Advanced photovoltaic concentrator cells. Final report, August 29, 1979-March 31, 1982

The objective of this project is to demonstrate the technical feasibility of producing monolithic stacked multibandgap solar cells having 30% conversion efficiency at 30/sup 0/C and 25% conversion efficiency at 150/sup 0/C under 500 to 1000 SUNs AM2 illumination. The following tasks were undertaken: (1) growth and optimization of single junction AlGaAs cells having bandgaps of 1.6 eV and 1.7 eV and AlGaSb cells having bandgaps of 0.95 eV and 1.1 eV; (2) development of techniques for joining these optimized single junction cells; (3) characterization of performance of the individual subcells and their stacked combinations with regard to light and dark I-V and spectral response behavior over the operating temperature range of 30 to 200/sup 0/C and for illumination levels of 1 to 1000 SUNs AM2. All of the individual subcomponents and processes which together make up the final device were successfully demonstrated in the course of the program. Working prototype two-junction cells were fabricated and tested. The major specific accomplishments of this program are: (1) successful demonstration of an optically transparent intercell ohmic contact having optical, electrical and mechanical characteristics suitable for use in a concentrator (greater than or equal to 500 SUNs) multijunction solar cell; (2) successful development more » of a new laser process for bonding dissimilar semiconductors; (3) successful demonstration of an Al/sub 0/ /sub 2/Ga/sub 0/ /sub 8/As homojunction solar cell suitable for use as the low bandgap subcell in a two-junction stacked converter; (4) demonstration of a working monolithic two-junction stacked solar cell employing dissimilar, nonlattice matched III-V semiconductor systems (AlGaAs and AlGaSb). « less