Solution-Deposited Solid-State Electrochromic Windows

Wei Cheng,Marta Moreno-Gonzalez,Ke Hu,Caroline Krzyszkowski,David J Dvorak,David M Weekes,Brian Tam,Curtis P Berlinguette

doi:10.1016/j.isci.2018.11.014

Abstract

SummaryCommercially available electrochromic (EC) windows are based on solid-state devices in which WO3 and NiOx films commonly serve as the EC and counter electrode layers, respectively. These metal oxide layers are typically physically deposited under vacuum, a time- and capital-intensive process when using rigid substrates. Herein we report a facile solution deposition method for producing amorphous WO3 and NiOx layers that prove to be effective materials for a solid-state EC device. The full device containing these solution-processed layers demonstrates performance metrics that meet or exceed the benchmark set by devices containing physically deposited layers of the same compositions. The superior EC performance measured for our devices is attributed to the amorphous nature of the NiOx produced by the solution-based photodeposition method, which yields a more effective ion storage counter electrode relative to the crystalline NiOx layers that are more widely used. This versatile method yields a distinctive approach for constructing EC windows.

Highlights

Electrochromic (EC) windows undergo changes in light transmittance in response to an applied voltage, enabling the dynamic control of daylight and solar heat passing through buildings (Granqvist, 2006, 2012a; Runnerstrom et al, 2014)
A solution of WCl6 in 2-propanol was spin-cast onto a fluorine-doped tin oxide (FTO) substrate and the resultant precursor film was irradiated with UV light to form a metal oxide film
The X-ray diffraction (XRD) pattern of the as-prepared NiOx films showed a broad reflection centered at 2q = 18 indexed to the (001) facets of a-Ni(OH)2 (Smith et al, 2016), together with the reflections corresponding to the FTO substrate (Figure S3)

Summary

Introduction

Electrochromic (EC) windows ( known as smart or dynamic windows) undergo changes in light transmittance in response to an applied voltage, enabling the dynamic control of daylight and solar heat passing through buildings (Granqvist, 2006, 2012a; Runnerstrom et al, 2014) This technology can provide both indoor thermal and visual comfort for building occupants while improving building energy efficiency by as much as 20% (Granqvist, 2012a). A significant fraction of the cost is imbedded in the vacuum environment required to sputter EC window layers This process can require a substantial capital outlay, and the long residence times needed to fabricate the key layers on rigid substrates preclude rapid throughput (Garg et al, 2005). These factors present the impetus to develop solution-based deposition methodologies to reduce the costs associated with fabricating EC windows (Barile et al, 2017; Cai et al, 2016a; Llordes et al, 2016)

Methods

Results

Conclusion