The influence of edges on the performance of small-area solar cells is determined using a modified commercial, finite-element software package. The n+/p mesa device is modeled as having a sub-oxide layer on the edges, which acquires positive charges that result in development of an electric field within the device. Our computer simulations include generation/recombination at the diode edges as well as the influence of light on the recombination characteristics of the edges. We present a description of our model, dark and illuminated characteristics of devices with various surface charge concentrations, and the dynamics of carrier generation/recombination. The influence of edge geometry on diode performance is determined.