Uniform and smooth tetraaniline electrochromic films were prepared directly by spreading its alcohol solution onto clean ITO at room temperature. Film thickness was controlled by tuning the solution concentrations and the areas of conducting glasses. Two pairs of reversible redox peaks were found in its cyclic voltammogram, which corresponded to the transformation of leucoemeraldine base (LB) to emeraldine salt (ES) and emeraldine salt (ES) to pernigraniline salt (PS), respectively. Meanwhile, the film color changed from light yellow to green and then to blue with the increasing of potential. Furthermore, it was found that the electrochromic properties of tetraaniline films were related to the type of electrolytes and film thickness. The tetraaniline electrochromic contrast decreased when the HCl electrolyte solution was replaced with HNO₃, H₂SO₄ and LiClO₄ solution, respectively. And with the increasing of film thickness, the electrochromic contrast enhanced but the response time prolonged. On the other hand, when the electrochromic films were prepared from camphorsulfonic acid-doped tetraaniline, it exhibited high contrast and fast switching speed simultaneously.

Key words: aniline oligomer, electrochromism, contrast, response time