Anomalous changes in the spectral response of solar cells which had been irradiated with high fluences of 1MeV electrons were modelled by using a device simulator. The spectra could be modelled satisfactorily by considering decreases in carrier concentration, minority-carrier diffusion length, and surface recombination velocity. Conduction-type conversion of the base layer had to be assumed in order to fit the spectral response after 1MeV electron irradiation to fluences greater than about 5 x 1016/cm2. This was experimentally confirmed by electron beam-induced current data. The changes could be explained by the generation of vacancies, and P diffusion from the emitter, due to electron irradiation. This led to compensation of the base layer and to an increase in junction depth.

Analysis of Structural Changes of Si Solar Cells Irradiated with High-Fluence Electrons M.Imaizumi, S.J.Taylor, M.Yamaguchi, T.Ito, T.Hisamatsu, S.Matsuda: Journal of Applied Physics, 1999, 85[3], 1916-20