Electrochromic medium capable of producing a pre-selected color

Abstract

An improved electrochromic device, the device incorporating an electrochromic medium that comprises at least three electroactive materials having absorption spectra that add together such that the color of the electrochromic medium can be pre-selected by individually choosing the concentrations of the at least three electroactive materials. The electrochromic medium generally maintains the pre-selected perceived color throughout its normal range of voltages when used in an electrochromic device. The at least three electroactive materials include at least one electrochemically reducible material (cathodic material), at least one electrochemically oxidizable material (anodic material) and at least one additional electroactive material which may be either an anodic or cathodic material. Thus, there are always three electroactive materials present in the medium, with at least two either being anodic or cathodic materials. The pre-selected color may be chosen from a wide variety of colors and may be, for example, red, orange, yellow, green, blue, purple. For electrochromic mirrors for motor vehicles, a presently preferred color is gray.