Multi‐electron transfer in composite phthalocyanine thin films: structure and electrochromic properties

Both sequentially deposited double‐layered and codeposited composite thin films were prepared by using two kinds of phthalocyanines. The structure and the electrochromic property of these thin films were compared with those of simple phthalocyanine films. The structures of the films were analyzed by scanning electron microscopy (SEM), X‐ray diffrction (XRD) and electron spin resonance (ESR) spectra. From the viewpoint of morphology and crystallinity, codeposited thin films have the same structure as the simple one, having sharp peaks at ca. 2θ=7.0° in the XRD pattern and narrow crystal grains in SEM photographs. ESR measurements have revealed that phthalocyanine molecules disperse very well in the codeposited thin films in a molecular level in comparison with the physical mixture of phthalocyanine powders. This high dispersibility of the molecules in the codeposited thin films can play a role to improve the reversibility in the electrochromism. Thus, the reversibility of the phthalocyanine, which shows irreversible electrochromism in the simple film form, can be improved by the codeposition with another phthalocyanine with reversible electrochromism. In contrast, sequentially deposted double‐layered thin film gives completely different results. The electrochromism of the double‐layered film depends on the property of the simple phthalocyanine thin film which is in contact with the substrate.