Transparent Indium Tin Oxide Electrodes Research Articles

Analysis of continuous laser-irradiation resistance of liquid-crystal optical switch based on sapphire-substrate GaN

Developing high-power laser technology and its applications necessitates improvements in the laser-irradiation resistance of liquid-crystal modulation devices. In this study, the thermal characteristics of substrate and electrode materials, including sapphire-substrate indium tin oxide (ITO) electrodes, K9 glass-substrate ITO electrodes, sapphire-substrate gallium nitride (GaN) electrodes, and liquid-crystal optical switches, are investigated using simulation and experimental methods. Results show that the sapphire-substrate GaN electrode demonstrates the best heat dissipation and that the maximum temperature at the center of the spot under 75 W laser irradiation is 319 K, 52 K lower than that of an equally thick sapphire-substrate ITO electrode and 225 K lower than that of an equally thick K9 glass-substrate ITO electrode (steady state and test time >2min). Additionally, the experimental results show that the liquid-crystal optical switch, comprising a sapphire substrate and GaN electrode, can endure continuous laser irradiation up to 18 W with a switching ratio of approximately 20:1. The optical switch with GaN electrodes on a sapphire substrate can endure a power density of 156W/cm2, much higher than that (21W/cm2, steady state and test time >2min) tolerable by the liquid-crystal optical switch with ITO transparent electrodes and K9 glass substrates.

Assessing the Influence of Confinement on the Stability of Polyoxometalate-Functionalized Surfaces: A Soft Sequential Immobilization Approach for Electrochromic Devices.

A functionalization process has been developed and the experimental conditions optimized allowing the immobilization of first-row transition metal (Mn+) containing polyoxometalates (POMs) with the formula [M(H2O)P2W17O61](10-n)- on transparent indium-tin oxide (ITO) electrodes for electrochromic applications. Both flat ITO grafted with 4-sulfophenyl moieties and sulfonate-functionalized vertically oriented silica films on ITO have been used as electrode supports to evaluate possible confinement effects provided by the mesoporous matrix on the stability of the modified surfaces and their electrochromic properties. Functionalization involved a two-step sequential process: (i) the immobilization of hexaaqua metallic ions, such as Fe(H2O)63+, onto the sulfonate-functionalized materials achieved through hydrogen bonding interactions between the sulfonate functions and aqua ligands (water molecules) coordinated to the metallic ions facilitating and stabilizing the attachment of the metallic ions to the sulfonated surfaces; (ii) their coordination to [P2W17O61]10- species to generate "in situ" the target [Fe(H2O)P2W17O61]7- moieties. Comparison of the characterized surfaces clearly evidenced a significant improvement in the long-term stability of the nanostructured [Fe(H2O)P2W17O61]7--functionalized silica films compared to the less constrained flat [Fe(H2O)P2W17O61]7--modified ITO electrodes for which a rapid loss of [P2W17O61]10- species was observed. Concordantly, the [Fe(H2O)P2W17O61]7- POM confined in the mesoporous films coated on ITO gave rise to much better and stable electrochromic properties, with a transmittance modulation of 40% at 515 nm.

High‐Performance Fully Transparent Ultraviolet Photodetector Fabricated Using GaN‐Based Schottky Barrier Photodiode

Transparent electronics is a burgeoning field with exciting potential for next‐generation “see‐through” devices. The creation of high‐performance fully transparent ultraviolet photodetectors (PDs) is essential for enabling wearable and portable applications. In this study, metal–semiconductor–metal (MSM) type Al‐doped ZnO (AZO)/GaN/AZO and indium tin oxide (ITO)/GaN/ITO‐transparent ultraviolet PDs, are initially designed, utilizing AZO‐ and ITO‐transparent conductive electrodes. In these investigations, it is revealed that AZO and ITO form Ohmic and Schottky contacts, respectively, with GaN. Subsequently, building on these findings, a fully transparent Schottky barrier photodiode (SBPD) is developed for ultraviolet photodetection using AZO/GaN/ITO. The SBPD displays a high responsivity (R) of 1.41 × 103 A W−1, a detectivity (D*) of 6.85 × 1014 Jones, and a photo‐to‐dark current ratio exceeding 1 × 104 at a − 5 V bias. Furthermore, the SBPD demonstrates an ultrahigh responsivity of 1.18 A W−1 at 0 V bias, indicating its potential as a self‐powered device under extreme conditions. In these results, the tremendous potential of the high‐performance and fully transparent GaN‐based SBPD is demonstrated for environmental monitoring, optical communication, military radar, and other fields.

Optical Read‐Out of the Electrical Switching of Cobalt‐Terpyridine‐BODIPY Molecules Immobilized as Single Layer on ITO

AbstractA single layer of a dyad made of a cobalt(II) bis‐terpyridine complex functionalized with a Boron‐dipyrromethene (BODIPY) fluorophore on transparent Indium Tin Oxide (ITO) electrode is prepared. A modulation of the photoluminescence intensity of the fluorophore upon the application of an electric stimulus on the ITO electrode that supports 10 picomoles of molecules is demonstrated. The intensity of the fluorescence intensity decreases when the cobalt is at the oxidation state +III, due to CoIII oxidative quenching of BODIPY emission that has a higher driving force than the CoII reductive quenching initially responsible for the low fluorescence intensity of the chemisorbed dyad.

In situ observation of indium filament growth dynamics in ITO electrode-based memristor

Indium tin oxide (ITO) electrode is commonly used in integrated transparent electronics, including memristor, solar cell, light emitting diode, and photodetector. However, the lack of appropriate understanding of indium (In) ions motion from ITO is the major roadblock to disclose the mechanism of ITO electrode-based memristors. Revealing the filaments growth dynamics is of critical importance to continued devices optimization. Here, we show direct evidence of In filament growth dynamics by in situ transmission electron microscopy, where the In–O bond in ITO would dissociate at high electric field, leading to the In ions transport and cone-like filament formation in the dielectric layer. The In filament formation and melt are responsible for the resistive switching, which can both commence growth toward active ITO and inert Au electrodes, respectively, by controlling the ion mobility. This study can provide a generalized guideline for high performance electronics design and modeling with transparent ITO electrodes.

Recent progress in dielectric/metal/dielectric electrodes for foldable light-emitting devices

Abstract Flexible optoelectronic devices have a broad application prospect in the field of wearable electronic devices, among which the superior transparent electrode is the core problem in achieving high-performance flexible optoelectronic devices. The brittle indium tin oxide (ITO) transparent electrode, which is currently commonly used, is difficult to be compatible with the flexible substrate. Multilayer dielectric/metal/dielectric (DMD) structure films are attracting attention as next-generation ITO-free electrodes. High optical transmittance, super electrical conductivity, and mechanical flexibility of DMD electrodes make them promising for highly efficient optoelectronic devices. Despite substantial research on the optimization of DMD electrodes, a large gulf still exists in obtaining foldable and transparent conductive electrodes and applying them to light-emitting devices, including organic light-emitting diodes (LEDs), quantum dot LEDs, and perovskite LEDs. In this perspective, we review the superiority of DMD electrodes in terms of optical and electrical performance, and mechanical flexibility, and summarize their applications in LEDs. Furthermore, we also give future research directions for DMD electrodes regarding physical properties, mechanism stability, and application reliability.

Oxidative Stress Sensing System for 8-OHdG Detection Based on Plasma Coupled Electrochemistry by Transparent ITO/AuNTAs/PtNPs Electrode.

8-Hydroxydeoxyguanosine (8-OHdG) is the most widely used oxidative stress biomarker of the free radical-induced oxidative damage product of DNA, which may allow a premature assessment of various diseases. This paper designs a label-free, portable biosensor device to directly detect 8-OHdG by plasma-coupled electrochemistry on a transparent and conductive indium tin oxide (ITO) electrode. We reported a flexible printed ITO electrode made from particle-free silver and carbon inks. After inkjet printing, the working electrode was sequentially assembled by gold nanotriangles (AuNTAs) and platinum nanoparticles (PtNPs). This nanomaterial-modified portable biosensor showed excellent electrochemical performance for 8-OHdG detection from 10 μg/mL to 100 μg/mL by our self-developed constant voltage source integrated circuit system. This work demonstrated a portable biosensor for simultaneously integrating nanostructure, electroconductivity, and biocompatibility to construct advanced biosensors for oxidative damage biomarkers. The proposed nanomaterial-modified ITO-based electrochemical portable device was a potential biosensor to approach 8-OHdG point-of-care testing (POCT) in various biological fluid samples, such as saliva and urine samples.

Zinc oxide and indium tin oxide as embedding layers for ultrathin-silver-based transparent electrodes: A comparative study

The triple-layered structure comprising an ultrathin (∼10 nm) Ag layer embedded between two dielectric layers exhibits high visible light transmittance, electrical conductivity, and flexibility, and this triple-layered structure is thus considered as a promising candidate to replace the conventional single-layered indium tin oxide (ITO) transparent conductive electrodes in optoelectronic devices. While various dielectrics have been employed for the underlayer and overlayer, ITO and zinc oxide (ZnO) are the two common choices. In this study, we investigated the structural, electrical, optical, and thermal properties of triple-layered electrodes (dielectric underlayer/Ag/dielectric overlayer) comprising Ag, ZnO, and ITO; namely, ZnO/Ag/ZnO, ZnO/Ag/ITO, ITO/Ag/ITO, and ITO/Ag/ZnO electrodes, in which all layers were sputter-deposited at 293 K. The deposition of crystalline Ag onto crystalline ZnO and amorphous ITO surfaces exhibited distinctly dissimilar Ag nucleation dynamics, resulting in significant differences in the structural and thus electrical characteristics prior to Ag-layer-closure. After the formation of continuous Ag layers, the electrical conductivities became similar, whereas the optimized ITO/Ag/ZnO structure exhibited a considerably higher visible light transmittance than the other electrodes (with an average transmittance of 92.8%). Further, we found that the ZnO/Ag interface stability was significantly higher than that of the ITO/Ag interface during an electrically driven Joule heating process.

Fully-transparent self-powered ultraviolet photodetector based on GaOx/ZnO heterojunction for solar-blind imaging

With the development of fully-transparent electronic materials and energy-efficient photodetectors, self-powered deep-ultraviolet photodetectors that are fully transparent are expected to have a wide range of applications in solar-blind imaging. Here, we present the first investigation of a self-powered, fully transparent Ga2O3 deep-ultraviolet photodetector array for solar-blind imaging. The device is composed of an amorphous Ga2O3/ZnO heterojunction (GaOx/ZnO) with indium tin oxide (ITO) transparent electrodes, which was prepared using a fully magnetron sputtering method. The fully-transparent device demonstrates exceptional performance at both − 5 V bias and 0 V bias, with a high responsivity of 6.5 × 103 A/W and 13 mA/W, respectively, coupled with excellent stability. Moreover, the device is self-powered due to the built-in electric field formed at the interface of GaOx and ZnO, which efficiently drives carrier motion and generates photocurrent. Finally, we demonstrate the feasibility of transparent devices for solar-blind imaging at 0 V bias by constructing a 5 × 4 GaOx/ZnO heterojunction solar-blind photodetector array, which produces a high-contrast image of the target object. This work provides a new strategy for developing Ga2O3-based fully-transparent self-powered photodetector arrays for solar-blind imaging.

Solar‐Blind Deep‐Ultraviolet Photoconductive Detector Based on Amorphous Ga2O3 Thin Films for Corona Discharge Detection

A low‐cost, high‐efficiency corona discharge detection method is important in ensuring the safety of high‐voltage transmission systems. High‐sensitivity solar‐blind deep‐ultraviolet (SBDU) photodetectors (PD) have obvious advantages in corona discharge detection. Herein, a fully transparent SBDU photoconductive detector with indium tin oxide (ITO) transparent electrodes is successfully constructed based on amorphous Ga2O3 (a‐Ga2O3) thin films. The device demonstrates an ultra‐high responsivity of 1.3 × 104 A W−1, a detectivity of 3.2 × 1014 Jones, and an external quantum efficiency of 6.7 × 106%. In addition, the capability of the ultra‐sensitive fully transparent photoconductive detector is investigated in terms of corona discharge detection. It is established that the device detection distance limit for simulated corona discharge detection is up to 70 cm, that is, the device can effectively detect extremely weak solar‐blind deep‐ultraviolet signals below 204 pW cm−2. A proof‐of‐concept for the future application of easily‐integrated fully transparent amorphous Ga2O3 photoconductive detectors with low manufacturing costs in high‐voltage corona discharge detection is provided.

A Study on Mechanisms Underlying Proton Transport in Proton Pump-type Microbial Rhodopsins

Microbial rhodopsins are photoreceptive membrane proteins composed of seven transmembrane α-helical apoproteins (opsin) and a covalently bound retinal chromophore. Microbial rhodopsins exhibit a cyclic photochemical reaction referred to as photocycle when illuminated. During their photocycles, these proteins perform various functions such as ions transport and photosensing. Among the various functional types of rhodopsins found to date, we have focused on the utility of proton pump-type microbial rhodopsins as optogenetic tools for optical pH control in cells or organelles. To develop effective toolkits for this purpose, a deeper understanding of the proton-pumping mechanism in these rhodopsins may be required. In this review, we first introduce a useful experimental method for measuring rapid transient pH changes with photoinduced proton uptake/release using transparent tin oxide (SnO2) or indium-tin oxide (ITO) electrodes. In addition, we describe the unique pH-dependent behavior of the photoinduced proton transfer sequence as well as the vectoriality of proton transportation in proteorhodopsin (PR) from marine eubacteria. Through intensive ITO experiments over wide pH range, including extremely high or low pH values, in combination with photoelectric measurements using Xenopus oocytes or a thin polymer film "Lumirror," we encountered several interesting observations on photoinduced proton transfer in PR:1) proton uptake/release sequence reversal and potential proton translocation direction reversal under alkali conditions, and 2) fast proton release from D227, a secondary counterion of the protonated retinal Schiff base at acidic pH values.

Smartphone-based portable photoelectrochemical biosensing system for point-of-care detection of urine creatinine and albumin.

Creatinine and albumin are crucial biomarkers for health monitoring and their ratio in urine is an effective approach for albuminuria assessment. Herein, to address the challenges of point-of-care and efficient analysis of the biomarkers simultaneously, we developed a fully integrated handheld smartphone-based photoelectrochemical biosensing system. A miniaturized printed circuit board included a potentiostat for photocurrent measurements and single-wavelength light-emitting diodes (LEDs) for photo-excitation, which was controlled with a Bluetooth-enabled smartphone. Graphitic carbon nitride (g-C3N4)/chitosan nanocomposites were modified on a transparent indium tin oxide (ITO) electrode as photoactive materials. Creatinine was detected through chelate formation with copper ion probes, while albumin was recognized specifically by an antigen-antibody reaction based on immunoassay. The biosensing system demonstrated good linearity and high sensitivity, with detection ranges of 100 μg mL-1 to 1500 μg mL-1 for creatinine, and 9.9 μg mL-1 to 500 μg mL-1 for albumin. Spiked artificial urine samples with different concentrations were tested to confirm the practical validity of the biosensing system, where an acceptable recovery rate ranged from 98.7% to 105.3%. This portable photoelectrochemical biosensing platform provides a convenient and cost-effective method for biofluid analysis, which has an extensive prospect in point-of-care testing (POCT) for mobile health.

Influence of Acid-Doped Poly(ethylene imine) Interlayers on the Performance of Polymer:Nonfullerene Solar Cells.

This work reports that ultrathin polymeric films doped with organic acid molecules can act as an electron-transporting interfacial layer in polymer:nonfullerene solar cells. The polymeric interfacial layers, which consist of poly(ethylene imine) (PEI) doped with 3-hydroxypropane-1-sulfonic acid (HPSA) at various HPSA molar ratios, are introduced between transparent indium-tin oxide (ITO) electrodes and polymer:nonfullerene bulk heterojunction layers. The HPSA-doped PEI (PEI:HPSA) films are optically translucent in the wavelength range of ≈300-800nm, while the acidity of PEI solutions reached ≈pH = 7 at HPSA = 30 mol%. The power conversion efficiency of solar cells is improved by doping 20 mol% HPSA due to the increased short circuit current density without open circuit voltage reduction. The improvement in solar cell performances is attributed to an adequate control of HPSA doping ratios, which spares undoped amine units of PEI for making sufficient net dipole layers with ITO surfaces and makes permanent charges for high electrical conductivity in the layers. The surface morphology and doped states are characterized with atomic force microscopy and X-ray photoelectron spectroscopy.

Wash-free photoelectrochemical DNA detection based on photoredox catalysis combined with electroreduction and light blocking by magnetic microparticles

To obtain a sensitive, wash-free photoelectrochemical biosensor based on electron mediation between an electrode and a photoredox catalyst (PC) label, unavoidable O2-related reactions should have no effect or be beneficial, and the rate of electron mediation should depend on the distance between the PC label and electrode. A wash-free photoelectrochemical biosensor that (i) combines photoredox catalysis of a PC label with electrochemical reduction of an electron mediator, and (ii) uses a light-blocking multilayer of magnetic microparticles was developed. O2 participates as an electron acceptor in photoredox catalysis; thus, increasing rather than decreasing the electrochemical signal. Upon photoirradiation from the opposite side of a transparent indium tin oxide (ITO) electrode in contact with the solution, the light intensity in the solution is sharply decreased by the light-blocking multilayer, which increases the contribution of affinity-bound PC labels on the ITO electrode to the electrochemical signal compared to that of unbound PC labels in solution. Utilizing eosin Y (EY2−) and Fe(CN)64− as the PC and electron mediator (i.e., electron donor), respectively, enabled rapid redox cycling based on photoredox catalysis combined with electroreduction. The cathodic charge is mainly related to electron transfer from Fe(CN)64− to excited EY2− (Type I photosensitization), rather than energy transfer from excited EY2− to O2, which generates 1O2 (Type II photosensitization). The developed detection scheme was applied to wash-free detection of a model target DNA. Detection limits of ∼200 pM were obtained in both phosphate-buffered saline and serum without washing. The developed scheme enables simple photoelectrochemical detection.

Electrochromic polymers based on 3,5-di(9H-carbazol-9-yl)benzonitrile and bithiophene as anodically coloring films for high-contrast and rapid switching electrochromic devices

• A CzBN-containing homopolymer is electrosynthesized. • P(CzBN- co -BTP4) displays three various colors (brown, grayish-blue, and olive green) at different potentials. • P(CzBN- co -BTP) attains high Δ T (59.6 % at 960 nm) and η (174.3 cm 2 /C at 960 nm). • P(CzBN- co -BTP2)/PEDOT ECD presents a high Δ T (43.7 % at 627 nm). A 3,5-di(9H-carbazol-9-yl)benzonitrile (CzBN)-containing homopolymer (P(CzBN)) and five CzBN-containing 2,2′-bithiophene (BTP) copolymers, namely (P(CzBN- co -BTP)), P(CzBN- co -BTP2), P(CzBN- co -BTP3), P(CzBN- co -BTP4), and P(CzBN2- co -BTP), with various feeding molar ratios of CzBN and BTP were electrodeposited on transparent conductive indium tin oxide (ITO) electrodes, and their electrochromic performances were characterized. The P(CzBN- co -BTP4) film exhibited distinct electrochromic behaviors and displayed three different colors (brown, grayish-blue, and olive green) at different potentials. Electrochromic kinetic analyses of the anodic polymers revealed that P(CzBN- co -BTP) had a high transmittance change (Δ T %) (59.6% at 960 nm) and high coloration efficiency (η) (174.3 cm 2 /C at 960 nm) in three-electrode cells. Six dual-layer organic electrochromic devices (ECDs) were constructed using P(CzBN), P(CzBN- co -BTP), P(CzBN- co -BTP2), P(CzBN- co -BTP3), P(CzBN- co -BTP4), or P(CzBN2- co -BTP) as the anodically coloring layers and PEDOT as the cathodically coloring layer. The P(CzBN- co -BTP2)/PEDOT ECD had a high Δ T (43.7% at 627 nm) and a rapid response time (≤2.0 s), while the P(CzBN)/PEDOT ECD had a high η (616.7 cm 2 /C at 625 nm) and adequate optical memories. These electrochromic results suggest that cyano-containing polycarbazoles are promising high-contrast and rapid-response electrodes for ECD applications.

A Hybrid UV-Vis Spectroelectrochemical Approach for Measuring Folic Acid using a Novel Ni-CNF/ITO Electrode

A folic acid (FA) sensor based on UV-Vis spectroelectrochemical technique was developed for the first time using Ni-tipped carbon nanofibers (Ni-CNFs) anchored over an optically transparent indium tin oxide (ITO) electrode. In a novel approach, the biomolecules including FA were oxidized by the Ni-CNF electrocatalyst, and the oxidized folate species were spectrophotometrically detected without requiring any specific recognition element. The electrocatalytic Ni-CNFs, synthesized using chemical vapor deposition technique, increased the electrochemical surface area, thus improving the sensitivity and reducing the charge transfer resistance required for the electro-oxidation of FA. The concentration levels of the oxidized folate species were measured at the characteristic wavelength of 400 nm using the coupled UV-Vis spectroscopy, The sensor performed linearly in the FA range 1 – 100 µg/ml, in the presence of interfering molecules, namely ascorbic acid, uric acid, vitamin – B12, and glucose. The limit of detection was determined as 0.14 µg/ml. The sensor was also successfully tested in commercial multivitamin tablets. In the future study, a sensor based on the hybrid UV-Vis spectroelectrochemical approach can be developed for the measurements of biomolecules such as dopamine, epinephrines, and vitamin B-12, where quantitative measurements using independent spectrophotometric and electrochemical technique are challenging because of convoluted peaks in either cyclic voltammogram or UV-Vis spectra.

P-015 Automated, efficient sorting of sperm using dielectrophoresis (DEP), utilizing the electrical properties of the tail as a biomarker of the viability, even for immotile cells

Abstract Study question Developing a simple and automated method and device that sorts semen cell by cell for eventual application to retrieving rare sperm from severely oligozoospermic samples. Summary answer Over 90% of the viable cells in a sample can be sorted out from non-viable sperm cells and other debris using this method. What is known already The varying electrical properties of different cell types can result in unique frequency dependent dielectrophoretic (DEP) behavior when they are exposed to alternating current (AC). They are either repelled or attracted depending on their properties and the field frequency. This has been applied to sorting rare cells such as circulating tumor cells from blood. We have previously shown that the head and tail of human sperm have different electrical properties. As a result, at certain frequencies of an AC electric field the tails of viable cells (even immotile ones) are attracted to electric field gradients while the heads are distanced. Study design, size, duration Semen samples from several patients at Rambam medical center were collected and cryopreserved. Later the thawed semen samples were then tested in our sorting device. At least one hundred live cells were evaluated in each sample. The percentage of live cells that were successfully sorted out of the original mixture of live sperm cells, dead sperm cells and other debris was assessed. Participants/materials, setting, methods After thawing the samples were stained using CFDA and PI for visual live/dead identification (in actual practice no staining is necessary). The device consists of a polydimethylsiloxane (PDMS) microchannel on a glass slide patterned with Indium Tin Oxide (ITO) transparent electrodes. In the device the sperm are transferred to a low conductivity buffer. A curved electrode then sorts them out of the stream of the cell mixture to an alternate exit. Main results and the role of chance We have successfully demonstrated a new biomarker of live sperm (even immotile ones). The tails of live sperm have a positive (attractive) DEP response while dead sperm react negatively and are repelled from field gradients. At the specific frequencies used the head is simultaneously distanced from the electric fields helping to prevent damage to the DNA during the sorting. We also showed that this effect could be used to sort sperm with over 90% efficiency from a sample with dead sperm and other debris. Since each cell passes the electrodes and is automatically sorted it could possibly be used for severely oligozoospermic and cryptozoospermic samples to find sperm and make more sperm available for more discriminatory sperm selection in such samples. Nowadays such samples are searched manually and the minute number of sperm present is often missed leading to a mistaken azoospermic diagnosis and possibly unnecessary surgery. The components are relatively low cost and the chips disposable allowing for wider implementation. Significant progress was also made in preventing sperm from sticking to the substrates using coatings and a vibrational motor. Additionally, a proof of concept parallelization of the electrodes to increase the throughput was also demonstrated. Limitations, reasons for caution The inherent difficulty with microfluidic technologies is low throughput. Further work is needed to effectively parallelize and optimize the system. Effective pre-processing to clean the sample may also help to increase the throughput. Wider implications of the findings This biomarker can potentially be useful in determining an immotile cell’s viability for ICSI. This technology can also be of potential use for testicular tissue samples where there are many other cell types and debris and it is difficult to find rare sperm. Advanced sperm selection can also be incorporated. Trial registration number not applicable

Solution-Processed Electron-Transport Layer-free Organic Photovoltaics with Liquid Metal Cathodes

Flexible, lightweight, and large-area solar cells provide new power supply opportunities in the renewable energy field and facilitate the supply of power to internet-of-things devices and wearable devices. The choice of printing process technologies is a key parameter for such flexible power sources because of their energy-saving process technology and high throughput rate. In addition to selecting the appropriate printing method for the active and charge transport layers, the development of printed electrodes is critical. Numerous printable materials have been developed to replace conventional evaporated top electrodes. However, achieving fully solution-processed organic photovoltaics (OPVs) with power conversion efficiency (PCE) comparable to OPVs with vacuum-deposited transparent and top electrodes is challenging. This is because of the difficulty of forming a uniform interface between the top solution-processed electrode and the active layers while preventing deterioration. In this study, an electron transport layer-free, eutectic gallium-indium (EGaIn) top-cathode strategy was developed and a record PCE of 12.7% in fully solution-processed, flexible OPVs was achieved. Direct coating of EGaIn on the active layer, in a nitrogen atmosphere, is conducive for energy band matching and obtaining physically perfect interfaces without any penetrations or voids. An average PCE of 14.1% and enhanced operating stability, comparable to conventional OPVs, were achieved with indium tin oxide transparent electrodes by eliminating the electron-transport layer. The fully solution-processed flexible OPVs fabricated with the embedded silver nanowire strategy in ultrathin transparent polyimide, achieved an average PCE of 12.7%, representing a promising technique to meet green and high-throughput energy demands.

Flexible CdSe/ZnS Quantum-Dot Light-Emitting Diodes with Higher Efficiency than Rigid Devices.

Fabrication of high-performance, flexible quantum-dot light-emitting diodes (QLEDs) requires the reliable manufacture of a flexible transparent electrode to replace the conventional brittle indium tin oxide (ITO) transparent electrode, along with flexible substrate planarization. We deposited a transparent oxide/metal/oxide (OMO) electrode on a polymer planarization layer and co-optimized both layers. The visible transmittance of the OMO electrode on a polyethylene terephthalate substrate increased markedly. Good electron supply and injection into an electron-transporting layer were achieved using WOX/Ag/ WOX and MoOx/Ag/MoOX OMO electrodes. High-performance flexible QLEDs were fabricated from these electrodes; a QLED with a MoOX/Ag/ MoOX cathode and an SU-8 planarization layer had a current efficiency of 30.3 cd/A and luminance more than 7 × 104 cd/m2. The current efficiency was significantly higher than that of a rigid QLED with an ITO cathode and was higher than current efficiency values obtained from previously reported QLEDs that utilized the same quantum-dot and electron-transporting layer materials as our study.

A highly transparent haptic device with an extremely low driving voltage based on piezoelectric PZT films on glass

When a substrate is excited to exhibit more than 1 µm out-of-plane displacement at an ultrasonic frequency, a silent change of friction force could be clearly felt by human fingers when touch it. This is called the surface haptic feedback based on friction modulation. In this study, we designed and fabricated a highly transparent haptic device based on piezoelectric Pb(Zr,Ti)O3 (PZT) films on glass. Standing lamb waves in the vibrating plate resulting in a haptic effect was generated under sinusoidal excitation at 22.5 kHz. An extremely low unipolar voltage of 10 VPeak-to-Peak achieved a displacement of 1 µm. The displacement reached as high as 4 µm when the voltage increased to 24 VPeak-to-Peak. The average transmittance of the whole films including the PZT and the electrodes on the glass reached about 75%. The key outcome of this technology is the design of vibration modes and the effective integration of 2-µm-thick PZT film with transparent indium tin oxide (ITO) electrodes on glass.