Electrochromic Devices Deposited on Low-Temperature Plastics by Plasma-Enhanced Chemical Vapor Deposition

Robbins, Joshua ; Seman, Michael

CMD Research, LLC, Golden, CO

关键词: Optical Properties;    Aluminium;    Energy Consumption;    Chemical Vapor Deposition;    Plastics;   

DOI  :  10.2172/850233
RP-ID  :  None
RP-ID  :  FG36-04GO14328
RP-ID  :  850233

美国|英语

来源: UNT Digital Library

【 摘 要 】

Electrochromic windows have been identified by the Basic energy Sciences Advisory committee as an important technology for the reduction of energy spent on heating and cooling in residential and commercial buildings. Electrochromic devices have the ability to reversibly alter their optical properties in response to a small electric field. By blocking ultraviolet and infrared radiation, while modulating the incoming visible radiation, electrochromics could reduce energy consumption by several Quads per year. This amounts to several percent of the total annual national energy expenditures. The purpose of this project was to demonstrate proof of concept for using plasma-enhanced chemical vapor deposition (PECVD) for depositing all five layers necessary for full electrochromic devices, as an alternative to sputtering techniques. The overall goal is to produce electrochromic devices on flexible polymer substrates using PECVD to significantly reduce the cost of the final product. We have successfully deposited all of the films necessary for a complete electrochromic devices using PECVD. The electrochromic layer, WO3, displayed excellent change in visible transmission with good switching times. The storage layer, V2O5, exhibited a high storage capacity and good clear state transmission. The electrolyte, Ta2O5, was shown to functional with good electrical resistivity to go along with the ability to transfer Li ions. There were issues with leakage over larger areas, which can be address with further process development. We developed a process to deposit ZnO:Ga with a sheet resistance of < 50 W/sq. with > 90% transmission. Although we were not able to deposit on polymers due to the temperatures required in combination with the inverted position of our substrates. Two types of full devices were produced. Devices with Ta2O5 were shown to be functional using small aluminum dots as the top contact. The polymer electrolyte devices were shown to have a clear state transmission of 69% and a darkened state transmission 11%. These un-optimized devices compared well with commercially available products, which have a stated clear transmission of 59% and dark transmission of 4%. The PECVD oxides have displayed advantages over films produced by sputtering. The first advantage is that deposition rates were significantly higher than typical sputtering rates. Rates of 100 nm/min were achieved for WO3, and rates of 50 nm/min produced quality V2O5 and Ta2O5 films. Faster rates will produce a significant reduction in cost due to higher throughput. Another advantage was that films were less dense than those produced by sputtering as reported in the literature. This leads to high diffusion coefficients and fast switching times. Also less dense films have been shown to produce larger contrast ratios in WO3 and larger storage capacity in V2O5. From the data collected in this category 1 project we have shown that PECVD is feasible and beneficial for the deposition of working layers for electrochromic devices. These results and the lessons learned can be applied toward deposition on polymers and equipment scale-up in future work.