PROBLEM TO BE SOLVED: To eliminate conventional disadvantages, and to improve the stability of the performance of a cell in the course of time as a function of an operating temperature. ;SOLUTION: A cell including a photoanode composed of at least one polycrystalline titanium dioxide layer on a conductive substrate, a counter-electrode and an electrolyte positioned between these electrodes, at least one of the electrodes being transparent or translucent is provided. The electrolyte includes an oxidation-reduction system which is liquid at room temperature. A first species of a pair constituting the oxidation-reduction system advantageously is composed of an electrochemically-active salt having a melting point below room temperature, and optionally dissolved in at least one electrochemically-inactive salt also having a melting point below room temperature. ;COPYRIGHT: (C)2009,JPO&INPIT