Technology Advancements to Lower Costs of Electrochromic Window Glazing

An Electrochromic (EC) Window is a solar control device that can electronically regulate the flow of sunlight and heat. In the case of the SageGlass{reg_sign} EC window, this property derives from a proprietary all-ceramic, intrinsically durable thin-film stack applied to an inner surface of a glass double-pane window. As solar irradiation and temperatures change, the window can be set to an appropriate level of tint to optimize the comfort and productivity of the occupants as well as to minimize building energy usage as a result of HVAC and lighting optimization. The primary goal of this project is to replace certain batch processes for EC thin film deposition resulting in a complete in-line vacuum process that will reduce future capital and labor coats, while increasing throughput and yields. This will require key technology developments to replace the offline processes. This project has enabled development of the next generation of electrochromic devices suitable for large-scale production. Specifically, the requirements to produce large area devices cost effectively require processes amenable to mass production, using a variety of different substrate materials, having minimal handling and capable of being run at high yield. The present SageGlass{reg_sign} production process consists of two vacuum steps separated by an atmospheric process. This means that the glass goes through several additional handling steps, including venting and pumping down to go from vacuum to atmosphere and back, which can only serve to introduce additional defects associated with such processes. The aim of this project therefore was to develop a process which would eliminate the need for the atmospheric process. The overall project was divided into several logical tasks which would result in a process ready to be implemented in the present SAGE facility. Tasks 2 and 3 were devoted to development and the optimization of a new thin film material process. These tasks are more complicated than would be expected, as it has been determined in the past that there are a number of interactions between the new material and the layers beneath, which have an important effect on the behavior of the device. The effects of these interactions needed to be understood in order for this task to be successful. Tasks 4 and 5 were devoted to production of devices using the novel technology developed in the previous tasks. In addition, characterization tests were required to ensure the devices would perform adequately as replacements for the existing technology. Each of these tasks has been achieved successfully. In task 2, a series of potential materials were surveyed, and ranked in order of desirability. Prototype device structures were produced and characterized in order to do this. This satisfied the requirements for Task 2. From the results of this relatively extensive survey, the number of candidate materials was reduced to one or two. Small devices were made in order to test the functionality of such samples, and a series of optimization experiments were carried out with encouraging results. Devices were fabricated, and some room temperature cycling carried out showing that there are no fundamental problems with this technology. This series of achievements satisfied the requirements for Tasks 3 and 4. The results obtained from Task 3 naturally led to scale-up of the process, so a large cathode was obtained and installed in a spare slot in the production coater, and a series of large devices fabricated. In particular, devices with dimensions of 60-inch x 34-inch were produced, using processes which are fully compatible with mass production. Testing followed, satisfying the requirements for Task 5. As can be seen from this discussion, all the requirements of the project have therefore been successfully achieved. The devices produced using the newly developed technology showed excellent optical properties, often exceeding the performance of the existing technology, equivalent durability results, and promise a significantly simplified manufacturing approach, thereby suggesting higher yields as a result of less handling, and therefore lower costs