In our calculations, we only consider the charge generated by light and ignored the electrons generated by dopingtheir populations will be low at the surface of an n-type semiconductor. As a test of the importance of recombination, we introduce traps with a concentration of 110 2. Experimentally, hole absorbance as a function of light intensity increases much faster than the corresponding photocurrent, indicating that there is hole accumulation in the sample overall that is not predicted by the simulations. In addition, a higher light intensity than required in the experiment is needed for the transfer of holes from the bulk to the surface for chemical reactions because the bulk hole populations have to build up. The calculations predict an intensity-independent regime at high light intensities that is not observed experimentally. The reason for measurements of higher hole concentrations than are predicted by the calculations must be connected to sample properties but how is not clear.