Advanced photovoltaic concentrator cells. Quarterly technical progress report No. 3, March 1-May 31, 1980

Activities on a project aimed at demonstrating the technical feasibility of advanced high efficiency concentrator solar converters are reported. The goal of the program is to achieve 30% conversion efficiency with a converter operating at 30/sup 0/C under 500-1000 SUNs AM2 illumination and 25% conversion efficiency with a converter operating at 150/sup 0/C under 500-1000 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 bandgap subcells are to be similarly fabricated from AlGaSb(As) compositions by LPE. These subcells are then to be joined into a monolithic structure by an appropriate thermal bonding technique which will also form the needed transparent intercell ohmic contact (IOC) between the two subcells. The low bandgap subcell development activities have continued during this quarter. In addition, a problem of poor blue response observed for AlGaAs high bandgap cells grown by MO-CVD has been addressed and solved. The Nd-glass pulsed laser for bonding has been received and is being made operational.