Comparative radiation resistance, temperature dependence and performance of diffused junction indium phosphide solar cells

Abstract

A comparison was made between indium phosphide solar cells whose p-n junctions were processed by the open tube capped diffusion and closed tube uncapped diffusion of sulfur into Czochralski-grown p-type substrates. Air mass zero total area efficiencies ranged from 10% to 14.2%, the latter value being attributed to cells processed by capped diffusion. The radiation resistance of the latter cells was slightly better under 1 MeV electron irradiation. However rather than being process dependent, the difference in radiation resistance could be attributed to the effects of increased base dopant concentration. In agreement with previous results, both cells exhibited radiation resistance superior to that of gallium arsenide cells. The lowest temperature dependence of the maximum power dP m / dT was exhibited by cells prepared by open tube capped diffusion. The average value of dP m / dT , including cells of both types, was found to be — ( 5.3 ± 1.2) × 10 −2 mW cm −2 K −1 at 60 °C. Calculated values of dV oc / dT were in reasonable agreement with experimental values. However, contrary to previous results, no correlation was found between the open-circuit voltage V oc and the temperature dependence of P m . It was concluded that additional process optimization was necessary before concluding that one process was superior to the other.