Electrodes For Flexible Devices Research Articles

In situ growth of a redox-active metal-organic framework on electrospun carbon nanofibers as a free-standing electrode for flexible energy storage devices.

The rational construction of free-standing and flexible electrodes for application in electrochemical energy storage devices and next-generation supercapacitors is an emerging research focus. Herein, we prepared a redox-active ferrocene dicarboxylic acid (Fc)-based nickel metal-organic framework (MOF) on electrospun carbon nanofibers (NiFc-MOF@CNFs) via an in situ approach. This in situ approach avoided the aggregation of the MOF. The NiFc-MOF@CNF flexible electrode showed a high redox-active behavior owing to the presence of ferrocene and flexible carbon nanofibers, which led to unique properties, including high flexibility and lightweight. Furthermore, the prepared electrode was utilized in a supercapacitors (SC) without the use of any binder, which achieved a specific capacity of 460 C g-1 at 1 A g-1 with an excellent cyclic retention of 82.2% after 25 000 cycles and a good rate capability. A flexible asymmetric supercapacitor device was assembled, which delivered a high energy density of 56.25 W h kg-1 and a long-lasting cycling performance. Also, the prepared electrode could be used as a freestanding electrode in flexible devices at different bending angles. The obtained cyclic voltammetry curves showed negligible changes, indicating the high stability and good flexibility of the electrode. Thus, the use of the in situ strategy can lead to the uniform growth of redox-active MOFs or other porous materials on CNFs.

Exploring the possibility of using MWCNTs sheets as an electrode for flexible room temperature NO2 detection

In the last few years, significant progress has been made in nanotechnology, especially in the fabrication of sensors. Generally, metal electrodes are used in devices. Here, carbon nanotubes sheet has been used as an electrode and tin oxide nanoparticles made by the sol-gel method as the sensing material. The combination was used for sensing NO2 in the atmosphere at room temperature. For the MWCNT ​+ ​SnO2 (modified MWCNT) case, there was no immediate recovery for 14 ​ppm gas, and for 28 ppm and 56 ​ppm, recovery times were 13 ​s and 6 ​s, respectively. Using modified MWCNTs sheets as an electrode for flexible devices is the novelty of this work.

Realizing high-voltage and ultralong-life supercapacitors by a universal interfacial engineering strategy

Low energy density hinders the development of supercapacitors in the market of large hybrid power equipment and electric vehicles that demand much higher energy density. Herein, we conduct a facile and environmentally friendly method to modify the electrodes of supercapacitors through coating a dielectric thin film by atomic layer deposition (ALD) technique, which profoundly improves the electrochemical performance of the electrodes. In specific, the gravimetric capacitance of the ALD-Ti modified electrodes is characterized by 35% significant promotion comparing to the commercialized pristine counterparts, and the operational voltage window of the ALD treated electrodes can expand to 3.5 V using organic electrolyte with remarkable capacitance retention (over 83%) even after 20000 cycles. Besides, appropriate models are established to discuss the detailed charge storage mechanism and possible reasons for good stability of modified electrodes under higher operational voltage. Moreover, the excellent rate and cycling performance of ALD modified electrodes in flexible electrochemical double-layer capacitor (EDLCs) at the bending state substantiates the application superiority of ALD modified electrodes in flexible devices. The unusual combination of charge storage mechanisms of dielectric capacitors and EDLCs established in our work represents specific properties in great need for energy storage applications.

Application of patterned Ag-nanowire networks to transparent thin-film heaters and electrodes for organic light-emitting diodes

We present patterned Ag-nanowire (AgNW) networks for their application to transparent electrodes in flexible devices. Using capillary-force-based soft lithography (CFL), we formed 25- to 30-µm-wide line patterns of AgNWs on flexible polymer substrates. Organic light-emitting diodes (OLEDs) and transparent thin-film heaters (TFHs) were successfully fabricated on the patterned substrates, which verified the potential of AgNW patterns formed by CFL as interconnects in flexible devices.

Carbon-Doped Hexagonal Boron Nitride: Analysis as π-Conjugate Molecules Embedded in Two Dimensional Insulator

We analyzed the electronic structures of carbon-doped hexagonal boron nitride, focusing on the comparison with the corresponding π-conjugate hydrocarbon molecules and odd-number substitution by first principle calculation. The band gaps are about the half that of the HOMO-LUMO gaps of corresponding hydrocarbons, except for the cis-butadiene structure in which aromatic hexagonal ring formation is important. Odd number doping makes metallic materials with very different work functions, depending upon the difference in B and N numbers, and has an expected application as electrodes for flexible devices.

A versatile ultra-thin Au nanomesh from a reusable anodic aluminium oxide (AAO) membrane

We demonstrated multiple replications of versatile ultra-thin Au nanomeshes from a single porous anodic aluminium oxide (AAO) membrane as a reusable replication master. A bilayered film of Ag and Au was sequentially deposited on nanoporous AAO (i.e., Au/Ag/AAO), in which the Ag layer sandwiched in-between the Au layer and AAO serves as a sacrificial layer for separating the Au film from the oxide membrane during selective wet-chemical etching of Ag in HNO3 solution. The structure of the separated Au film is characterized by a free-standing nanomesh, the hole array pattern and pitch distance of which are defined by the AAO replication master. Ultra-thin Au meshes can be transferred onto substrates of choice without any structural failure. On the other hand, our repeated replication experiments have revealed that a single porous AAO replication master can be reused more than 30 times without significant structural changes. In the present work, we demonstrated the versatility of replicated Au nanomeshes in various nanofabrications, including preparation of extended arrays of Si nanowires (SiNWs) by metal-assisted chemical etching of silicon wafers and surface patterning of polymeric substrates with sub-100 nm resolution. The applicability of Au meshes as an electrode for flexible devices was manifested by comparable resistance values of Au meshes on the polymer substrate, viz., polyethylene terephthalate (PET), to a continuous Au film and stable I–V behaviours regardless of its bending state. The present approach of multiple replications of metal meshes from a single AAO membrane can be readily extended to other metallic materials and is time- and cost-effective compared to conventional lithographic methods.

Effects of Postannealing Process on the Properties of RuO2 Films and Their Performance As Electrodes in Organic Thin Film Transistors or Solar Cells

RuO(2) films were deposited on SiO(2) (300 nm)/N++Si substrates using radio frequency magnetron sputtering at room temperature. As-deposited RuO(2) films were annealed at different temperatures (100, 300, and 500 °C) and ambients (Ar, O(2) and vacuum), and the resulting effects on the electrical and physical properties of RuO(2) films were characterized. The effect of annealing atmosphere was negligible, however the temperature highly influenced the resistivity and crystallinity of RuO(2) films. RuO(2) films annealed at high temperature exhibited lower resistivity and higher crystallinity than as-deposited RuO(2). To investigate the possibility to use RuO(2) film as alternative electrodes in flexible devices, as-deposited and annealed RuO(2) films were applied as the source/drain (S/D) electrodes in organic thin film transistor (OTFT), catalytic electrodes in dye sensitized solar cell (DSSC) and as the hole-injection buffer layer (HIL) in organic photovoltaic (OPV). Except for OTFTs (μ ≈ 0.45 cm(2)/(V s) and on/off ratio ≈ 5× 10(5)) with RuO(2) S/D electrodes, the DSSC and OPV (3.5% and 2.56%) incorporating annealed RuO(2) electrodes showed higher performance than those with as-deposited RuO(2) electrodes (3.0% and 1.61%, respectively).

Printed metal electrode for flexible devices

We developed the novel pressure-annealing method for fabricating printed low-work function metal patterns and printed metal alloy patterns. The printed diode having various rectification properties was successfully produced by using the printed metal alloy electrode pressure-annealed.