Polycrystalline p-type films were vacuum deposited onto TiB/sub 2/ coated alumina and sapphire substrates. Epitaxial layers were also formed on single crystal silicon substrates. Junctions in the layers were created by both gaseous diffusion in a tube furnace and by vacuum deposition. The TiB/sub 2/ vacuum deposited bottom electrodes have resistivities between 30 and 40 ..mu.. ..cap omega..-cm. All-vacuum-deposited solar cells were fabricated for the first time. Efficiencies approaching those in the diffused junction devices were achieved. The n-layers were deposited on the previously deposited p-layer/TiB/sub 2//ceramic sandwiches by vacuum deposition of silicon in a phosphine (PH/sub 3/) atmosphere. Photovoltaic data in diffused junction samples, including efficiency and spectral response measurements, indicate that crystallite size may no longer be the limiting factor in achieving high efficiency; rather, performance is now being limited by the presence of impurities in the vacuum deposition silicon base region.

This report is one of a series of studies that have been made by the Applied Physics Laboratory, or its subcontractors, to examine the technical and economic feasibility of the utilization of geothermal energy at the request of potential users.