Investigation of High Efficiency Monolithic Multibandgap Solar Cells
Abstract
This program concerned investigations of multibandgap solar cell structures with potential efficiencies greater than 40%. The basic concept utilized a monolithic stack of three or more cells based on Aluminum Gallium Arsenide and Indium Gallium Arsenide ternary compounds. In particular, the planned work for the two-year program was to involve research related to a three-cell stack comprised of a top Al.37Ga.63As cell, a middle Gallium arsenide cell and a bottom In.3Ga.7As cell. Efforts first concentrated on GaAs cell growth and fabrication, and then on AlGaAs film growth. Although significant progress was made in the development of AlGaAs film growth, efforts to grow InGaAs films and solar cells were not initiated. GaAs solar cells were fabricated from epi-wafers grown at WSU Tri-Cities. The cells had a p/n structure with Gold metallization and silicon monoxide anti-reflection coatings. Cells exhibited AM1.5 efficiencies greater than 21%. Studies of AlGaAs included development of procedures for growth of films of known aluminum concentration and measurement of minority carrier properties. The minority carrier diffusion length was found to be 0.6 micrometers for AlGaAs with a composition corresponding to 10% aluminum. Films with larger amounts of Al exhibited much lower values of diffusion length. Studies were conducted which determined that oxygen impurity levels in the AlGaAs were degrading minority carrier properties.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 25, 1991
- Accession Number
- ADA238718
Entities
People
- Lawrence Olsen