Modelling low energy proton radiation effects on solar cells

Past work has shown that the degradation of gallium arsenide solar cells in space radiation environments can be described with a single curve for a wide range of incident particle energies using the displacement damage dose (D/sub d/) approach. This greatly simplifies the prediction of the performance of GaAs solar cells exposed to complex particle spectra. A similar approach has not been applied to silicon solar cells because the large diffusion length in silicon means that protons of relatively high energy lose a significant fraction of their energy in the active region of the cell. The proton energy is, therefore, not well defined in the device. In this paper we show how the Monte Carlo code SRIM can be used to extend the D/sub d/ approach to cases where this occurs. The analysis will be applied to both single junction Si and GaAs solar cells. Space prediction comparisons will also be made using both the experimentally-derived (JPL) and simulation-derived (SRIM) relative damage coefficients (RDCs) for maximum power (P/sub max/) in Si solar cells.