An investigation of the backwall MIS Schottky barrier solar cell model was made. This model incorporates the following factors which, for the most part, determine the behavior of the device: the short circuit current density, the MIS Schottky barrier junction behavior, and resistive losses. The study concentrated on the Al‐Al2O3‐GaAs‐metal structure. Practical energy conversion efficiencies are predicted for this structure for a variety of semiconductor properties ranging from best‐ to worst‐case conditions. Reflection losses are ignored assuming that the proper antireflective coating will minimize these losses. The study of the short circuit current density indicates that the structure must be that of a thin‐film semiconductor with maximum current occurring when the GaAs thickness is in the 500‐A˚ to 1.2‐&mgr;m range, depending on minority carrier diffusion length and surface recombination velocity. The behavior of the Al‐Al2O3‐GaAs Schottky barrier junction yields an optimum open circuit voltage for an Al2O3thickness of about 15 A˚. The resistive loss study considered both the metal ohmic contact grid structure and the semiconductor resistivity. Conversion efficiencies as high as 6% are predicted for this structure with rather poor electrical properties of the GaAs films, i.e., &mgr;n=10 cm2/V sec, &mgr;p=1 cm2/V sec, and an infinite surface recombination velocity. Thus, if care is taken in the design and fabrication of a backwall MIS Schottky barrier solar cell, reasonable efficiencies can be achieved even if the semiconductor has poor electrical properties, as expected for a polycrystalline film.