High-efficiency radiation-resistant InGaP/GaAs tandem solar cells

Abstract

A world-record efficiency of 26.9% (AMO, 28/spl deg/C) has been obtained for InGaP/GaAs tandem solar cells fabricated by the MOCVD method. The radiation resistance of the InGaP/GaAs tandem solar cells has also been evaluated following 1 MeV electron irradiation. Degradation in tandem cell performance has been confirmed to be mainly attributed to large degradation in the GaAs bottom cell, which features a highly doped base layer. Similar radiation-resistance with GaAs-on-Ge cells has been observed for the InGaP/GaAs tandem cell. However, some recovery of the tandem cell performance has been found due to minority-carrier injection under light illumination or forward bias, which causes defect annealing in InGaP cells. The optimal design of the InGaP base layer thickness for current matching at end of life (EOL) (after irradiation with 10/sup 15/ electrons cm/sup -2/) has been examined.