Electrochromism within Transition‐Metal Coordination Complexes and Polymers

Transition-metal complexes often possess multiple well-defined redox processes and the electronic absorptions are largely dependent on the redox states. This is one of the main reasons why transition-metal complexes are appealing for electrochromism. In order to develop solid-state devices for practical use, electrochromic materials must be deposited onto electrodes as thin films. The sections in this chapter are arranged according to the difference in film-forming methods. The electrochromism of complexes as small molecules dissolved in solution is briefly mentioned. The chapter talks about electropolymerisation, which is a very useful means for preparing thin films. The difference between them is the mechanism of the electropolymerisation: reductively versus oxidatively initiated. Multilayer films simply prepared by self-assembly on electrode surfaces or adsorbing on semiconductor surfaces are discussed. The chapter explains the electrochromism in thin films prepared by spin coating or drop casting. Finally, a comparison of these film-forming methods for electrochromism is discussed.