Chemical and electrochemical stability of WO3 electrochromic films in liquid electrolytes

Chemical and electrochemical stability of thermally evaporated amorphous films of WO₃ on conductive glass substrates have been studied in various electrolytes in order to determine the intrinsic lifetime or WO₃-based dis-play devices. The thickness loss of the WO₃ films measured under storage conditions in the glycerin-H₂SO₄ (10 : 1) mixture was a linear function of time for devices held at 50? C with a dissolution rate of 20 –25 å/day. Under cycling at room temperature an average dissolution rate of about 18 å/day was observed during the first 30 days at 0.5 Hz and 40 % con-trast [defined as 100 (B_colored - B_bleached / B_bleached) where B = brightness]. After that time the dissolution rate increased and the WO₃ film began to crumble. The dissolution rate of WO₃ has also been meas-ured in various non-aqueous solvents. The electrochemical response of WO₃ in the various electrolytes has been investigated.