InAs quantum dots in a GaAs matrix are studied. Those quantum dots are used in applications to enhance the overall
efficiency of multi-junction solar cells beyond 40%. Photoluminescence measurements at 77 K using a 532 nm laser
have been performed on an epitaxially grown structure of self-assembled InAs quantum dots in a GaAs matrix upon a Ge
substrate, where three energy levels are determined at En=0=1.01 eV, En=1=1.07 eV and En=2=1.13 eV. Theoretical
calculations of the energy levels determine the quantum dots to be 7 nm high and have a 37 nm base diameter, which is
close to atomic force microscopy measurements performed on the samples. Intensity dependant photoluminescence
measurements reveal the saturation of the first excited energy level at 5×106 W/m2. A general model for the saturation of
the first quantum dot excited energy level is then developed. This saturation model is applied to the AM1.5D solar
spectrum at 297 K to determine the concentration of solar energy needed to saturate the first excited energy level within
a multi-junction solar cell. Saturation was determined to be at ~1.56×104 suns (where 1 sun = 1000 W/m2). Since current
solar concentrations are between 500-1000 suns concentration, the saturation of such quantum dots will not occur.
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