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One of the remarkable features of the cornea is its high transparency of incident light in the visible spectrum. However, how the transmittance evolving with corneal structure is still not fully understood. In this study, we measured changes in corneal transmittance between from eighth to nineteenth day during development and imaged the lamellae of corneal stroma by nonlinear microscopy. Our results indicate that the minimum corneal transparency is at thirteenth day. The transmittance of embryonic cornea after the Day 14 rises sharply until the Day 19. The development of early stage at the tenth day displayed wavy pattern of corneal stroma. In addition, when comparing the transmissivity of the adult and embryonic corneas, larger deviations at the lower wavelengths of 320–400 nm were found to be significant. Our findings indicate that structural changes are related to the development of transmittance and the mature progress of transmittance is still continuing after birth. [ABSTRACT FROM AUTHOR]

Discusses a study on the observation of the quantum confinement effect by using photothermal deflection spectroscopy and photoluminescence experiments of cadmium sulphide and cadmium selenide quantum dots. Analysis of quantum confinement effect; Measurement of absorption spectra; Source of ionization of microcrystals.

Presents a study which determined gap state density distribution in hydrogenated amorphous silicon from light-induced effects. Details of the experimental techniques used; Techniques that can be used in determining gap state density; Effect of illumination on the activation energy in hydrogenated amorphous silicon.

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]

Abstract: The modulation of photoluminescence of conducting polymers using Au colloids was studied for poly(3-hexyl thiophene) (P3HT) and poly(2-methoxy-5-(2-ethyl)(hexyloxy) 1,4-phenylenevinylene) (MEHPPV). The extent of modulation can be explained by the extinction of Au colloids and quantum yield of polymer solution. Two types of Au colloids were investigated: nanocluster (∼100nm) and nanoparticles (∼5nm). The addition of the Au nanocluster into either one of the polymer solutions (0.08wt.%) increases the photoluminescence (PL) of each polymer due to the scattering effect from the Au surface plasmon resonance. In contrast, the addition of Au nanoparticle which surface plasmon resonance comes from the absorption component causes a PL quenching. We have observed the PL intensity remains unchanged for P3HT but decreases for MEHPPV. The low quantum yield characteristic of P3HT has stronger polymer interactions than that of MEHPPV, this reduces energy transfer to Au nanoparticles, then dissipates further into heat with no decrease in PL. The polymer interactions are minimized using a dilute polymer solution (1.48×10−5 wt.% for MEHPPV and P3HT respectively). In this case, the nonradiative decay rate of Au colloids becomes dominant, the decrease of PL is observed for both polymers. The photoluminescence of conducting polymer can be modulated by controlling the interactions among polymers and Au colloids. [Copyright &y& Elsevier]

This study presents investigations into the fabrication, characterization, and performance analysis of stretchable white random lasers based on 2D glutamine(GLN)‐functionalized WS2 quantum dots (QDs) enhanced by the integration of Au nanoparticles (NPs) and a wrinkled graphene structure. Wrinkled graphene holds the potential for achieving transient population inversion through electron collisions. Incorporating Au NPs introduces localized surface plasmon resonance (LSPR), which enhances the light‐matter interaction, resulting in reduced lasing thresholds. The GLN‐functionalized WS2 QDs exhibit strong photoluminescence emission, and their integration with a wrinkled graphene structure and Au NPs creates a synergistic effect that enhances the emission efficiency and enables the realization of white random lasing. The extensive characterization and analysis of the emission spectra under different deformation ratios provide valuable insights into the tunability and reliability of these devices, as well as the importance of light trapping due to the wrinkled graphene structure. The findings of this study underscore the significant potential of LSPR and wrinkled graphene structure induced stretchable and white random lasers based on 2D GLN‐functionalized WS2 QDs. These lasers may have a promising application in the field of flexible and wearable photonics, which is a critical step towards the development of next‐generation optoelectronic devices with improved performance. [ABSTRACT FROM AUTHOR]

Nonvolatile memory is an indispensable component of electronic devices. However, the current technology makes it difficult to satisfy the emerging big data demand. To circumvent the existing problems, herein, a first attempt is made to achieve multifunctional nonvolatile memory based on all 2D heterostructures, consisting of histidine‐doped molybdenum disulfide quantum disks mixed with graphene oxide and a graphene macroscopic heterojunction. The designed device possesses intriguing hybrid electrically and optically controllable nonvolatile memory functionalities. By harnessing the unique properties of these materials, memory devices demonstrate long‐term stability and nonvolatile characteristics under both optical and electrical control signals. These devices possess outstanding features, such as multiple read‐write cycles, multi levels, and fast switching speeds, overcoming the limitations of traditional components. To explore the underlying physical mechanism, the Fermi level of graphene is measured and it is confirmed that the charge transfer and trapping across the heterojunctions are the major factors responsible for the observed behavior. This study demonstrates that 2D heterostructures for hybrid optically and electrically controllable nonvolatile memory pave an alternative route for the next‐generation information technology. [ABSTRACT FROM AUTHOR]

Deals with a study which investigated the effect of monochromatic light exposure with different photon energies in order to explore the creation process of optically induced excess conductivity in compensated hydrogenated amorphous silicon films. Methods; Results; Discussion.

Abstract: Nanowire arrays of zinc selenide with zinc blende structures have been synthesized on the zinc foil via a simple thermal evaporation route at relatively low temperature (∼400°C). A self-catalytic liquid–solid growth is proposed for the formation of the nanowires. The nanowires are usually 50–150nm in diameter, and several microns in length. Room-temperature cathodoluminescence spectrum from zinc blende ZnSe nanowires shows a near band edge emission band peaked at around 462nm and a broad deep-level emission band at around 580nm, respectively. [Copyright &y& Elsevier]

The authors provide direct evidence of non-180° domain switching in the piezoelectric response of substrate-free 40 μm thick polycrystalline [Pb(Mg1/3Nb2/3)O3]0.63(PbTiO3)0.37 (PMN-37PT) sheets under dc electric fields through piezoresponse force microscopy (PFM) at the single grain level. The sheet’s polarization preferred pointing in the planar direction which was switched to the normal direction at electric field ranging between 1.3 and 1.9 kV/cm. An independent d31 measurement of PMN-37PT sheets deduced from the axial tip displacement measurements of a 4 mm long PMN-PT/copper cantilever showed enhanced d31 values that peaked at –2700 pm/V in the same range of electric field, consistent with the PFM observation. [ABSTRACT FROM AUTHOR]

Designing a photoredox material with highly efficient organic pollutant degradation ability and cost effectiveness is challenging. Conventional photoredox materials have inherent drawbacks, including high cost, low photon‐to‐electron conversion rates, and low effective surface area. Herein, an alternative nanoporous semiconductor/metal hybrid (CuO‐Ag) photoredox catalysis material with all solution processes is developed to circumvent these shortcomings. The obtained results evidently indicate that the loading of Ag onto the CuO nanoporous material leads to improving the Brunauer–Emmett–Teller (BET) specific surface area (48.369 m2 g−1) with pore size (36.436 nm) and pore's volume (0.301 cm3 g−1) of CuO‐Ag nanoporsity. The improved semiconductor/metal hybrid surface area and porosity significantly enhance the photocatalytic efficiency (i.e., ≈99% degradation of RhB and 4‐NP), owing to the synergy effect. Additionally, the decoration of metal nanostructure enables to enhance photo‐absorption and the semiconductor/metal heterojunction is useful to enhance photo‐excited electron and hole charge carriers separation. Such structure‐designed CuO‐Ag nanoporous materials maintain high photostability during long light irradiation conditions. The photocatalytic efficiency is better than all published reports. This strategy using hybrid semiconductor/metal nanoporous material with high surface area and greater porosity improved activity significantly offers a facile guideline for targeting photoredox catalysis applications. [ABSTRACT FROM AUTHOR]

Hybrid surface wave propagation through the interface of semiconductor and metal waveguides consisting of CuO/Al and ZnO/Al have been investigated by numerical simulation due to their potential applications. COMSOL Multiphysics is used to simulate the waveguides by adjusting model properties. For the comparative study, the propagation constant (γ) , normalized phase (β) , attenuation constant (α) , propagation length (L) , total electric and magnetic energy propagated through the CuO-based Al waveguides and ZnO based Al waveguide is discussed. Comparative studies for both modifications were performed from 0 THz to 12 THz. This study employed boundary conditions to have the continuous behavior of the electric field component of hybrid surface waves (exhibits characteristics of both transverse waves and longitudinal waves) at the interface between metal and semiconductor. The ZnO-based modification shows a higher propagation constant (γ) at all frequencies. Similar trends are observed for propagation length (L) and propagation constant (γ). Meanwhile, the attenuation constant (α) of the CuO-based Al waveguide is higher than that of the ZnO-based Al waveguide. An identical trend was perceived for both electrical and magnetic energy. Maximum parameters favour the ZnO-based Al waveguide, which makes it superior to the CuO-based Al waveguide for high-frequency applications. • Hybrid surface wave propagation along the interface of CuO/Al and ZnO/Al was investigated. • An identical trend was perceived for both electrical and magnetic energy. • Maximum parameters favour the ZnO-based Al waveguide. [ABSTRACT FROM AUTHOR]

It is shown for the first time that hydrogen passivation can be made by using a photochemical vapor deposition system. Unlike the common methods, this new method of hydrogenation has no electron or ion bombardment, thus the sample surface will not be damaged during processing. The effects of hydrogenation are confirmed by the enhancement of photoluminescence intensity. A strong increase in the luminescence intensity (a factor of 23) has been observed which is comparable to the results of rf glow discharge systems. [ABSTRACT FROM AUTHOR]

Converting ambient thermal energy into electricity is of great interest in harvesting energy from the environment. Piezoelectric cantilevers have previously been shown to be an effective biosensor and a tool for elasticity mapping. Here we show that a single piezoelectric (lead-zirconate titanate (PZT)) layer cantilever can be used to convert heat to electricity through pyroelectric effect. Furthermore, piezoelectric-metal (PZT-Ti) bi-layer cantilever showed an enhanced induced voltage over the single PZT layer alone due to the additional piezoelectric effect. This type of device can be a way for converting heat energy into electricity. [ABSTRACT FROM AUTHOR]

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]

This paper presents both an observer/Kalman filter identification (OKID) method-based linear quadratic digital tracker (LQDT) and a new functional observer-based discrete equivalent input disturbance (EID) estimator, for unknown square/non-square singular sampled-data systems with unknown input and output disturbances. Initially, it is shown that even if the solution of the impulsive mode-free singular linear quadratic tracker problem exists, under some quite general conditions the tracker-based generalised algebraic Riccati equation (GARE) might have no solution. To overcome this issue, an innovative methodology that involves an introduced reduced-order equivalent proper regular model (EPRM) of the singular system is presented, to make the tracker-based GARE solvable for a wide class of servo control problems for a singular system. Furthermore, a new functional observer-based design methodology for the discrete EID estimator of the discrete EPRM is proposed in this paper, for a proper sampled-data system with unknown matched/mismatched input and output disturbances. Finally, a discrete-time EPRM of the unknown singular sampled-data system is constructed using the off-line OKID method and the robust prediction-based state-estimate optimal LQDT, associated with the (plug-in) discrete EID estimator, is developed for the singular sampled-data system. [ABSTRACT FROM AUTHOR]

Reports on the photoconduction of synthetic pyrite FeS[sub2] single crystals with low impurity concentration prepared by chemical vapor transport. Experimental details; Results and discussions.

Presents a study which evaluated the morphologies and photoluminescence of porous silicon under different etching and oxidation conditions. Details on the experiment; Results of the study; Discussion of findings.

Indium selenide (InSe) is an emerging van der Waals material, which exhibits the potential to serve in excellent electronic and optoelectronic devices. One of the advantages of layered materials is their application to flexible devices. How strain alters the electronic and optical properties is, thus, an important issue. In this work, we experimentally measured the strain dependence on the angle-resolved second harmonic generation (SHG) pattern of a few layers of InSe. We used the exfoliation method to fabricate InSe flakes and measured the SHG images of the flakes with different azimuthal angles. We found the SHG intensity of InSe decreased, while the compressive strain increased. Through first–principles electronic structure calculations, we investigated the strain dependence on SHG susceptibilities and the corresponding angle-resolved SHG pattern. The experimental data could be fitted well by the calculated results using only a fitting parameter. The demonstrated method based on first–principles in this work can be used to quantitatively model the strain-induced angle-resolved SHG patterns in 2D materials. Our obtained results are very useful for the exploration of the physical properties of flexible devices based on 2D materials. [ABSTRACT FROM AUTHOR]

Light-induced metastable defects in hydrogenated amorphous silicon can be eliminated by atomic hydrogen at the temperature below which the annealing effect occurs. The resulting material has a very high photosensitivity and stability. [ABSTRACT FROM AUTHOR]

The x-type hexaferrites have been getting considerable attention owing to their promising application in electronic fields. Though, the growth of nanosized crystal X-type hexagonal ferrites is still a big challenge. Herein, the synthesis of nanosized X-type hexagonal ferrites Ca 2 Co 2−x Zn x Fe 28 O 46 (X = 0.0, 0.4, 0.8, 1.2, 1.6, and 2.0) with high quality is reported using the auto-combustion sol-gel method. The objective of the study was to improve the structural and dielectric properties of X-type hexagonal ferrite which was achieved through variation of concentration of cobalt and zinc. Structural, morphological, and dielectric properties were investigated. X-ray diffraction (XRD) patterns confirmed the single-phase x-type hexagonal structure. The crystal size of all samples was in the range of 22.7–23.8 nm. Other parameters such as d -spacing, lattice parameters, unit cell volume, dislocation density, atomic packing fraction, degree of crystal lattice distortion, number of the unit cells, and volume of particles were also calculated. Fourier transform infrared spectroscopy (FTIR) confirmed the formation of metal oxide bonds with two absorption bands at 574 cm−1 and 424 cm−1. The morphology of the prepared Ca 2 Co 2−x Zn x Fe 28 O 46 with the variation of Co and Zn was examined by scanning electron microscopy. Increasing crystallinity and agglomeration were observed with the upsurge in Zn and Co. The dielectric properties of Ca 2 Co 2−x Zn x Fe 28 O 46 with the variation of Zn and Co revealed that these materials might be considered good candidates for modern devices. [Display omitted] • Nanosized X-type hexagonal ferrites was synthesized by auto-combustion sol-gel. • Crystal size of all samples was in the range of 22.7–23.8 nm. • Dielectric properties revealed that materials are good candidate for devices. [ABSTRACT FROM AUTHOR]

The first electrically driven random laser diode with nonvolatile resistive random access memory functionality is designed and demonstrated. To illustrate the working principle, a metal-insulator-semiconductor structure based on Pt/MgO/ZnO thin-film layers is fabricated on indium tin oxide glass. The current-voltage curve of the dual-function random laser memory (RLM) device exhibits an excellent electrical bistability with a high ON/OFF current ratio (≈107). The random lasing behavior is simultaneously demonstrated by using electrical pumping with the appearance of sharp-peak emissions and a drastic enhancement of peak intensity. A wide angle-dependent electroluminescence not only reveals its emitting advantage but also further supports the origin of random lasers. The first proof-of-concept presentation of RLM possesses several advantages of dual memory and lasing functions, which enables to open up new avenues to practical applications, such as light emitting memories for electrical and optical communication. This new horizon for the realization of all optical memories should therefore be able to attract academic as well as industrial interests. It is stressed here that the electrical reading of conventional memory array is usually in serial sequence, which limits the maximum data throughput. This hurdle can be overcome by optically readable memory devices. [ABSTRACT FROM AUTHOR]

To create a sensitive photodetector, the transparent and conductive properties of graphene and the optical and photovoltaic properties of poly(3-hexylthiophene) (P3HT) are combined as a hybrid composite. Based on the inherent nature of the band alignment between graphene and P3HT, the photogenerated holes are able to transfer to the graphene layer and improve the photoresponse to be much better than the traditional layer by layer organic system. Additionally, the graphene is deposited on a piezoelectric Pb(Zr0.2Ti0.8)O3 (PZT) substrate, and the photoresponse of such composite photodetectors is found to be ten times larger than on SiO2 base. It is demonstrated that the electric field of the polarization of piezoelectric substrate helps the spatial separation of photogenerated electrons and holes and promotes the hole doping of graphene to enhance the photoconduction. A detailed investigation of graphene layers, thickness of P3HT and time evolution shows that the composite of graphene and P3HT on PZT can be used as a sensitive photodetector and has potential as an effective solar cell. Moreover, with the replacement of P3HT by a thin layer of bulk heterojunction of polymer and fullerene, the photosensitivity can be further increased by more than one order of magnitude. [ABSTRACT FROM AUTHOR]

Abstract: Interface control is an important issue in polymer based solar cells because the influence of interface property on bulk heterojunction transport can govern the device performance. We systematically select a series of thioaromatic molecules to tune the surface characters of the metal-oxide array in inverted ZnO-nanorod/poly(3-hexythiophene):(6,6)-phenyl C61 butyric acid methyl ester (P3HT:PCBM)/Ag devices. In addition to physically improving the compatibility between ZnO-nanorod and polymer blend contact junction, those conjugated thioaromatic molecules slightly modulate the nanostructured donor and acceptor percolated networks as revealed by the measured carrier mobility values whereas the modulations of photon absorption efficiency and the exciton dissociation rate are negligible. The balanced charge transport architecture can be obtained by using longer and linearly arranged aromatic rings. Additionally, both series resistance and shunt resistance are also improved. As high as ~80% enhancement in power conversion efficiency of the device has been achieved. The result decouples the contribution of the exciton dissociation rate from the bulk heterojunction charge transport process to device performance in inverted polymer solar cells and can be generalized to hybrid polymer-nanocrystal systems as well. [Copyright &y& Elsevier]

Abstract: We report a simple fabrication process for the growth of nanotip-decorated ZnO nanobottles with an enhanced field emission property. Well-aligned ZnO nanobottles grown on ITO-coated glass substrates were synthesized by the thermal evaporation technique with the up-side down arrangement of substrate compared with the common method. The hydrothermal growth was carried out to decorate the nanobottles with ZnO nanotips. We demonstrate that the nanobottles decorated with nanotips show a much better field emission property. The improved field emission is attributed to the different local field enhancement factors at the nanobottles tops. Our results confirm the importance of the top morphology of a material in field emission. [Copyright &y& Elsevier]

Abstract: A simple two-step approach to produce highly ordered ZnO nanotube arrays is introduced. In the first step, Zn nanotubes were prepared by the electrodeposition of Zn into the pores of anodic alumina membrane (AAM), and then they were oxidized in air and converted into ZnO nanotubes. This approach is very simple, molecular anchor free, and is capable of growing ZnO nanotubes at low temperature. The ZnO nanotubes synthesized by this method exhibit an intense and sharp cathodoluminescence at 378nm and a weak defect emission at about 500nm at room temperature, indicating good quality of the prepared samples. Our approach is very general, which provides an alternative method for preparing highly ordered metal oxide nanotube arrays with good quality at relatively low temperatures. [Copyright &y& Elsevier]

Abstract: We report the successful synthesis of metal (Zn, Sn) nanotube arrays and metal (Cu, Ag) nanotube/nanowire junction arrays electrochemically deposited through nanoporous anodic alumina membranes. The metal (Zn, Sn) nanotube arrays were achieved by preferentially plating at circular step edges of the Au nanorings with hydrogen gas generation, critical to the evolution of tube formation. Quite interestingly, if there is no hydrogen gas generation, the metal (Cu, Ag) nanotube/nanowire junction arrays were obtained. This approach is very simple, molecular anchor free, and is generally capable of growing other metal nanotube arrays and nanotube/nanowire junction arrays. [Copyright &y& Elsevier]

Recent advancements in isolation and stacking of layered van der Waals materials have created an unprecedented paradigm for demonstrating varieties of 2D quantum materials. Rationally designed van der Waals heterostructures composed of monolayer transition‐metal dichalcogenides (TMDs) and few‐layer hBN show several unique optoelectronic features driven by correlations. However, entangled superradiant excitonic species in such systems have not been observed before. In this report, it is demonstrated that strong suppression of phonon population at low temperature results in a formation of a coherent excitonic‐dipoles ensemble in the heterostructure, and the collective oscillation of those dipoles stimulates a robust phase synchronized ultra‐narrow band superradiant emission even at extremely low pumping intensity. Such emitters are in high demand for a multitude of applications, including fundamental research on many‐body correlations and other state‐of‐the‐art technologies. This timely demonstration paves the way for further exploration of ultralow‐threshold quantum‐emitting devices with unmatched design freedom and spectral tunability. [ABSTRACT FROM AUTHOR]

Crystallinity and crystal orientation have a predominant impact on a materials' semiconducting properties, thus it is essential to manipulate the microstructure arrangements for desired semiconducting device performance. Here, ultra‐uniform hole‐transporting material (HTM) by self‐assembling COOH‐functionalized P3HT (P3HT‐COOH) is fabricated, on which near single crystal quality perovskite thin film can be grown. In particular, the self‐assembly approach facilitates the P3HT‐COOH molecules to form an ordered and homogeneous monolayer on top of the indium tin oxide (ITO) electrode facilitate the perovskite crystalline film growth with high quality and preferred orientations. After detailed spectroscopy and device characterizations, it is found that the carboxylic acid anchoring groups can down‐shift the work function and passivate the ITO surface, retarding the interface carrier recombination. As a result, the device made with the self‐assembled HTM show high open‐circuit voltage over 1.10 V and extend the lifetime over 4,300 h when storing at 30% relative humidity. Moreover, the cell works efficiently under much reduced light power, making it useful as power source under dim‐light conditions. The demonstration suggests a new facile way of fabricating monolayer HTM for high efficiency perovskite devices, as well as the interconnecting layer needed for tandem cell. [ABSTRACT FROM AUTHOR]

Despite being one of the most robust materials with intriguing optoelectronic properties, the practical use of single‐layer graphene (SLG) in soft‐electronic technologies is limited due to its poor native stretchability, low absorption coefficient, poor on/off ratio, etc. To circumvent these difficulties, here, a rippled gate‐tunable ultrahigh responsivity nanostack phototransistor composed of SLG, semiconductor‐nanoparticles (NPs), and metallic‐nanowires (NWs) embedded in an elastic film is proposed. The unique electronic conductivity of SLG and high absorption strength of semiconductor‐NPs produce an ultrahigh photocurrent gain. The metallic NWs serve as an excellent stretchable gate electrode. The ripple structured nanomaterials surmount their native stretchability, providing strength and electromechanical stability to the composite. Combining all these unique features, highly stretchable and ultrasensitive phototransistors are created, which can be stretched up to 30% with high repeatability maintaining a photoresponsivity, photocurrent gain, and detectivity of ≈106 A W−1, 107, and 1013 Jones, respectively, which are comparable with the same class of rigid devices. In addition, the device can be turned‐off by applying a suitable gate voltage, which is very convenient for photonic circuits. Moreover, the study can be extended to many other 2D systems, and therefore paves a crucial step for designing high‐performance soft optoelectronic devices for practical applications. [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]

The development of two‐dimensional (2D) materials has brought the breakthrough for scientific discoveries and widespread applications in many emerging devices. However, the related study on lasers is rather limited. In this study, a stretchable and broadband cavity‐free laser device based on all 2D metamaterials consisting of molybdenum disulfide (MoS2)/graphene nanocomposites is designed and demonstrated. When the pumping power density of the device is more than 200 W cm−2, multiple pronounced narrow peaks with linewidth <0.5 nm superimpose on the spectra, providing the signature for laser actions. The optical properties of MoS2/graphene meta‐nanocomposites for MoS2 quantum dots (QDs) with different concentration of l‐histidine doping are also examined. It is emphasized that under optimized doping concentration of MoS2 QDs, the laser action of the device can be effectively enhanced. Furthermore, it is shown that the laser action of the devices is controllable by applying an external strain. It is demonstrated that after stretching for more than 200 times, the performance still remains the same with negligible change, indicating the robustness of the device. The presented stretchable laser devices based on all 2D meta‐nanocomposites therefore can open new possibilities for future developments of not‐yet realized optoelectronic devices. [ABSTRACT FROM AUTHOR]

The ultraviolet (UV) electroluminescence (EL) from the TiO2/ZnO coaxial nanowires (NWs)/poly(3,4-ethylenedioxythiophene)-poly(styrene-sulfonate) inorganic/organic heterostructure devices is greatly enhanced and the defect emission is significantly suppressed compared with the uncoated ZnO NW device at room temperature. The origins of the great changes in EL of ZnO NW devices are attributed to the surface modification of the sputtered TiO2 coating and the reduction in the pinhole traps on the surface of ZnO NWs. It is found that for the optimized device, the EL intensity ratio between the band gap and defect emission can be greatly enhanced by up to about 250 times its prior level. Such ZnO NW devices with enhanced UV emission have potential applications in the highly efficient solid state emitters. [ABSTRACT FROM AUTHOR]

A thermal emitter with selective wavelength has been demonstrated in which the dielectric layers formed one-dimensional photonic crystals are sandwiched between two Ag films. The top Ag film is perforated periodically with hexagonal hole array. The selected thermal radiation of the photonic crystals resonates between two metal films and surface plasmon polaritons are generated on the top Ag and converted to light radiation. It is found that when leakage modes adjacent to the optic band gap of photonic crystals meet the resonant modes of surface plasmom polaritons, an enhanced thermal emission with maximum intensity can be obtained. The hybrid photonic and plasmonic thermal emitters are selective, which should be very useful for the creation of high power infrared light sources. [ABSTRACT FROM AUTHOR]

It is demonstrated that magnetic periodic arrays can be easily fabricated from direct writing water developable La0.7Sr0.3MnO3 electron beam resist. Two unique features of our approach are (1) the patterned La0.7Sr0.3MnO3 resist film can be developed using nontoxic and environmentally friendly pure water and (2) either positive or negative patterns can be fabricated depending on the dosage of electron beam. The mechanism of the dual function characteristic of the resist was studied using Kelvin probe microscope. The surface potential of patterned La0.7Sr0.3MnO3 resist increases with increasing electron beam dosage due to the changes of resist composition. The formations of periodic magnetic arrays were confirmed by the studies of scanning electron microscope and magnetic force microscope. The magnetization of La0.7Sr0.3MnO3 can be enhanced by postsintering the sample at 900 °C after electron beam irradiation. We have therefore provided a one-step, simple, and convenient alternative technique for the fabrication of nanoscale magnetic patterns, which form the building blocks for the study of physical properties in periodic magnetic arrays. [ABSTRACT FROM AUTHOR]

Room-temperature visible lasing in CdSe semiconductor nanotube arrays embedded in anodic aluminum oxide template has been demonstrated. The cylindrical nanocavities of anodic aluminum oxide template form laser resonators, and the laser oscillation was achieved through whispering gallery mode gain from the interior semiconductor nanotubes. The linearly polarized stimulated emission, the one dimensionality, and the chemical accessibility to nanotubes render them significant potential for serving as various applications in optoelectronic devices. [ABSTRACT FROM AUTHOR]

An organic two-terminal phototransistor structure for information technology has been designed, fabricated, and demonstrated. The device comprises a resistive random access memory (RRAM) in tandem with an organic solar cell (OSC). The transistor effect is realized by the functional integration of both individual devices; i.e., the photocurrent produced by the OSC is manipulated through the switchable RRAM. Compared with conventional phototransistors, our design possesses several intriguing features, including ultra-fast photoresponse time, controllable photocurrent, and solution processable active layers. Most importantly, these operational properties are achievable with only two vertically sandwiched electrodes, which are beneficial for high speed optical communication, circuit miniaturization, and energy saving. These unique features make it a good candidate for implementation in optical communication with diverse applications such as Li-Fi technology and security encryption. [ABSTRACT FROM AUTHOR]

Abstract Towards the sustainable development, optoelectronic devices with biodegradability and biocompatibility have been a desirable but challenging issue for years. In this study, an all-biomaterial random laser device based on all-marine elements has been demonstrated. Chlorophyll and blue coral skeletons serve as gain medium and scattering centers, respectively. The chlorophyll is derived from marine diatoms, which are ubiquitous in the ocean and set up an abundant source for the device. On the other hand, the coral skeletons with intrinsic nanorod structures can provide a strong optical confinement and feedback for laser action. The proposed design signifies the novel application of marine materials and represents a significant step for the development of bio-inspired photonics modules. Graphical abstract Image 1 Highlights • The first all-marine based random laser with biocompatibility is demonstrated. • Selecting the extracted diatoms is not only because of their excellent luminescent capability, but also their non-toxicity. • Blue coral skeletons are a reusable material because of its robust nature, which enables to sustain the harsh environment. • Owing to the randomly distributed architectures of the coral skeleton, the light can be easily scattered for laser action. [ABSTRACT FROM AUTHOR]

Abstract: Application of lasers is omnipresent in modern‐day technology. However, preparation of a lasing device usually requires sophisticated design of the materials and is costly, which may limit the suitable choice of materials and the lasing wavelengths. Random lasers, on the other hand, can circumvent the aforementioned shortcomings with simpler fabrication process, lower processing cost, material flexibility for any lasing wavelengths with lower lasing threshold, providing a roadmap for the design of super‐bright lighting, displays, Li‐Fi, etc. In this work, ultralow‐threshold random laser action from semiconductor nanoparticles assisted by a highly porous vertical‐graphene‐nanowalls (GNWs) network is demonstrated. The GNWs embedded by the nanomaterials produce a suitable cavity for trapping the optical photons with semiconductor nanomaterials acting as the gain medium. The observed laser action shows ultralow values of threshold energy density ≈10 nJ cm−2 due to the strong photon trapping within the GNWs. The threshold pump fluence can be further lowered to ≈1 nJ cm−2 by coating Ag/SiO2 upon the GNWs due to the combined effect of photon trapping and strong plasmonic enhancement. In view of the growing demand of functional materials and novel technologies, this work provides an important step toward realization of high‐performance optoelectronic devices. [ABSTRACT FROM AUTHOR]

Presents a study that investigated the material properties of In[subx]Ga[sub1-x]As epilayers on gallium arsenide by molecular-beam epitaxy. Interpretation of the cross-sectional transmission electron microscopy images for the heterojunctions; Relation used to estimate the upper limit of threading dislocation density in terms of the full width at half-maximum of the (400) double-crystal x-ray diffraction signal; Analysis of the magnetophotoconductivity signals.

Based on the concept of optical enhancement in nanoparticle-mediated coupling, a novel composite consisting of ZnO nanorods and ZnO nanoparticles has been synthesized and characterized. The ZnO nanoparticles can be regarded as light-coupling media to increase the absorption cross section of excitation light as well as the emission extraction efficiency due to the relaxation of momentum selection rule. With our devised ZnO nanostructures, the band gap emission of ZnO nanorods can be enhanced by up to 8.5 times. The strategy of optical enhancement provided here should be very useful in designing many other nanostructures for high efficiency optoelectronic devices. [ABSTRACT FROM AUTHOR]

The femtosecond pulsed Z-scan measurements of the resonant nonlinear optical absorption of the InN epitaxial films in the range of 720–790 nm were reported. The absorption saturation behavior was found to gradually decrease with increasing photon energy. The nonlinear optical absorption cross sections of the InN films were estimated and the values are found to be in good agreement with the calculations based on the band-filling model. These results are relevant for the future development of nonlinear optical devices based on InN. [ABSTRACT FROM AUTHOR]

Abstract: Toward practical applications of random lasers, controllability is a key factor. Here, magnetically controllable random lasers (MCRLs) are designed, fabricated, and demonstrated. Under a prescribed magnetic field, the MCRLs composed of stilbene 420 laser dye, TiO2 nanoparticles, and Fe3O4 nanoparticles possess magnetic controllability and switchability with good responsivity and durability. The applied magnetic field can be used to manipulate the distribution of Fe3O4 nanoparticles, which in turn alters the formation of the coherent loops and the properties of laser action. The MCRLs developed here can serve as magneto‐optics prototypes for several potential applications, such as biomedicine and optical communications. [ABSTRACT FROM AUTHOR]

A solution-processable planar perylene diimide, N , N ´-dipentyl-3,4,9,10-perylenedicarboximide (PDI), has been demonstrated as a suitable acceptor material to replace the conventional fullerene derivatives (e.g., PCBM) found in inverted perovskite solar cells (PSCs). The energy offset between the perovskite and PDI layers was optimized by varying the ratio of halides (iodide to bromide) to improve the exciton dissociation and carrier transport. The PDI acceptor material had higher electron mobility and smoother morphology on perovskite relative to those of PCBM, leading to enhancements in the short circuit current density, fill factor, and power conversion efficiency. The incorporation of PDI in the perovskite devices decreased recombination losses and improved the device stability. The performance of the best PSC containing PDI as the electron transport layer (11%) was higher than that of the best device featuring PCBM (10%). [ABSTRACT FROM AUTHOR]

Phase-change memory materials such as the pseudobinary GeTe-Sb2Te3 compounds have recently gained attention for their good thermoelectric properties, which can be used for power-generation/cooling applications. In this work, GeTe-rich Ge-Sb-Te thin films deposited using a radio-frequency magnetron sputtering method readily exhibit the metastable face-centered cubic (FCC) phase at room temperature. This is in stark contrast to its bulk form, which only transforms to its FCC phase after a transition temperature of around 350 °C. Based on previous works, the FCC phase contributes to the superior thermoelectric properties of this material system. In this study, by decreasing the working deposition pressure, the preferred orientation of (200) plane is observed that translates to improved carrier mobility. Moreover, increasing the annealing temperature has been shown to decrease the carrier concentration due to Te deficiency, leading to a significant improvement in the Seebeck coefficient of the film. By combining these effects, an optimized thermoelectric power factor (21 μW/cm K2) was obtained at an operating temperature of 350 °C. [ABSTRACT FROM AUTHOR]

2D ternary semiconductor single crystals, an emerging class of new materials, have attracted significant interest recently owing to their great potential for academic interest and practical application. In addition to other types of metal dichalcogenides, 2D tin dichalcogenides are also important layered compounds with similar capabilities. Yet, multi-elemental single crystals enable to assist multiple degrees of freedom for dominant physical properties via ratio alteration. This study reports the growth of single crystals Se-doped SnS2 or SnSSe alloys, and demonstrates their capability for the fabrication of phototransistors with high performance. Based on exfoliation from bulk high quality single crystals, this study establishes the characteristics of few-layered SnSSe in structural, optical, and electrical properties. Moreover, few-layered SnSSe phototransistors are fabricated on both rigid (SiO2/Si) and versatile polyethylene terephthalate substrates and their optoelectronic properties are examined. SnSSe as a phototransistor is demonstrated to exhibit a high photoresponsivity of about 6000 A W−1 with ultra-high photogain [ABSTRACT FROM AUTHOR]

Electronic skin sensing devices are an emerging technology and have substantial demand in vast practical fields including wearable sensing, robotics, and user-interactive interfaces. In order to imitate or even outperform the capabilities of natural skin, the keen exploration of materials, device structures, and new functions is desired. However, the very high resistance and the inadequate current switching and sensitivity of reported electronic skins hinder to further develop and explore the promising uses of the emerging sensing devices. Here, a novel resistive cloth-based skin-like sensor device is reported that possesses unprecedented features including ultrahigh current-switching behavior of ≈107 and giant high sensitivity of 1.04 × 104-6.57 × 106 kPa−1 in a low-pressure region of <3 kPa. Notably, both superior features can be achieved by a very low working voltage of 0.1 V. Taking these remarkable traits, the device not only exhibits excellent sensing abilities to various mechanical forces, meeting various applications required for skin-like sensors, but also demonstrates a unique competence to facile integration with other functional devices for various purposes with ultrasensitive capabilities. Therefore, the new methodologies presented here enable to greatly enlarge and advance the development of versatile electronic skin applications. [ABSTRACT FROM AUTHOR]

Hybrid quantum dot-graphene photodetectors have recently attracted substantial interest because of their remarkable performance and low power consumption. However, the performance of the device greatly depends on the interfacial states and photogenerated screening field. As a consequence, the sensitivity is limited and the response time is relatively slow. In order to circumvent these challenges, herein, a composite graphene and graphene quantum dot (GQD) photodetector on lead zirconate titanate (Pb(Zr0.2Ti0.8)O3) (PZT) substrates has been designed to form an ultrasensitive photodetector over a wide range of illumination power. Under 325 nm UV light illumination, the device shows sensitivity as high as 4.06 × 109 A W−1, which is 120 times higher than reported sensitivity of the same class of devices. Plant derived GQD has a broad range of absorptivity and is an excellent candidate for harvesting photons generating electron-hole pairs. Intrinsic electric field from PZT substrate separates photogenerated electron-hole pairs as well as provides the built-in electric field that causes the holes to transfer to the underlying graphene channel. The composite structure of graphene and GQD on PZT substrate therefore produces a simple, stable, and highly sensitive photodetector over a wide range of power with short response time, which shows a way to obtain high-performance optoelectronic devices. [ABSTRACT FROM AUTHOR]

In this study, we theoretically and experimentally demonstrate high performance of antireflection (AR) coating composed of the ZnO nanorods (NRs) and TiO 2 layers applied on InGaP/GaAs/Ge triple-junction solar cells. The high performance of this AR coating is due to the realization of a smooth gradient profile of refractive index fabricated by only two physical layers. First, due to the inherent inhomogeneous-nanoporous geometry along the surface normal, the ZnO NRs are reasonable to be considered as discrete multiple optical layers with low scattering loss, leading to the index smoothly increasing from air ambient toward down to the solar cells. Second, to compensate the gap of index between ZnO and solar cells, an additional TiO 2 layer with index in between is hence necessary to insert under ZnO NRs, significantly further reducing the Fresnel reflection loss of the entire device. The ZnO NRs/ TiO 2 layer shows a low wavelength-averaged (solar spectrum weighted) reflectance of 6.00% (4.78%) over a wide spectral range of λ =380–1800 nm, and exhibits a hydrophobic surface with a water contact angle of 128.2°. At device level, we compared the photovoltaic performance of solar cells with and without AR coating, the short-circuit density ( J SC ) is enhanced by 31.8% and 23.8% for solar cells integrated with the ZnO NRs/TiO 2 layer and conventional SiO 2 /TiO 2 double-layer AR (DLAR) coating, respectively. Under a very large incident angle of solar illumination ( θ =80°), the ZnO NRs/TiO 2 layer remains static with J SC enhancement of 35.2%, whereas the J SC enhancement of conventional DLAR coating drops down to 9.4%. In addition, the ZnO NRs/TiO 2 layer barely affects the open-circuit voltage and fill factor of the solar device. Therefore, the proposed ZnO NRs/TiO 2 layer with a smoother graded refractive index change is highly promising for the AR coating applications for the next-generation solar cells. [ABSTRACT FROM AUTHOR]