Photoelectrochemical currents and potential distribution at the semiconductor/electrolyte interface for an electrochemical semiconductor solar energy converter have been analysed. Reactions involving minority and majority charge carriers in semiconductors and intermediate stages of electrocatalytic reactions involving electronic surface states were taken into account. The efficiency of semiconductor electrodes exposed to concentrated sunlight has been studied, and ways of increasing the photoconverter efficiency by the chemical modifications of the electrode surface have been considered for gallium arsenide and A(II)B(VI)-type compounds. Characteristics of the cells of solar batteries are given.