Platinum islands 5–50 nm in size were deposited on n‐type single‐crystal silicon (n‐Si) wafers by reduction of hexachloroplatinic (IV) acid with hydrogen. Photoelectrochemical solar cells, made from such an n‐Si electrode coated with Pt islands, generated open‐circuit photovoltages as high as 0.63V, about 8% higher than those of normal p‐n junction Si solid solar cells. The ideality factor was estimated to be close to unity, and the dark saturation current density was estimated to be very low, or less, in accord with the above‐mentioned high . Though the obtained here is somewhat lower than the top data reported previously, the relation between the size of the metal island and has been further clarified. These results give further support to our recently proposed theory that the effective barrier height in a Pt‐island coated n‐Si electrode depends on the island size and can reach the equivalent of the bandgap for small islands. Also, a p‐type Si electrode coated with Pt islands in the same way as for the n‐Si electrode showed a good rectifying character and an efficient hydrogen evolving photocurrent in an acid solution.
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Ueda et al. (1989) studied this question.