A simulation of alternating‐current thin‐film electroluminescent device operation with positive space charge present in the phosphor layer of the device is presented. The simulation is based on modeling the space‐charge distribution using a single‐sheet charge model. The simulation is performed for two cases of space‐charge creation: by impact ionization of deep levels in the phosphor or by field emission from traps in the phosphor. Results of the simulation show that space‐charge creation by either mechanism is capable of causing overshoot in both capacitance‐voltage and internal charge‐phosphor field (Q‐Fp) plots. ©1995 American Institute of Physics.