Efficiency Improvements in GaAs-on-Si Solar Cells

The thermal cycle growth (TCG) method is shown to be effective in improving GaAs/Si photovoltaic performance. Transmission electron microscope studies revealed that dislocation densities were reduced by approximately an order of magnitude and minority-carrier lifetimes increased by more than a factor of two. The efficiency of GaAs-on-Si cells were increased from 11.2% to 17.6% (one-sun) and from 13.9% to 18.5% (concentrated light) by use of the TCG technique. Improvements in basic GaAs cell growth and processing technology were also responsible for a portion of these increases, as GaAs/GaAs control cell efficiencies climbed from 21.3 to 24.3% over the span of these experiments.