Transparent Electrode Applications Research Articles

Laser shock-enabled optical–thermal–mechanical coupled welding method for silver nanowires

Silver nanowires (AgNWs) are recognized as highly promising materials for flexible and transparent electrode applications. However, existing material-processing methods fail to achieve uniform and reliable AgNWs junctions. In this study, we propose a new method using the laser shock effect combined with the laser heating effect, for creating AgNW junctions within thin films. We explored the welding mechanism of AgNWs through optic-thermal welding, laser shock-enabled mechanical welding, and laser-shock-enabled optical-thermal-mechanical (LS-OTM) experiments, as well as numerical simulations, and the results demonstrate that the innovative mechanism of the LS-OTM process lies in its utilization of laser shock to adjust the gap between the nanowire junctions, which in turn achieves a fine control of the thermal effect of the heating laser localised surface plasmon resonance, and the atomic diffusion in the solid state at intermediate temperature under the action of the impact force is the mechanism of the formation of high-quality junctions. We prepared flexible transparent conductive films and studied their transmittance, conductivity, and thermal properties, the results show that the flexible transparent conductive films prepared by LS-OTM welding method have excellent transmittance, conductivity, and thermal properties, this verifies the feasibility and effectiveness of this processing strategy. The LS-OTM method is a viable solution for manufacturing transparent, conductive films from AgNWs for emerging applications such as flexible heated films, flexible displays, and wearable medical devices.

Silver Nanowires (AgNWs) Post-Treatment Effect in Application of Flexible Transparent and Conductive Electrodes: A Mini Review

Transparent flexible electrodes (TFEs) are extremely crucial for expanding flexible and wearable electronic devices. Silver nanowires (AgNWs) have been extensively investigated as an alternative to replace Indium Tin Oxide (ITO) as a commercial TFE due to their high conductivity, transparency, and flexibility. AgNWs have replaced ITO-based electrodes as the preferred approach in flexible, transparent, and conductive electrodes (FTCE). AgNWs outperform other materials, such as Reduced Graphene Oxide (RGO), ceramic material, Carbon Nanotubes (CNT), and conductive polymers, in terms of electrical conductivity, transmittance, flexibility, and low sheet resistance. Numerous techniques, including as electrospinning, spray coating, spin coating, and doctor blades, are used to use AgNWs as flexible substrates. Seed-based growth and template-assisted synthesis are two fundamental synthesis techniques that could be used to generate AgNWs. However, poor adhesiveness, and thermal and electrical stability, begin to be bottlenecks for AgNWs as high deployment in a variety of devices. So AgNWs synthesis process began to shift to other methods, such as wet chemical and polyol. In this paper, short and clear summary of various advances including post-treatment methods such as UV radiation, microwave, sonication, quenching, and so on is conducted to be one step forward to test mechanical properties and to improve AgNWs performance.

Flexible Embedded Metal Meshes by Sputter-Free Crack Lithography for Transparent Electrodes and Electromagnetic Interference Shielding.

A facile and novel fabrication method is demonstrated for creating flexible poly(ethylene terephthalate) (PET)-embedded silver meshes using crack lithography, reactive ion etching (RIE), and reactive silver ink. The crack width and spacing in a waterborne acrylic emulsion polymer are controlled by the thickness of the polymer and the applied stress due to heating and evaporation. Our innovative fabrication technique eliminates the need for sputtering and ensures stronger adhesion of the metal meshes to the PET substrate. Crack trench depths over 5 μm and line widths under 5 μm have been achieved. As a transparent electrode, our flexible embedded Ag meshes exhibit a visible transmission of 91.3% and sheet resistance of 0.54 Ω/sq as well as 93.7% and 1.4 Ω/sq. This performance corresponds to figures of merit (σDC/σOP) of 7500 and 4070, respectively. For transparent electromagnetic interference (EMI) shielding, the metal meshes achieve a shielding efficiency (SE) of 42 dB with 91.3% visible transmission and an EMI SE of 37.4 dB with 93.7% visible transmission. We demonstrate the highest transparent electrode performance of crack lithography approaches in the literature and the highest flexible transparent EMI shielding performance of all fabrication approaches in the literature. These metal meshes may have applications in transparent electrodes, EMI shielding, solar cells, and organic light-emitting diodes.

Tailoring Optoelectronic Properties of ZnO Films Through Synergistic Mg and B Co-Doping for Unprecedented High-Performance Transparent Electrode Applications

The quest for indium-free transparent conductive electrodes with enhanced optical band gaps and superior electrical conductivity is imperative for the advancement of flexible electrochromic devices. This study presents a groundbreaking approach wherein composite ZnO films, incorporating Mg and/or B dopants through a facile sol–gel spin coating method, are meticulously crafted and systematically scrutinized for their optoelectrical properties. Our findings reveal that Mg doping primarily influences the optical band gap, while B doping facilitates the augmentation of free electrons by modulating morphology and electronic defect states. Optimal performance is achieved with pure Mg doping at an atomic molar concentration of 0.2, resulting in a ZnMgO film boasting an exceptional average transmittance of 98.79% and an impressively low electrical resistivity of 15.3 Ω·cm. Although pure B doping compromises the crystalline quality, it significantly reduces electrical resistivity. Intriguingly, co-doping with Mg at an atomic molar concentration of 0.2 introduces challenges to crystalline quality but enriches the composite film with additional charge carriers, leading to a reduction in bandgap and a remarkable drop in resistance to 6.2 Ω·cm. This innovative work not only sheds light on the delicate balance between Mg and B doping in ZnO films but also paves the way for unparalleled opportunities in the development of high-performance transparent conductive electrodes for flexible electrochromic devices.

Irradiation methods for engineering of graphene related two-dimensional materials

The research community has witnessed an exceptional increase in exploring graphene related two-dimensional materials (GR2Ms) in many innovative applications and emerging technologies. However, simple, low-cost, sustainable, and eco-friendly methods to manufacture large quantities and high-quality GR2Ms still remain an unsolved challenge. To address limitations of conventional wet chemical-based exfoliation methods using graphite resources, the top-down irradiation approach has proven to be an ultrafast, effective, and environmentally friendly technology for scalable exfoliation, production, and processing of GR2Ms providing new properties for emerging applications. Significant advancements have been made for preparation of broad range of GR2Ms from graphite, such as graphene, graphene oxide, and reduced graphene oxide, and their doped, functionalized and modified forms over the past two decades, thanks to the availability of photon and ion irradiation techniques, such as microwave, infrared, ultraviolet, solar, x-ray, gamma, laser, and plasma. This review presents recent advances on the application of these various irradiation techniques and highlights their mechanism, differences in properties of prepared GR2Ms, and their advantages and disadvantages in comparison with other conventional methods. The review provides an insight into the irradiation strategies and their prospective applications to produce, at a large scale, low-cost, high-quality GR2Ms for practical applications in transparent electrodes, optoelectronic devices, sensors, supercapacitors, protective coatings, conductive inks, and composites.

SnO2-Coated Silver Nanowire Networks as a Physical Model Describing Their Reversible Domain under Electrical Stress for Stable Transparent Electrode Applications

SnO₂-Coated Silver Nanowire Networks as a Physical Model Describing Their Reversible Domain under Electrical Stress for Stable Transparent Electrode Applications

Tetrabutylammonium Tribromide-Induced Synthesis of Silver Nanowires with Ultrahigh Aspect Ratio for a Flexible Transparent Film.

Silver nanowires (AgNWs) have gained significant attention from researchers as a promising material for producing flexible transparent conductive films, which can be utilized in touch and display screens. Thereinto, the ultrahigh aspect ratio AgNW network can theoretically decrease the contact resistance effectively while still retaining considerable mechanical and optical properties. However, fabrication of high-quality AgNWs with a fine diameter and high aspect ratio is still challenging. Herein, a simple and robust approach to synthesize ultrahigh aspect ratio AgNWs is presented. This study successfully fabricated AgNWs with the highest aspect ratio up to ∼4000 and an average length of ∼72 μm by utilizing tetrabutylammonium tribromide as an auxiliary additive. The manifestation of tetrabutylammonium tribromide was proven to be beneficial for the generation of silver seeds and the expansion of AgNWs. The obtained AgNWs were utilized to create a transparent conductive film that showed low sheet resistance of 22.4 Ω/sq and high transmittance and low haze of 87.71 and 4.15%, respectively. The transmittance and haze of the vacant poly(ethylene terephthalate) support were 90.13 and 2.05%, thereby offering great potential for application in flexible transparent electrodes.

Air and Vacuum Annealing Effect on the Highly Conducting and Transparent Properties of the Undoped Zinc Oxide Thin Films Prepared by DC Magnetron Sputtering

In this study, we aim to investigate the effect of zinc interstitials (Zni) and oxygen vacancies (VO) on the ZnO electrical conductivity. ZnO films were synthesized via DC magnetron sputtering process using pure Zn target in gases mixture of Ar/O2 = 80/17.5 (sccm). In order to improve the optical and electrical prosperities, the obtained films were subjected to air and vacuum annealing treatment. Several techniques such as field emission scanning electron microscopy (FESEM), Grazing Incidence X-ray Diffraction (GIXRD), Raman spectroscopy, photoluminescence spectroscopy (PL) and UV-visible were used to study the influence of heat treatment on structural and physical properties of ZnO films. Electrical conductivity of ZnO thin films was determined by measuring the sheet resistance and thickness of the films. XRD results confirm the synthesis of annealed ZnO films of the hexagonal structure with a preferential orientation along the (002) plane. The average crystallite size is altered between 22.6 to 28.4 nm dependent on the plan orientation of the ZnO film. Morphology and crystallinity of the ZnO structure could efficiently control the transmittance, electrical resistivity and optical band gap. As deposited ZnO film showed a lower electrical resistivity of 2.72×10-3 Ωcm due to the Zn-rich conditions. Under vacuum annealing, a combination of low resistivity (1.17×10-2 Ωcm) and better optical transmittance (87 %) are obtained. ZnO films developed in this study with high transmittance and low resistivity and good electro-optical quality supports their use in transparent and conductive electrode applications. The plan presentation was visualized using Vesta, with the lattice parameter set as follows: a = b = 3.249 Å; c = 5.207 Å; α = β = 90°; γ = 120°. Based on the construction and optimization of primitive cells, the supercells were constructed and then optimized. Finally, (002) and (103) planes were cut and the planar supercell structure was constructed. In order to make a plane representation for the solid bulk with 10 Å of thickness.

Facile preparation of conductive carbon-based membranes on dielectric substrates.

Graphene has attracted much research attention due to its outstanding chemical and physical properties, such as its excellent electronic conductivity, making it as a useful carbon material for a variety of application fields of photoelectric functional devices. Herein, a new method for synthesizing conductive carbon membranes on dielectric substrates via a low-temperature thermodynamic driven process is developed. Although the obtained films exhibit low crystallinity, their electrical, wetting, and optical properties are acceptable in practice, which opens up a new avenue for the growth of carbon membranes and may facilitate the applications of transparent electrodes as potential plasma-free surface-enhanced Raman scattering (SERS) substrates.

Simple Route to Increase Electrical Conductivity and Optical Transmittance in Graphene/Silver Nanoparticles Hybrid Suspensions

Electrical and optical properties of graphene/silver nanoparticles hybrid suspensions intended for use in inkjet printing technologies were studied. Few-layered graphene particles were manufactured via a direct ultrasonic-assisted liquid-phase exfoliation route in water/surfactant system, whereas silver nanoparticles were synthetized using a polyol process. Hybrid suspensions for graphene/silver nanoparticles mixtures showed significant reduction in mean particle size while electrical conductivity remained almost intact even after thorough centrifugation. Structuring effects in mixed colloids were very pronounced as both electrical conductivity and optical transmission showed maxima at 65 wt.% graphene. Suspensions with conductivities above 300 μSm/cm, much higher than previously reported, were obtained, and resulted in the manufacturing of films with less than 10% optical absorption throughout the visible region. These samples did not demonstrate absorption peaks attributed to silver nanoparticles’ surface plasmon resonance, which is suitable for transparent electrode applications. Suspension properties at optimal composition (65 wt.% graphene) are very promising for printed electronics as well as transparent conductive coating applications. In the paper, we establish that the optimal suspension composition matches that of the film; therefore, more attention should be paid to carefully studying electrically conductive suspensions.

Shape Dependence of Silver Nanowires on Synthesis Conditions and it’s Effect on the Optical and Electrical Properties

As the market share of optoelectronic devices grows yearly, the transparent conductive electrodes that guarantee device performance subsequently gain attention. In order to solve the cost issue of the most commonly commercialised transparent conductive electrodes (indium tin oxide) and the problem that they cannot be used in portable wearable devices, flexible carbon-based hybrid nanomaterials are considered as an alternative. But, it still suffers the complicated synthesis process. Thus, silver nanowire (AgNW) is regarded as the most promising material with advantages of the facile synthesis process, high conductivity and transparency. The synthesis conditions and AgNW morphology are believed to be vital for their optical and electrical properties. This research investigated the effect of synthesis conditions (capping agent molecular weight and compositions, reaction temperature and the stirring rate) and discussed the connection between the optical transmission and electrical resistance of coated films fabricated by AgNW with various morphology. Results show that heavier capping agents with more viscous solutions are more favourable for long wire growth, and mixed capping agent solutions can achieve higher aspect ratios. Both relatively low reaction temperature and no stirring could prevent silver particles nucleation and agglomeration, achieving longer nanowires. The AgNW-coated film by nanowires with longer lengths could have more advantages in the trade-off between conductivity and transparency for better performance. This article illustrates and explains the influence of factors in the synthesis process on its morphology and functionality, creating more possibilities for the development and application of flexible transparent conductive electrodes.

Low-temperature fabrication of high-performance AlN/Ag/AlN thin films for transparent electrode applications

Low-temperature fabrication of high-performance AlN/Ag/AlN thin films for transparent electrode applications

Single-step treatment to improve conductivity of PEDOT:PSS by hydrobromic acid solution for application of transparent electrode

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS) is the most well-known organic conducting material due to tunable conductivity, high transparency, facile processability and stability. Single-step post-treatment by DMSO solvent and hydrobromic acid solution in DMSO improved the electrical conductivity of pristine PEDOT:PSS from 0.4 S/cm to 632 S/cm and 1813 S/cm, respectively. Mechanism of conductivity improvement is associated to diffusion of DMSO solvent and HBr-DMSO solution into PEDOT:PSS which induce charge screening by forming hydrogen bonding and weaken the electrostatic interactions of conducting PEDOT and insulating PSS. This affect the phase separation of PEDOT and PSS, and washing away the separated excess-PSS result in conductive PEDOT grains observed by increased surface roughness through AFM height images. Analysis of Raman and vis-NIR spectra and Hall-effect measurement confirmed the improvement in oxidation state of PEDOT:PSS by HBr-DMSO treatment. Treated films showed very low sheet resistance of 85 Ω/□ with high transparency of 90% leading to figure of Merit (FOM) of 38 for transparent electrode. Treated film as anode of organic solar cell have shown better photovoltaic performance with PCE of 2.64% compared to PCE of 0.055% by untreated PEDOT:PSS. These results suggest that the treated PEDOT:PSS can replace ITO electrode in organic optoelectronic applications. • Single step post-treatment of PEDOT:PSS by DMSO and HBr-DMSO improved the conductivity. • Mechanism is attributed to phase separation, loss of PSS, higher conducting PEDOT by DMSO and further oxidation by HBr. • Mechanism is verified by AFM, UV–vis–NIR, Raman spectroscopy and Hall-effect measurement. • Improved conductivity with high transparency by HBr-DMSO resulted high figure of merit of 38 for transparent electrode. • Treated-film as anode of solar cell successfully improved the PCE and can be used for organic optoelectronic applications.

ITO films with different preferred orientations prepared by DC magnetron sputtering

The preparation process of ITO film has been fully matured, but the precise control of preferred orientation has always been a difficult problem. ITO films with different preferred orientations were prepared on glass substrates by DC sputtering with a ceramic target, and the precise control of ITO films with (211), (222), (400), and (440) high preferred orientations was achieved. The effect of technological conditions on the preferred orientation of ITO film was systematically studied, and the growth mechanism of the preferred orientation of ITO film was analyzed by surface energy calculation. (400) preferred film has excellent electric properties (ρ = 2.633 × 10−4 Ω cm) and an average transmittance of visible light (87.1%). Compared with the other three preferred oriented films, (400) preferred film has the highest quality factor and surface energy, which is attributed to the abundance of the surface dangling-bonds of Indium atoms on the end surface of (400) preferred film, which provides higher carrier transfer capacity for ITO film. (400) Preferentially oriented films are of great significance for the application of transparent electrodes.

유기박막 태양전지용 ITO 투명전극 최적화 연구

This study analyzes the optical characteristics of the ITO thin film deposited using DC magnetron sputtering to study the characteristics of ITO transparent electrodes for organic solar cells deposited by sputtering. For the experiments, the pressure ranged from 1–3 mTorr, and the applied voltage ranged from 260–340 V at 10 V intervals.
 The results of light transmittance, refractive index, and surface images were analyzed using equipment such as a spectrophotometer, an elliptical polarization analyzer, and a scanning microscope. As a result, under a pressure of at least 1 mTorr, light transmittance of at least 90% was measured, and the refractive index of the thin film had an excellent value of at least 2. Therefore, optimal conditions were established for the application of ITO transparent electrodes for organic solar cells.

Optical Study of Few‐Layer Graphene Treated by Oxygen Plasma

Oxygen plasma treatment is often used to clean the surface or etch graphene for functional structures. Some unique properties such as photoluminescence (PL), energy bandgap engineering, and so on are presented in single‐layer graphene (SLG). Compared with SLG, few‐layer graphene (FLG) has higher luminescence intensity, slower decay rate, and better controllability. It is more universal in the application of new optoelectronic devices and transparent electrodes. So, a systematic study is provided to analyze the mechanism between chemical vapor deposition of few‐layer graphene and oxygen plasma process based on the optical characterization method. Surface morphology, structural defects, resistance change, chemical state, and PL are traced and investigated under different oxygen plasma treatment times. The CO and CO bonds on the surface of the FLG appear to increase and then decrease with oxygen plasma etching based on X‐ray photoelectron spectroscopy (XPS) characterization. A linear square resistance change is presented from 1.4 to 4.8 kΩ sq−1. Besides that, an obvious redshift–blueshift change is produced in fluorescence characteristic spectra. Herein, comprehensive research on the influencing mechanism of graphene and oxygen treatment is exhibited, which provides the potential to construct optoelectronic devices.

Centrifugal Spinning Enables the Formation of Silver Microfibers with Nanostructures.

Silver nanowires (AgNWs) have received much attention and application in transparent electrodes, wearable electronic devices, and sensors. The hope is for these nanowires to eventually replace the most commonly used transparent electrode material—indium tin oxide (ITO). However, electrospinning used for the preparation of AgNWs on a large scale is limited by its low productivity and high electric field, while the alcohol-thermal method is limited to mixing by-product silver nanoparticles in silver nanowires. We demonstrate a novel and simple centrifugal spinning approach in order to successfully fabricate ultra-long silver microfibers based on AgNO3 and polyvinyl pyrrolidone (PVP). The centrifugal-spun precursor fiber and silver fiber can be prepared to as thin as 390 and 310 nm, respectively. Annealed fibers show typical nanostructures with grains down to a minimum size of 51 nm. Combinations of different parameters, including concentrations of PVP, needle size, and annealing temperature are also investigated, in order to optimize the spinning process of ultra-long silver microfibers. The feasibility of preparing silver microfibers by centrifugal spinning is preliminarily verified, examining prospects for mass production. Furthermore, numerous strategies related to assisting the creation of silver nanofibers using centrifugal spinning are presented as possibilities in future development.

Silver nanowire synthesis analyzing NaCl, CuCl2, and NaBr as halide salt with additional thermal, acid, and solvent post-treatments for transparent and flexible electrode applications

Silver nanowire synthesis analyzing NaCl, CuCl2, and NaBr as halide salt with additional thermal, acid, and solvent post-treatments for transparent and flexible electrode applications

Photo responsive transport properties of hydrothermally synthesized SnO2 layered nanoflakes/Au Schottky junction

Stannic oxide (SnO2) nano-materials has been drawing attentions for applications in transparent electrodes, hazardous-gas sensors, electron transport layers in thin-film solar cells, microelectronics, etc. In this present report, we have analyzed the junction characteristics of the hydrothermally synthesized SnO2 layered nano-flakes (LNFs). The two-dimensional flake like structure of the SnO2 samples was verified from the scanning electron microscopy (SEM) micrographs with a mean thickness of 11.70 nm. The chemical composition of the LNFs was found to be 1:3.51 (Sn:O), from the energy dispersive x-ray spectroscopy (EDS) study. The UV–Vis absorption analysis validates the quantum confinement effect from the widening (blue shifting) of the bandgap to 3.75 eV. The junction characteristics of the indium tin oxide (ITO)/ SnO2 LNFs/gold (Au) device depict the Schottky type properties with barrier potentials, 0.85 eV and 0.63 eV in dark and illumination conditions respectively. However, in both conditions, the ideality factor remains unaltered (0.93). The light induced diminution of the barrier potential and confinement induced widening of band gap make the LNFs suitable for photo-sensors and solar cells.

Wafer‐Scale Graphene Anodes Replace Indium Tin Oxide in Organic Light‐Emitting Diodes

AbstractIndium tin oxide (ITO) is widely used for transparent electrode applications due to its high electrical conductivity and relatively straightforward deposition technology. However, there are long standing concerns for its use due to the limited availability of indium in the Earth's crust. Graphene is considered as a promising material for replacing ITO but for this to become possible, a low‐cost and scalable fabrication method that produces graphene with comparable performance to ITO is required. By taking advantage of high‐quality monolayer graphene directly deposited on a transparent substrate using a commercially available metal–organic chemical vapor deposition (MOCVD) system, graphene‐based organic light‐emitting diodes (OLEDs) without the use of metal catalysts or a graphene transfer process are developed. The as‐grown graphene is patterned using photolithography and its conductivity is enhanced by doping with nitric acid prior to deposition of the OLED stack. The electrical and optical performances of the as‐fabricated graphene‐based OLEDs are identical to the control devices with conventional ITO anodes. All the processes used in the fabrication of graphene‐based OLEDs can be performed at wafer scale. This paper demonstrates the potential for graphene to replace ITO as anodes in OLED devices in a technologically and commercially effective manner.