Efficiency calculations for AlxGa1-xAs-GaAs heteroface solar cells

A computer-assisted analysis of the Al
x
Ga
1-x
As-GaAs heteroface solar cell is done to find the dependence of cell efficiency on substrate doping level. Assumptions for carrier lifetime needed for the evaluation of efficiency are based on measurements of experimertal Al
x
Ga
1-x
As-GaAs heteroface cells. The results show the doping range 10
¹⁶
to 10
¹⁷
cm
^-3
to be the best for heteroface solar cells, because experimental evidence suggests that the lifetimes required for high-efficiency cells are difficult to obtain at very low and very high doping levels. Calculations based on a T
^3/2
temperature dependence for lifetimes agree well with early experimental efficiency versus temperature measurements on GaAs cells, but do not explain the results for an Al
x
Ga
1-x
As-GaAs heteroface cell reported by Hovel (1975).