The metal–thin‐insulator–semiconductor structure recently has been shown to have potential as a simple efficient solar cell. A general theory of these solar cells as well as experimental results for silicon devices optimized on the basis of this theory are described. The experimental devices have exceptionally good open‐circuit voltages. Under illumination resulting in a short‐circuit current density of 32 mA/cm2, an open‐circuit voltage of 618 mV and a fill factor of 0.6 were obtained.