Improvement of radiation resistance of multijunction solar cells by application of Bragg reflectors

Feasibilities to increase the radiation resistance of multijunction solar cells in using Bragg reflectors have been shown, and also the solar cell structure optimum parameters and the optical reflector design have been chosen. Spectral characteristics and photocurrent values of single- and multi-junction SCs with and without Bragg reflectors at different Ga(In)As subcell thicknesses have been simulated. The dependencies of the solar cell photocurrent on the minority charge carrier diffusion length in the Ga(In)As subcell base at different subcell thicknesses have been investigated for structures both with and without Bragg reflectors. A good fit of the calculated dependencies to the experimental ones have been obtained. Two designs of Bragg reflectors for multijunction solar cells have been proposed, which allow ensuring in the Ga(In)As subcell base an effective collection of minority charge carriers at the decrease of their diffusion length caused by radiation treatment.