Abstract: The specification describes a compound semiconductor solar cell and fabrication process therefor wherein both the P and N-type layers of the cell are polycrystalline semiconducting material and have large crystallites with grain boundaries of similar dimensions and spacings. These grain boundaries are spaced apart by a distance substantially greater than the optical absorption length, .LAMBDA., in one of the layers and by an amount sufficient to permit substantial numbers of photon-generated carriers in that one layer to cross the PN junction between the layers. Thus, substantial power is generated without the requirement for using expensive monocrystalline semiconductive materials.

Abstract: A thin film solar cell having adjacent layers of P and N type polycrystalline semiconductor material which define a PN junction boundary, the improvement comprising a layer of n-type polycrystalline cadmium sulfide disposed on a chosen substrate material and having large grains with lateral grain boundaries on the order of about 20 micrometers or greater and a layer of polycrystalline P-type indium phosphide disposed on said layer of polycrystalline cadmium sulfide and having a thickness on the order of between 1.0 and 4.0 micrometers and further having large replicated grain boundaries with lateral dimensions and spacings approximately the same as the lateral dimensions and spacings of said large grains of cadmium sulfide, whereby the lateral grain dimensions in said cadmium sulfide and indium phosphide layers are maximized while the quantity of indium in said solar cell is minimized.