Photovoltaically Self-Charging Battery

For many low-power applications, solar cells are used as an environmentally friendly power supply. In order to provide electrical power also in the absence of solar radiation, we invented a device which unifies both a solar cell and a rechargeable battery in one unit. The main components are a photoactive layer on a charge-storage layer. Thus, this new device represents a flat battery, which charges itself on illumination. In principle it can be produced cheaply, e.g. , by screen printing. The characteristics of charging and discharging are presented with special consideration of the variation of light intensity and ion concentration in the electrolyte. A relatively high reverse reaction at the electrode still takes place. After charging for 1 h under an illumination of 1000 W/m 2 , the first samples yielded 1.8 C/cm 2 when discharged in the dark. © 2002 The Electrochemical Society. All rights reserved.