Construction of a ‘Sequential Potential Field’ by [Cu(pc)]/[Zn(pc)] double-layered Thin Film: Application to Electrochromic and Electroluminescent Devices

Abstract

‘Sequential potential field’ is a concept to produce a potential cascade by the organization of redox components, and to aim for an effective and vectorial electron and/or hole transfer. Construction of the sequential potential field is examined by double-layered thin film composed of two kinds of metallophthalocyanine having different oxidation potentials, i.e. copper phthalocyanine and zinc phthalocyanine. In the electrochromic device of double-layered metallophthalocyanine thin films, hole transfer can be controlled by the order of deposition, which suggests that the present system is suitable for the construction of a sequential potential field. Double-layered metallophthalocyanine thin films were also used as a hole transfer layer in all-solid organic electroluminescent devices. In the case of an indium-tin oxide/copper phthalocyanine/zinc phthalocyanine/tris(8-hydroxyquinoline)aluminum/ Mg - Ag device for electroluminescence, a high brightness of more than 4000 cd m−2 can be achieved. This double-layered hole transfer system is more effective than the corresponding single hole transfer system, which is due to the construction of a sequential potential field in the hole transfer layer.