Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userHybrid electrochromic device with Tungsten oxide (WO3-x) and nafion membrane: performance with varying tungsten oxide thickness
71
0
0.0
(
0
)
Added by
Udaykumar Khanapuram
Publication date
2016
fields
Physics
and research's language is
English
Ask ChatGPT about the research
No Arabic abstract
Electrochromic devices, which dynamically change color under the applied potential, are widely studied because of its wide range of applications such as energy-efficient smart windows, rear view mirrors and display devices etc. In this study we are reporting four layer electrochromic device based on tungsten oxide as a electrochromic layer and nafion membrane as a ionic conducting layer. Nafion membranes are generally used in fuel cell applications because of its high ionic conductivity and high optical transparency which is suitable for electrochromic device to attain higher efficiencies. We have prepared an electrochromic device by sandwiching ITO coated glass and WO3 coated ITO thin film between nafion membrane. The overall structure of the device is Glass/ITO/WO3/Nafion/ITO/Glass. We deposited tungsten oxide thin films with different thickness on ITO coated glass substrate at room temperature by using reactive DC Magnetron sputtering and we studied the performance of the electrochromic device with the function of thickness. We have observed that electrochromic efficiency is increasing with increase in the tungsten oxide layer thickness. The efficiency of the device increased from 24.8 cm2/C to 184.3 cm2/C.
rate research
Read More
Electrochromic materials change color reversibly by applying an external DC voltage. One among the many emerging application of electro-chromics is the smart windows. The coloration efficiency, the optical colour modulation and the cyclability are the factors that bench mark the device. Tungsten oxide (WO3-x) is versatile material and reactive DC magnetron sputtering (with argon as sputter gas) technique is common for electro-chromics. In the present communication we have prepared tungsten oxide thin films by reactive DC magnetron sputtering technique (at room temperature 300 K) using Neon as the sputter gas. The thickness of the WO3 thin films are varied from 190 nm to 712 nm. These WO3 thin films are subjected for electrochemical measurements with three electrode electrochemical cell in presence of 1M HCl, 1M Li2SO4 aqueous electrolyte and we have prepared a solid state electrochromic device with nafion thin film. The highest coloration efficiency of the neon sputtered WO3 is observed as 187.9 cm2/C by lithium intercalation.
In this work, we investigate the correlation between morphology, composition, and the mechanical properties of metallic amorphous tungsten-oxygen and amorphous tungsten-oxide films deposited by Pulsed Laser Deposition. This correlation is investigated by the combined use of Brillouin Spectroscopy and the substrate curvature method. The stiffness of the films is strongly affected by both the oxygen content and the mass density. The elastic moduli show a decreasing trend as the mass density decreases and the oxygen-tungsten ratio increases. A plateaux region is detected in correspondence of the transition between metallic and oxide films. The compressive residual stresses, moderate stiffness and high local ductility that characterize compact amorphous tungsten-oxide films make them promising for applications involving thermal or mechanical loads. The coefficient of thermal expansion is quite high (i.e. 8.9 $cdot$ 10$^{-6}$ K$^{-1}$), being strictly correlated to the amorphous structure and stoichiometry of the films. Under thermal treatments they show a quite low relaxation temperature (i.e. 450 K). They crystallize into the $gamma$ monoclinic phase of WO$_3$ starting from 670 K, inducing an increase by about 70% of material stiffness.
The band structure, density of states, and the Fermi surface of a tungsten oxide WO$_{2.9}$ with idealized crystal structure (ideal octahedra WO$_6$ creating a square lattice) is obtained within the density functional theory in the generalized gradient approximation. Because of the oxygen vacancies ordering this system is equivalent to the compound W$_{20}$O$_{58}$ (Magn{e}li phase), which has 78 atoms in unit cell. We show that 5$d$-orbitals of tungsten atoms located immediately around the voids in the zigzag chains of edge-sharing octahedra give the dominant contribution near the Fermi level. These particular tungsten atoms are responsible of a low-energy properties of the system.
We investigate the electronic structure of tungsten ditelluride (WTe$_2$) flakes with different thicknesses in magneto-transport studies. The temperature-dependent resistance and magnetoresistance (MR) measurements both confirm the breaking of carrier balance induced by thickness reduction, which suppresses the `turn-on behavior and large positive MR. The Shubnikov-de-Haas oscillation studies further confirm the thickness-dependent change of electronic structure of WTe$_2$ and reveal a possible temperature-sensitive electronic structure change. Finally, we report the thickness-dependent anisotropy of Fermi surface, which reveals that multi-layer WTe$_2$ is an electronic 3D material and the anisotropy decreases as thickness decreases.
TiO$_2$ and WO$_3$ are two of the most important earth-abundant electronic materials with applications in countless industries. Recently alloys of WO$_3$ and TiO$_2$ have been investigated leading to improvements of key performance indicators for a variety of applications ranging from photo-electrochemical water splitting to electrochromic smart windows. These positive reports and the complexity of the ternary W-Ti-O phase diagram motivate a comprehensive experimental screening of this phase space. Using combinatorial thermal oxidation of solid solution W$_{1-x}$Ti$_{x}$ precursors combined with bulk and surface analysis mapping we investigate the oxide phase formation and surface passivation of tungsten titanium oxide in the entire compositional range from pure WO$_3$ to TiO$_2$. The system shows a remarkable structural transition from monoclinic over cubic to tetragonal symmetry with increasing Ti concentration. In addition, a strong Ti surface enrichment is observed for precursor Ti-concentrations in excess of 55 at.%, resulting in the formation of a protective rutile-structured TiO$_2$ surface layer. Despite the structural transitions, the optical properties of the oxide alloys remain largely unaltered demonstrating an independent control of multiple functional properties in W$_{1-x}$Ti$_{x}$O$_{n}$. The results from this study provide valuable guidelines for future development of W$_{1-x}$Ti$_{x}$O$_{n}$ for electronic and energy applications, but also novel engineering approaches for surface functionalization and additive manufacturing of Ti-based alloys.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
