Photovoltaic semi-conductor devices

Abstract

Apparatus and method for constructing by means of standard high-yield microelectronic batch fabrication processes, reliable, monolithic high-voltage photovoltaic cells and highly efficient photovoltaic arrays therewith. A thin layer of single-crystalline semiconductor material containing a plurality of sublayers defining one or more active junctions in planes parallel to an upper irradiated surface thereof, overlies a supportive insulating substrate body. Widely spaced pairs of elongate heavily doped zones of opposite conductivity types produced by two short diffusion steps extend into the thin layer, defining photovoltaic cells therebetween and providing low-impedance conductive paths for photovoltaic carriers generated in the thin layer to the upper irradiated surface. By overlapping opposite-conductivity pairs of the heavily doped elongate zones, simultaneous dielectric isolation and series connection of adjacent cells is achieved. The elongate zones of individual cells can be interdigitated to decrease parasitic series resistance of the cells. A dielectric barrier interposed between adjacent cells can also be used to isolate the cells from one another. Means for creating an inversion layer at the irradiated surface, reflective means for causing multiple passes of received solar energy through the photovoltaic devices and use of an underlying junction formed by heavily and lightly doped regions of the same conductivity type can readily be employed to further increase cell efficiency.