Solid-state redox diode composed of an electropolymerized metallocene layer and a polymer electrolyte layer containing a redox couple in a mixed-valent state

Abstract

Redox bilayer devices, SnO₂/poly-Cc⁺/PEO–Li⁺, Fc^+/O/SnO₂; SnO₂/poly-Cc⁺/PEO–Li⁺, DDQ^O/–/SnO₂; SnO₂/poly-Cc⁺/PEO–Li⁺, TCNQ^O/–/SnO₂ and SnO₂/poly-Fc/PEO–Li⁺, TCNQ^O/–/SnO₂ have been constructed and their i vs. ΔE characteristics investigated. Poly-Cc⁺, poly-Fc and PEO represent polymers formed by electro-chemical reduction of 1,1′-bis(1-chloro-2-formylvinyl)cobaltocenium salt and 1,1′-bis(chloromethyl)ferrocene, and cross-linked poly(ethylene oxide), respectively. All the devices show diode-like i vs. ΔE characteristics, which relate to the difference in redox potentials between the two layers, ΔE°′. The i vs. ΔE curves obtained can be analysed by a simple model assuming that the diffusion-controlled electron transfer at the interface of the layers and/or the charge diffusion in the polymer electrolyte layer limit the electron conduction rate.