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Inert Metal Transparent Conducting Contact for Electroplating Electrochromic Devices

National Renewable Energy Laboratory

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Technology Marketing Summary

Electrochromic devices are able to switch between a transparent state and a tinted state when a voltage is applied. These devices enable building owners to control the amount of heat and sunlight entering through windows electronically. While the market for electrochromic glass is relatively new, it amounted to nearly $1B in 2017, and is expected to more than double by 2022 growing at a CAGR of 15.2% over that time according to research firm, Research and Markets. In addition to building windows electrochromic devices can be used as partitions, skylights, and windows for automobiles.

Although this is a promising technology, its use has so far been limited. Unfortunately, traditional electrochromic devices that change to a tinted state capture solar radiation and re-emit it into the window as heat (like all tinted windows). This challenge has been mitigated through the development of reflective electrochromic devices that reject energy at the window rather than absorb energy and re-distribute it as heat.


Researchers at NREL have created a lithium-based switchable thin film that can act as a reflective surface when a small voltage is applied but is transparent in the absence of electricity. Transparent, electrically conductive contact layers are required to apply the required drive voltages in these devices. In addition to being expensive to manufacture, traditional transparent conducting oxides (TCOs) which are used in other electrochromic applications react with lithium and prevent switching of the device. The transparent contact developed at NREL is inert to metallic lithium, allowing devices to switch between reflective and transparent states. Preliminary results indicate an approximate energy savings of 43% for reflective as compared to traditional electrochromic windows. The reduction of re-emitted heat from the device may also reduce challenges with retrofitting a product to an existing window such as in a film.

  • Reduces air conditioning costs
  • Controls building lighting while reducing lighting costs
  • Can be retrofitted to existing windows
  • Flexible aesthetics
Applications and Industries
  • Electrochromic windows
  • Building window tinting
  • Automobile windows
  • Batteries
Patents and Patent Applications
ID Number
Title and Abstract
Primary Lab
Patent 9,880,440
Electrochromic devices and related products and methods
An electrochromic device may be switchable between a transparent state and at least one reflective state. A lithium-containing reflective feature may form when the electrochromic device is switched from the transparent state to the reflective state. Various products and methods may involve the electrochromic device.
National Renewable Energy Laboratory 01/30/2018
Technology Status
Technology IDDevelopment StageAvailabilityPublishedLast Updated
NREL ROI 13-20ProposedAvailable02/22/201802/15/2018

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To: Erin Beaumont<>