Tailoring the electrochromic properties of devices via polymer blends, copolymers, laminates and patterns

The ability to tune colour constitutes an important goal in the design of electrochromic devices. The majority of single electrochromic materials, whether inorganic or organic have a very narrow spectral colour change, however. Complex colours such as browns and tans that mimic natural vegetation and soils are not inherent to these materials. We have explored several strategies to achieve these colours including the use of copolymers that contain two distinct moieties, blends of polymers that have different colour changes, laminating two different polymers on the working electrode, and using fine patterns of two different materials to confuse the eye. We have constructed solid state electrochromic devices using ITO/Mylar substrates, a solid polymer electrolyte, a V2O5 counterelectrode and working electrodes that were made via one of the four methods outlined above. The colour changes of these devices were measured using spectrocolourimetry conforming to the CIE standard. The colour changes observed were similar to those of natural vegetation and soils.