SBIR-STTR Award

To attain the potentially vast energy saving and environmental benefits of electrochromic (ec) smart windows, an economically and technically viable manufacturing technology must be achieved. The sol-gel technique offers distinct advantages over the commonly used vapor deposition techniques as a core film deposition method for these multilayer structures. All inorganic lithium-based solid state smart window devices have been fabricated on glass substrates using the sol-gel dip coating method to grow the ion conductor layer and other layers of this device. However, conventional dip coating also has its limitations in a production environment. Phase i will combine the sol-gel technique with squeeze-roll coating as an alternate coating technique which combines the advantages of dip coating with the potential benefits of a continuous line suitable for mass production of the multilayer smart window structures. The specific objective in phase i is to test the feasibility of using this "roll-gel" coating to obtain films of an ec electrode material on up to 18 in, wide glass substrates which are sufficiently thin and uniform in thickness to provide good ec device performance. For phase i, the films will be the ec material tungsten trioxide. A further objective is to design a roll-gel continuous line for construction and development in phase ii.

Switchable electrochromic (EC) glazings have potential use in a vast number of energy-saving smart window applications. For EC smart windows to achieve full commercial potential, manufacturing technology must be developed that can cost-effectively produce large-area, functional EC films uniformly. Previously, an all-ceramic, thin-film EC device was developed that combines durable materials and device structure with cost-effective manufacturing techniques. An innovative "roD-gel" approach, potentially useful for three EC layers, combines novel sol-gel film chemistry with the adaptation of a highthroughput web coating process. Phase I provided confirmation of the initial technical feasibility of using this roll-gel coating process for depositing a tungsten oxide (W03) electrochromic electrode (ECE) layer on glass. With three different stabilized, non-aqueous precursor solutions and a standard dip coating procedure, 180 nm W03 films (6 dips required) were made. Except for a slight bleached-state transmission loss, EC devices with dip coated W03 films compared well to those with sputtered W03. Modified solution composition, synthesis, and post-coating treatment procedures should remedy this loss. Also developed was a thicknesslcolor chart to correlate observed film color with thickness and uniformity. In this project, a 24 inch roll-gel coating system will be specified and procured, and the coatings will be parametrically developed so that a well-characterized, statistically proven, manufacturing process exists for depositing the ion conductor (IC), the ECE and, possibly, the counter electrode (CE) layers. The work plan is defined in 3 parts: 1) perform more engineering studies to complete the roll-gel system specifications for the desired film thicknesses, 2) work with a qualified equipment supplier to design and build a 24 inch wide roll-gel coating system equipped with glass transport and curing capabilities, and 3) fabricate functional 10 inch by 12 inch EC devices with optimized roll-gel coated films and quantify projected manufacturing costs. Anticipated Results /Potential Commercial Applications as described by the awardee:If successful, the Phase II should provide the needed manufacturing technology and economics to produce commercially viable EC smart windows through the development of a cost-effective roll-gel coating system. While the focus will be on specific opportunities associated with architectural glass markets (residential and commercial), EC smart windows have the potential to spawn a wide range of advanced applications and new opportunities in architectural, transportation, and specialty optical control markets.