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

Redox bilayer devices, SnO2/poly-Cc+/PEO–Li+, Fc+/O/SnO2; SnO2/poly-Cc+/PEO–Li+, DDQO/–/SnO2; SnO2/poly-Cc+/PEO–Li+, TCNQO/–/SnO2 and SnO2/poly-Fc/PEO–Li+, TCNQO/–/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.