Scalable synthesis of improved nanocrystalline, mesoporous tungsten oxide films with exceptional electrochromic performance

Abstract

a b s t r a c tTemplated sol gel chemistry provides a versatile approach to introduce order and porosity into nanostructured materials. However conventional evaporation induced self assembly techniques are not easily scaled to produce films with sufficient thickness over large areas at the throughput required by electrochromic windows. Here we demonstrate that the principles of sol gel chemistry may be deployed using ultrasonic spray deposition (USD) for scalable synthesis of nanocrystalline WO 3 films with unrivaled electrochromic performance. Systematic manipulation of sol chemistry enabled the production of mesoporous films with high specific surface area (4 100 m 2 /g), mean pore sizes of $ 5 nm, and narrow pore size distributions. Film thickness is found to be proportional to the sol concentration and number of spray passes, and various combinations are shown to produce films capable of modulating 498% of incident solar radiation in the visible spectrum (450-900 nm). Elimination of haze enables full transmission in the bleached state, while the broadband coloration is attributed to the exceptionally high charge density ( 4120 mC/cm 2 ). The materials have good switching speeds which improve with specific surface area, and the long term durability is promising.

Electrochromic materials and devices for energy efficiency and human comfort in buildings: A critical review

“…Low-cost manufacturing and long-term durability are keys to successful products and, as discussed in this article, web-coating can be implemented to create light-weight, rugged EC devices in the form of large sheets or on a roll suitable for glass lamination and incorporation in glazing. Reactive DC magnetron sputtering appears to be a preferred deposition technology, but other options, for example based on sol-gel deposition [168] or inkjet printing [169], may be used. In contrast with many other "green" technologies, electrochromism does not rely on "critical" rare-earth elements with questionable availability [170].…”

Electrochromic Properties of Electrospun Fibers Based on Bis‐Thiomethylcyclohexanone Derivatives

“…where η is the coloration efficiency (CE), Tb is the transmittance of the layer in bleached state and Tc is the transmittance of the layer in the colored state . The calculated coloration efficiency of the hybrid fibers based on PPTMC ‐PMMA is found to be 207.27 cm 2 /C whereas higher coloration efficiency is obtained for the hybrid fibers based on CPPTMC‐ PMMA (273.31 cm 2 /C).…”

PEDOT/WO3 Hybrid Nanofiber Architectures for High Performance Electrochromic Devices

“…where Tb and Tc refer to the transmittance of the layer in its bleached and colored states, respectively, and I is the current density [30]. An EC material with a high coloration efficiency can provide a large transmittance mod- ) [17,18].…”