Investigation of High Efficiency Monolithic Multibandgap Solar Cells
Final rept. 15 Nov 1990-15 Nov 1991,
WASHINGTON UNIV SEATTLE
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This program involved investigations of A1GaAsGaAs multijunction solar cells. Most of the low level effort was devoted to studies of the electronic properties of A1GaAs films. Finite diffusion lengths could only be obtained for A1xGa1-xAs films with the aluminum concentration in the range from 0 to 0.1. Photoresponse of A1A1GaAs Schottky barriers were anlayzed to measure minority carrier diffusion length L. Values of L for p-type A1GaAs with x0 were typically in the range of 0 to 0.5 micron. It is clear that much more effort must be made to reduce oxygen and water impurity levels in the WSU barrel-type reactor before improved A1GaA Schottky barriers is explained as being due to improper mixing of A1 and Ga precursors. Results are discussed for films grown with improved mixing which do not exhibit the apparent bandgap shift. Estimated performance for a two-cell, A1GaAsGaAs structure are given based on characteristics of A1.37Ga.63As cells fabricated from wafers obtained from Varian, and GaAs cells fabricated for epi wafers grown with the WSU reactor.
- Electrical and Electronic Equipment
- Electric Power Production and Distribution