solar cells using surface-activated wafer bonding (SAB). We observe maximum power
conversion efficiency of 25.2% at 1-sun for a 3J device and 21.8% for a 2J device. The EQE
analysis of the cells was carried out, which suggested that the 3J device performance was
limited by the JSC generated at the Si subcell. We demonstrate that higher efficiencies are
feasible through design and adjustment of anti-reflective coating (ARC), GaAs bonding layer …