We conduct 2-D simulations of device structures typical of electron-beam-induced current (EBIC) imaging and solar cell structures for p-type CdTe absorber layers with charged grain boundaries. A large signal enhancement is found near depleted (positively charged) grain boundaries for EBIC simulation, but in contrast with previous claims, solar cell performance drops. In contrast, little EBIC contrast is seen, but the cell performance improves when accumulated (negatively charged) grain boundaries are introduced. We explore the impact of doping level, lifetimes, and grain boundary charge to provide insight for design of improved thin film solar cells.