Current matched GaAsP/SiGe tandem device on Si over 20% efficiency under indoor measurement

Lattice matched and current matched GaAsP/SiGe tandem solar cell on Si has the potential of 40% efficiency. This paper describes our design, fabrication and improvement of this tandem solar cell. This tandem device has achieved efficiencies of 20.6% and 20.2% under 1X and 2.2X, respectively. Current matching between top cell and bottom cell is realized by manipulating the bottom cell active area and lamp spectrum during JV measurements. Improving the optics and cell structure should lead to current matching in this tandem device and produce an efficiency over 25% and over 30% under 1X and 20X standard AM1.5G, respectively.