Annealing Model for Lithium-Doped Solar Cells

A study has been performed on P/N lithium doped silicon solar cells to develop a mathematical model for the annealing of radiation damage. Experiments with low energy protons (0.25, 1.0, and 2.0 MeV) indicate that the annealing rates of proton damage are a function of the local position of damage within the solar cell base. Compton electron studies were used to determine introduction rates for annealable and unanneable damage. Pulsed 10 MeV electron tests permitted the observation of short circuit current recovery from 1 to 105 seconds for comparison with the mathematical model. These data are used as inputs into a diffusion limited reaction model of the defect annealing phenomena. Nonuniformities of the dopant profiles within the solar cell base are accounted for by a two-region model of the solar cell base. The two-region model of the solar cell using the diffusion limited reaction theory of annealing yields equations which describe the short circuit current recovery in lithium doped solar cells very well for both electron and proton damage.