Theoretical aspects of light activated semiconductor (SC) microdisk electrodes in redox electrolytes have been examined as a function of the dimensionless photon flux sigma and dimensionless bias potential Phi(bias). Dimensionless steady-state profiles for solid-state and solution phase species were obtained by solving self-consistently the transport equations and the electrostatic potential within the SC subject to the appropriate boundary conditions using COMSOL. Analyses of the results obtained revealed that for fixed sigma and small Phi(bias), the local dimensionless flux at the interface normal to the SC surface, J(Z)*(R,0), where R is the dimensionless radius normal to the axis of symmetry, is dominated by the oxidation process in the illuminated region (R <= 1) and by the reduction process in the dark area near the edge of the illuminated region. For large Phi(bias), however, the oxidation process dominates J(Z)*(R,0) everywhere along the interface. Agreeing with the phenomenon described in our earlier publication, the holes escape beyond R = 1, yielding, for very large values of Phi(bias) and sigma, a total current flowing through the dark area that can exceed that collected within the illuminated disk. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3462995] All rights reserved.