Electrochromic Performance and Mechanism of Noncrystalline NiO_x H_y Thin Films Fabricated by Electrochemical Deposition
电化学沉积非晶NiO_xH_y膜的电致变色特性及其机理

The electrochromic(EC) properties of the electrochemically deposited NiO x H y thin films on glass substrates coated with SnO 2 thin films were studied. The coloring and bleaching transmission rate C t(which is the ratio of coloring light transmission density I c to bleaching light transmission density I b) is found to be 1/10 in the visible spectrum. In KOH electrolyte, the EC process is just the insertion and extraction of a proton or H +. OH - only provides an oxidation and redoxation environment related to coloring/bleaching process. The insertion of H + and its sequential filling the Ni vacancy will cause Ni 3+ to turn into Ni 2+ . The reduction of Ni 3+ then leads to the increase of light absorbance.It is because that the d energy level splits into t 2g and e g energy levels in the octahedral crystal field of NiO 6. The insertion of H + makes t 2g energy level of Ni 3+ occupied by electronics and then transparent.On the contrary, the extraction of H + causes t 2g energy level to lose some electronics and form Ni 3+ , resulting in the increase of light absorbance.