A method is described for modeling charge transfer and recombination across functionalized Si(111) photoelectrodes using a 1D solid state drift-diffusion device simulation - wxAMPS. To demonstrate the approach, the effect of charge transport mechanisms on the photoelectrochemical performance of hydrogen and methyl-terminated Si(111) electrodes was analyzed. When contacted with electrolyte, prior literature proposed three charge transfer mechanisms that can affect the performance of functionalized surfaces: a shift in interfacial dipole, a change in surface recombination, or Fermi level pinning. By modeling all three processes using wxAMPS, a shift in interfacial dipole of -0.35 +/- 0.05 eV between hydrogen and methyl-terminated Si(111) was concluded to be the predominant effect in these electrodes. This verifies prior hypotheses while predicting a more accurate value of the shift in interfacial dipole than previous theoretical treatment and experimental interpretations. (C) 2016 The Electrochemical Society. All rights reserved.