Surface photovoltage interface recombination

If c = 0, then VJ,h gives a measure of the flat-band potential provided r/re(i()x is known. In fact, this formula is very rarely obeyed in practice and deviations are both common and complex. Detailed theories of the potential distribution at the semiconductor-electrolyte interface have been presented, based on photovoltage measurements, but immense care needs to be taken in the interpretation of the photovoltage since kinetic effects apparently play a major role. This is especially true if surface recombination plays an important role [172]. 

The electrons are detected as photocurrent in the external circuit. This shortcompetition between hole transfer across the interface (the Faraday reaction) and electron-hole recombination in the bulk semiconductor and at the surface of the electrode. Under open-circuit conditions no photocurrent can flow in the external circuit. The Fermi level in the semiconductor is raised with respect to that in solution and a photovoltage is established. In the limiting case at high light intensity, the energy bands become flat (Fig. lb). The maximum photovoltage is determined by the difference in Fermi level under flat band and equilibrium conditions. Clearly,... 

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