Electrochemical studies of the electron states of disordered electrochromic oxides

In this paper, we show that electrochemical quasi-steady state potential curves of disordered tungsten, titanium, cerium and iridium oxides exhibit fine structure in striking agreement with the density of electronic states, as obtained from ab initio calculations for the crystalline counterparts. The ability to probe the electronic structure by our electrochemical technique is restricted to disordered non-metallic materials. It is highly probable that the probed electronic states are required to be localized, in order for the technique to give a good picture of their density. The electrochemical density of states is often smaller than the computed one due to kinetic effects, i.e. very slow relaxations of the charge carriers. By combining electrochemical and electrical conductivity measurements for the case of tungsten oxide, we have verified the localized character of the probed states and estimated their localization radius.