Abstract
The electrochromic performance of all solid‐state cells employing phosphotungstic acid and phosphomolybdic acid is reported. These cells employ SnO2 as the viewing electrode and graphite as the back electrode. Diffuse reflectivity changes of ∼50% are readily achieved in ∼10 msec. The cells, in the bleached state, can be made white to red, and become black in the colored state.