The effects of trap-induced lifetime variations on the design and performance of high-efficiency GaAs solar cells

The authors investigate the impact of Shockley-Read-Hall (SRH) lifetime behavior directly on GaAs solar cell performance and design optimization for various lifetime-limiting defects, characterized by trap position, cross section, and trap density. It is demonstrated theoretically and experimentally, for a specific cell design, how far GaAs cell efficiency can be from the optimum efficiency if certain types of bulk defects limit the lifetime and are not properly accounted for. A realistic situation is considered where cell designers/manufacturers know the bulk lifetime at some nominal carrier concentrations but are unaware of the trap characteristics or defect responsible for this lifetime. An improved GaAs p/n heteroface cell design is proposed. This design utilizes a high-low junction and a thin base, with AlGaAs back-surface passivation