PHOTOPOTENTIAL OUTPUT OF ELECTROCHEMICAL SOLAR-CELLS BASED ON LAYER-TYPE D-BAND SEMICONDUCTORS

A comparative study of molybdenum- and tungsten-dichalcogenides in contact with various redox electrolytes revealed that in absolute values as well as in relation to the energy gap, n-type WSe//2 is producing the largest photopotential output. Addition of small quantities of iodide can increase the photopotential output in presence of redox systems with lower redox potential by up to 0. 1 Volt. This gives further evidence for the specific photochemical surface activity of iodide on layer-type electrodes and is an example for the influence of surface states on the efficiency of energy conversion. The higher photopotential output of WSe//2 as compared to that of MoSe//2 (maximum value I** minus /I//2:0. 56 Volt) is explained in terms of a negative shift of the conduction band edge. With respect to the efficiency of electrochemical solar energy conversion WSe//2 is considered to be the most promising compound among layer-type d-band semiconductors.