Electrochemical Solar Cell Based on the d‐Band Semiconductor Tungsten‐Diselenide

In a search for corrosion resistent electrode materials for electrochemical solar cells the covalent, layered semiconductor WSe2, has been investigated. Its photoactivity in the visible spectral region (band gap 1.57 eV) involves d‐d electron transitions which do not lead to an immediate photocorrosien. An energetically favourable energy band position makes it possible to operate p‐type material as photocathodes for energy conversion. Photocell outputs in the order of 15 mA/cm2 and 0.5 V were obtained in 100 mW/cm2 illumination (Xenon‐lamp). It is shown that the produced photovoltage is not systematically dependent on the redox potential of the redox agents but influenced by their chemical reactivity due to a specific interaction with the electrode surface.