Photonenhanced thermionic emission solar energy converter is a new highly efficient solar energy utilization technologies. An exponential doping GaAs material was presented as the cathode of photonenhanced thermionic emission solar converter. The conversion efficiencies of the photonenhanced thermionic emission solar devices with exponential doping GaAs were theoretically analyzed by using the energybalance and diffusiondriftemission models. The results show that exponential doping GaAs prominently enhances photonenhanced thermionic emission conversion, and the efficiency of photonenhanced thermionic emission solar converters with exponential doping GaAs cathodes is a monotonically increasing function of sun concentration and a monotonically decreasing function of cathode surface recombination velocities. The efficiency of the converter can reach 30% at a flux concentration larger than 200 suns and surface recombination velocities maintained at fewer than 104 cm/s.