Advanced photovoltaic concentrator cells. Annual report, August 28, 1979-August 28, 1980

The first year activities are described for a project aimed at demonstrating the technical feasibility of advanced high efficiency concentrator solar converters. The goal of the program is to achieve 30% conversion efficiency with a converter operating at 30/sup 0/C under 500 to 1000 SUNs AM1 illumination and 25% conversion efficiency with a converter operating at 150/sup 0/C under 500 to 1000 SUNs AM2 illumination. The approach is to fabricate two cell, non-lattice matched, monolithic stacked converters using optimum pairs of cells having bandgaps in the range of 1.6 to 1.7 eV and 0.95 to 1.1 eV. The high bandgap subcells are to be fabricated using MO-CVD or LPE to produce the needed AlGaAs layers of optimized composition, thickness and doping to produce high performance, heteroface homojunction devices. The low band-gap subcells are to be similarly fabricated from AlGa(As)Sb compositions by LPE. These subcells are then to be joined into a monolithic structure by an appropriate mechanical bonding technique which will also form the needed transparent intercell ohmic contact (IOC) between the two subcells. The major areas of activity are device modeling, materials development, and device fabrication and characterization. The accomplishments as well as the detailed approaches and results of these major areas have been described and discussed.