A novel photo‐electrochemical cell based on a combined principle of photogalvanic and photovoltaic effects is proposed and tested. the principal element of the cell consists of a pigmented membrane separating two aqueous solutions, one of which contains thionine dye and ferrous ions. the photo‐e.m.f. generated across the cell is equal to the sum of the voltages derived from the photogalvanic and photovoltaic processes. the feasibility of such a photo‐galvano‐voltaic device for light transduction has been demonstrated. Copyright © 1978 John Wiley & Sons, Ltd.