The effect of dislocations on the performance of gallium arsenide solar cells

The dependence on dislocation density of GaAs solar cell performance is modeled. Reductions in short-circuit current are calculated with an effective diffusion length that is dependent on dislocation density. The electronic properties of the dislocations were examined to predict reductions in open-circuit voltage. The dislocations in n-type GaAs are modeled as inverted p-type regions based on the properties of GaAs grain boundaries and GaAs surfaces. These inverted regions form low-voltage diodes that act in parallel with the bulk GaAs diode and degrade open-circuit voltage. This approach predicts that GaAs solar cells on Si substrates with dislocation densities of 10⁶ cm^-2 can attain AM1.5 efficiencies of 20%.