Abstract :
A mathematical model has been developed which predicts the annealing kinetics of electron, proton, and neutron damage in lithium-doped silicon solar cells. The model to be presented uses the diffusion-limited reaction theory modified to account for excess lithium consumption and varying defect capture radius. Experimental data from short term radiations with 1 and 10 MeV electrons, 0.25, 1.0, and 2.0 MeV protons, and reactor neutrons are shown for comparison with calculated annealing curves. Data from a 24-month real time test in a simulated space environment of vacuum, Compton electrons, 100 keV protons, and UV radiation are also presented to illustrate the success of the model in predicting long term effects in cells where simultaneous damage introduction and annealing is occurring. These data are particularly interesting because they indicate that 1) the annealing of electron and proton damage is similar and apparently involves the same lithium-defect interactions, 2) that the annealing of neutron damage, while its annealing kinetics are similar and can be described by the same mathematical model as electron and proton damage, involves different defect-lithium interactions and the neutron annealing appears to be independent of prior cell histories in electron and proton environments, and 3) irradiations in combined environments of electrons and low-energy protons produce synergistic effects that are not predicted by any current damage models in both conventional cells and lithium doped cells.
