyclometalated and ancillary ligand have been proved to be a feasible way to design cationic Ir(III) phosphors for stable light-emitting electrochemical cells (LECs). Employing blue-green (C1) and yellow-emitting (C2) Ir(III) complexes as emitters, in which such π-π interactions between ligands occur, the stable and efficient LECs with peak current efficiency of 21.9 cd/A and 20.3 cd/A, respectively, were realized. To achieve the white electroluminescence, herein, a new red-emitting cationic Ir (III) complex (C3) using 2-(5-phenyl-2-phenyl-2H-1,2,4-triazol-3-yl)pyridine as ancillary ligand was designed and synthesized. A warm white light emitting, by doping C3 into the blue-green emitting C1, exhibits the current efficiency of 10.1 cd/A. In addition, the obtained LECs are more stable than those of previous reports due to presence of intrinsic super-cage structures in the systems. The results indicate that the efficient white LECs hold promising applications in the practical solid state lighting.

Tristable switching nonvolatile memory (NVM) devices based on graphene quantum dots (GQDs) sandwiched between multi-stacked poly (methyl methacrylate) (PMMA) layers were fabricated on indium-tin-oxide (ITO)-coated glass substrates by using a solution-processed method. Current-voltage (I-V) curves at 300 K for the silver nanowire/PMMA/GQD/PMMA/GQD/PMMA/ITO/glass devices showed tristable switching currents with high-resistance, intermediate-resistance, and low-resistance states. The device's cycling endurance of the three resistance states remained stable with a distinguishable value for each resistance state over 1000 cycles, and the obtained retention results showed well-distinguished resistance states without degradation for up to 1 × 104 s. Schottky emission, Poole-Frenkel emission, trapped-charge limited-current, and ohmic conduction were proposed as the dominant conduction mechanisms for the fabricated NVM devices based on the obtained I-V characteristics. The described energy-band diagrams confirm the proposed conduction band mechanisms.

(Fe0.76Si0.09B0.1P0.05)99.3&minus, xNbxCu0.7 (x = 0&ndash, 1.5 at. %) bulk nanocrystalline alloys were prepared to investigate the alloying effects of Nb on glass forming ability, thermal stability, soft magnetic properties, and crystallization behavior. It was found that the amorphous forming ability was greatly improved with the addition of minor Nb. The thermal stability of Nb-containing alloy was significantly improved because the initial crystallization temperature and crystallization activation of the primary phase were obviously better than that of the Nb-free alloy. Further, the larger intervals of two-phase crystallization temperature and the significantly higher activation energy of crystallization of the second phase in the Nb-containing alloys favor the formation of a single &alpha, Fe(Si) nanocrystalline structure. Moreover, Nb-containing alloys exhibit excellent soft magnetic properties, including high saturation magnetization of 1.42&ndash, 1.49 T, low coercivity of around 1.0 A/m, and high permeability of about 18,000 at 1 kHz, which makes the alloys promising soft magnetic materials for industrial applications.

The possibility to engineer the van der Waals interactions between graphene layers is crucial for controlling the electronic properties. Using epitaxial graphene with preferential orientations grown on the C-face 6H-SiC as a prototype, we have addressed the annealed structural reconfiguration of graphene layer in view of the evolutions of surface ripples and relative rotation angle (RRA) between lattices. It was found that the heat treatment of graphene layers under vacuum deformed the arcuate ripple surface and subsequently split one ripple into parallel twin pleats, which drastically increased the strains in the films. The originally oriented graphene layers, with small RRA between adjacent layers, were rearranged by the annealing resulting in disordered orientations and larger RRA. After a sufficient annealing, the compressive stress stored in the films was well released to give undistorted graphene lattices. The vacuum annealing is an effective treatment for irreversibly relaxing the graphene structure.

In this paper, O was added in Zr50Ti4Y1Al10Cu25Ni7Co2Fe1 complex multicomponent bulk metallic glass (CMBMG) with concentrations of 0.12 at.% and 0.45 at.%, and the microstructure, thermal stability and mechanical properties of these O-containing alloys were investigated in detail. It is found that, O element promotes the formation and growth of nanocrystals in the glassy matrix, and the structure of nanocrystalline phase changes from BCC to FCC with the increase in O content. Moreover, even at high Oxygen concentration, the alloy still shows excellent resistance to O-induced brittleness. This work is beneficial for better understanding the correlation between O and nanocrystal formation in CMBMGs, which provides a novel insight for further development of this series of alloys.

The effects of Co content on the thermal stability, soft-magnetic properties, corrosion resistance and mechanical properties of (Fe1-xCox)86Ni1B13 (x = 0–0.25) amorphous alloys were systematically investigated. Adequate Co addition can significantly increase saturation magnetic flux density (Bs). Extremely high Bs of 1.78–1.92 T was obtained when Co content was added in the range of x = 0.05–0.25. Besides, the Curie temperature (Tc) increases markedly with the introduction of Co, exhibiting the high thermal stability of soft magnetic properties. Compared with x = 0 (Co-free) alloys, the Tc of x = 0.1 (0.1Co) alloy increases more than 100 K, far exceeding the first crystallization temperature. There is also an obvious increase in temperature intervals between the two exothermic peaks of crystallization with Co content, implying high thermal stability of the Co-containing alloys. In addition, the corrosion resistance of 0.1Co alloy was also improved compared with the Co-free alloy. Among the (Fe1-xCox)86Ni1B13 amorphous alloys, the one with 0.1Co simultaneously exhibits high Bs of 1.87 T and low Hc of 10 A/m, as well as good bending ductility at annealed state. Moreover, the underlying mechanisms of the good ductility of the 0.1Co alloy annealed under the optimal condition was also discussed from the perspective of atom bonding nature. The combination of extremely high Bs and low Hc in conjunction with good manufacturability makes the (Fe0.9Co0.1)86Ni1B13 alloys promising soft-magnetic materials for potential applications.

The technological realization of wearable triboelectric generators is attractive because of their promising applications in wearable self-powered intelligent systems. However, the low electrical conductivity, the low electrical stability, and the low compatibility of current electronic textiles (e-textiles) and clothing restrict the comfortable and aesthetic integration of wearable generators into human clothing. Here, we present high-performance, transparent, smart e-textiles that employ commercial textiles coated with silver nanowire/graphene sheets fabricated by using a scalable, environmentally friendly, full-solution process. The smart e-textiles show superb and stable conduction of below 20 Ω/square as well as excellent flexibility, stretchability, foldability, and washability. In addition, wearable electricity-generating textiles, in which the e-textiles act as electrodes as well as wearable substrates, are presented. Because of the high compatibility of smart e-textiles and clothing, the electricity-generating textiles can be easily integrated into a glove to harvest the mechanical energy induced by the motion of the fingers. The effective output power generated by a single generator due to that motion reached as high as 7 nW/cm(2). The successful demonstration of the electricity-generating glove suggests a promising future for polyester/Ag nanowire/graphene core-shell nanocomposite-based smart e-textiles for real wearable electronic systems and self-powered clothing.

Indium-tin-oxide (ITO) free, nonvolatile memory (NVM) devices based on graphene quantum dots (GQDs) sandwiched between polymethylsilsesquioxane (PMSSQ) layers were fabricated directly on polyethylene terephthalate (PET) substrates by using a solution process technique. Current-voltage (I-V) curves for the silver nanowire/PMSSQ/GQD/PMSSQ/poly(3,4-ethylenethiophene):poly(styrene sulfonate)/PET devices at 300 K showed a current bistability. The ON/OFF ratio of the current bistability for the NVM devices was as large as 1 × 104, and the cycling endurance time of the ON/OFF switching for the NVM devices was above 1 × 104 s. The Schottky emission, Poole-Frenkel emission, trapped-charge limited-current, and space-charge-limited current were dominantly attributed to the conduction mechanisms for the fabricated NVM devices based on the obtained I-V characteristics, and energy band diagrams illustrating the “writing” and the “erasing” processes of the devices.

In this paper, we reported a low temperature processed planar heterojunction perovskite solar cell employing silver nanowires as the top electrode and ZnO nanoparticles as the electron transport layer. The CH3NH3PbI3 perovskite was grown as the light absorber via two-step spin-coating technique. The as-fabricated perovskite solar cell exhibited the highest power conversion efficiency of 9.21% with short circuit current density of 19.75 mA cm−2, open circuit voltage of 1.02, and fill factor value of 0.457. The solar cell's performance showed negligible difference between the forward and reverse bias scan. This work paves a way for realizing low cost solution processable solar cells.

We report a simple solution-process route to realize ammonia (NH3) gas sensor based on graphene quantum dots (GQDs). Transmission electron microscopy analysis confirmed that the 8–10 nm GQDs were formed from multi-walled carbon nanotubes by using ultrasonication treatment. The as-fabricated gas sensor showed promising selectivity response when expose to NH3 ambient at room temperature. It is indicated that by adjusting the pH value of the aqueous GQDs in acidic and neutral, two types of gas sensors with contrary current responses could be obtained, which might be resulted from quantum confinement, edge effects and presence of functional groups on GQDs.

Fe73.5Cu1Nb3Si15.5B7 nanocrystalline alloys were prepared by using conventional one-step annealing process and two-step annealing process. It was found that two-step annealing process can effectively improve soft magnetic properties and optimize microstructure. By separately controlling the formation of Cu clusters and further optimize the nanocrystalline structure, Bcc α-Fe with the grain size of 13 nm is formed in samples pretreated at 400 °C and nanocrystallized at 560 °C for 1 h. The samples exhibit excellent magnetic properties, such as lower coercive force of 0.7 A/m, higher initial permeability of 9.16 × 104, lower core loss of 0.18 W/kg at 0.7 T and 400 Hz, and 0.5 W/kg at 0.7 T and 1 kHz, respectively. The microstructure and magnetic structure evolution during different annealing processes were investigated. Correlation among the magnetic properties, magnetic structures and the microstructures changes in two different crystallization processes was studied systematically.

In this paper, we demonstrate a simple solution-processed route to fabricate flexible blue organic light emitting diodes (OLEDs) with graphene as its bottom electrode on flexible polyethylene terephthalate (PET) substrate. The device structure consists of Al/Zinc oxide (ZnO)/poly(9,9-dioctylfluorene) (PFO)/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/Graphene/PET. The PFO as a blue emitter layer and the ZnO nanoparticles as electron transport layer were deposited by using spin-coating technique. The flexible blue OLEDs based on graphene anode exhibits a stable deep blue emission with a CIE color coordinates of (0.17, 0.17). This study suggests a simple fabrication approach to construct graphene electrode-based flexible blue organic light emitting diodes.

The effect of cooling rate on phase structure and magnetic properties of the Fe26.7Co28.5Ni28.5Si4.6B8.7P3 high entropy alloy (HEA) was investigated. The HEA forms into amorphous phase by melt spinning method at high cooling rate and FCC solid solution phase at low cooling rate. The soft magnetic properties of the amorphous phase (saturation magnetization Bs of 1.07T and coercivity Hc of 4 A/m) are better than that of the solid solution phase (Bs of 1.0 T and Hc of 168 A/m). In order to study the phase evolution of the present HEA, anneal experiments were conducted. It is found that crystallization products of amorphous phase are solid solution phase which constitute much of FCC and a small amount of BCC. BCC phase transforms into FCC phase, and then into BCC phase with the increase of annealing temperature.

The effect of P content on crystallization behavior, microstructure, magnetic domain structure, and magnetic properties of Fe81.5Si3B13-xP0.5+xC0.2Cu0.8Nb1 (x = 0, 1, 2, and 3 at. %) alloys have been investigated. The results of XRD and DSC suggest that the moderate increase in P content improves the amorphous forming ability (AFA) of the alloys and enlarges the temperature interval to 153 K between two crystallization peaks. The activation energy indicates that the relative increase in P content prompts the precipitation of α-Fe phase and improves the thermal stability. Through optimal annealing treatments, the nanocrystalline alloy with x = 3 exhibits excellent soft magnetic properties (SMPs), including high Bs above 1.65 T, high µe about 19000, low Hc below 3 A/m and P10/50 around 0.12 W/kg. The microstructures of the alloys annealed at optimal conditions were detected via XRD and TEM, the results of which show that harmonizing P and B not only refines grains but enhances the nanostructure homogeneity. The investigation with magneto-optical Kerr microscopy reveals the magnetic domain evolution of x = 3 alloy including stress domain removing, domain differentiating and broadening process.