Dopant-Tunable Ultrathin Transparent Conductive Oxides for Efficient Energy Conversion Devices

Coaxial Electrohydrodynamic Printing of Microscale Core-Shell Conductive Features for Integrated Fabrication of Flexible Transparent Electronics

Reliable insulation of microscale conductive features is required to fabricate functional multilayer circuits or flexible electronics for providing specific physical/chemical/electrical protection. However, the existing strategies commonly rely on manual assembling processes or multiple microfabrication processes, which is time-consuming and a great challenge for the fabrication of flexible transparent electronics with microscale features and ultrathin thickness. Here, we present a novel coaxial electrohydrodynamic (CEHD) printing strategy for the one-step fabrication of microscale flexible electronics with conductive materials at the core and insulating material at the outer layer. A finite element analysis (FEA) method is established to simulate the CEHD printing process. The extrusion sequence of the conductive and insulating materials during the CEHD printing process shows little effect on the morphology of the core-shell filaments, which can be achieved on different flexible substrates with a minimum conductive line width of 32 ± 3.2 μm, a total thickness of 53.6 ± 4.8 μm, and a conductivity of 0.23 × 107 S/m. The thin insulating layer can provide the inner conductive filament enough protection in 3D, which endows the resultant microscale core-shell electronics with good electrical stability when working in different chemical solvent solutions or under large deformation conditions. Moreover, the presented CEHD printing strategy offers a unique capability to sequentially fabricate an insulating layer, core-shell conductive pattern, and exposed electrodes by simply controlling the material extrusion sequence. The resultant large-area transparent electronics with two-layer core-shell patterns exhibit a high transmittance of 98% and excellent electrothermal performance. The CEHD-printed flexible microelectrode array is successfully used to record the electrical signals of beating mouse hearts. It can also be used to fabricate large-area flexible capacitive sensors to accurately measure the periodical pressure force. We envision that the present CEHD printing strategy can provide a promising tool to fabricate complex three-dimensional electronics with microscale resolution, high flexibility, and multiple functionalities.

Synthesis, Properties, and Application of Ultrathin and Flexible Tellurium Nanorope Films: Beyond Conventional 2D Materials

Nanomaterials that can be easily processed into thin films are highly desirable for their wide range of applicability in electrical and optical devices. Currently, Te-based 2D materials are of interest because of their superior electrical properties compared to transition metal dichalcogenide materials. However, the large-scale manufacturing of these materials is challenging, impeding their commercialization. This paper reports on ultrathin, large-scale, and highly flexible Te and Te-metal nanorope films grown via low-power radiofrequency sputtering for a short period at 25 °C. Additionally, the feasibility of such films as transistor channels and flexible transparent conductive electrodes is discussed. A 20 nm thick Te-Ni-nanorope-channel-based transistor exhibits a high mobility (≈450 cm2 V-1 s-1 ) and on/off ratio (105 ), while 7 nm thick Te-W nanorope electrodes exhibit an extremely low haze (1.7%) and sheet resistance (30 Ω sq-1 ), and high transmittance (86.4%), work function (≈4.9 eV), and flexibility. Blue organic light-emitting diodes with 7 nm Te-W anodes exhibit significantly higher external quantum efficiencies (15.7%), lower turn-on voltages (3.2 V), and higher and more uniform viewing angles than indium-tin-oxide-based devices. The excellent mechanical flexibility and easy coating capability offered by Te nanoropes demonstrate their superiority over conventional nanomaterials and provide an effective outlet for multifunctional devices.

Review of Electrochemically Synthesized Resistive Switching Devices: Memory Storage, Neuromorphic Computing, and Sensing Applications

Resistive-switching-based memory devices meet most of the requirements for use in next-generation information and communication technology applications, including standalone memory devices, neuromorphic hardware, and embedded sensing devices with on-chip storage, due to their low cost, excellent memory retention, compatibility with 3D integration, in-memory computing capabilities, and ease of fabrication. Electrochemical synthesis is the most widespread technique for the fabrication of state-of-the-art memory devices. The present review article summarizes the electrochemical approaches that have been proposed for the fabrication of switching, memristor, and memristive devices for memory storage, neuromorphic computing, and sensing applications, highlighting their various advantages and performance metrics. We also present the challenges and future research directions for this field in the concluding section.

Rapid photonic curing effects of xenon flash lamp on ITO-Ag-ITO multilayer electrodes for high throughput transparent electronics

High-throughput transparent and flexible electronics are essential technologies for next-generation displays, semiconductors, and wearable bio-medical applications. However, to manufacture a high-quality transparent and flexible electrode, conventional annealing processes generally require 5 min or more at a high temperature condition of 300 °C or higher. This high thermal budget condition is not only difficult to apply to general polymer-based flexible substrates, but also results in low-throughput. Here, we report a high-quality transparent electrode produced with an extremely low thermal budget using Xe-flash lamp rapid photonic curing. Photonic curing is an extremely short time (~ μs) process, making it possible to induce an annealing effect of over 800 °C. The photonic curing effect was optimized by selecting the appropriate power density, the irradiation energy of the Xe-flash lamp, and Ag layer thickness. Rapid photonic curing produced an ITO-Ag-ITO electrode with a low sheet resistance of 6.5 ohm/sq, with a high luminous transmittance of 92.34%. The low thermal budget characteristics of the rapid photonic curing technology make it suitable for high-quality transparent electronics and high-throughput processes such as roll-to-roll.

All-atmospheric fabrication of Ag-Cu core-shell nanowire transparent electrodes with Haacke figure of merit >600 × 10-3 Ω-1

Transparent conducting electrodes (TCEs) are essential components in devices such as touch screens, smart windows, and photovoltaics. Metal nanowire networks are promising next-generation TCEs, but best-performing examples rely on expensive metal catalysts (palladium or platinum), vacuum processing, or transfer processes that cannot be scaled. This work demonstrates a metal nanowire TCE fabrication process that focuses on high performance and simple fabrication. Here we combined direct and plating metallization processes on electrospun nanowires. We first directly metallize silver nanowires using reactive silver ink. The silver catalyzes subsequent copper plating to produce Ag-Cu core-shell nanowires and eliminates nanowire junction resistances. The process allows for tunable transmission and sheet resistance properties by adjusting electrospinning and plating time. We demonstrate state-of-the-art, low-haze TCEs using an all-atmospheric process with sheet resistances of 0.33 Ω sq^-1 and visible light transmittances of 86% (including the substrate), leading to a Haacke figure of merit of 652 × 10^-3 Ω^-1. The core-shell nanowire electrode also demonstrates high chemical and bending durability.

A crack templated copper network film as a transparent conductive film and its application in organic light-emitting diode

In this paper, a highly transparent, low sheet resistance copper network film fabricated by a crack template, which made by drying an acrylic based colloidal dispersion. The fabricated copper network film shows excellent optoelectronic performances with low sheet resistance of 13.4 Ω/sq and high optical transmittance of 93% [excluding Polyethylene terephthalate (PET) substrate] at 550 nm. What’s more, the surface root mean square of the copper network film is about 4 nm, and the figure of merit is about 380. It’s comparable to that of conventional indium tin oxide thin film. The repeated bending cycle test and adhesive test results confirm the reliability of the copper network film. As a transparent conductive film, the copper network film was used as an anode to prepare organic light-emitting diode (OLED). The experiment results show that the threshold voltage of the OLED is less than 5 V and the maximum luminance is 1587 cd/m2.