Current matched three-terminal dual junction GaAsP/SiGe tandem solar cell on Si

•An improved SiGe bottom cell is integrated in the tandem device.•Three-terminal solar cell devices are fabricated and characterized.•Current matching is realized and analysed.•We report a corrected three-terminal tandem efficiency of 20.6%.

Lattice matched and current matched GaAsP/SiGe tandem solar cells on Si have the potential of 40% conversion efficiency [8]. A corrected three-terminal tandem efficiency of 20.6% under 1× illumination has been achieved, a relative improvement of approximately 9% compared to the 18.9% efficiency reported previously. Current matching is realized under 2.1× illumination. This is achieved by improving the bottom cell structure, manipulating the bottom cell active area and adjusting the light spectrum during light IV measurements. This paper describes the design of the improved structure, a simplified fabrication process and a detailed current matching analysis of this tandem solar cell. Pathways to achieve the realistic efficiency of over 25% under 1× illumination and near 30% under 20× illumination are also discussed.