Wafer-Bonded Two-Terminal III-V//Si Triple-Junction Solar Cell with Power Conversion Efficiency of 36,1% at AM1.5G

In this work, we increased the power conversion efficiency of a wafer-bonded silicon-based triple-junction solar cell from 35.9 % to 36.1 % under the AM1.5g spectrum. This was achieved by implementing a rear-heterojunction cell concept into the middle cell. Besides, a more effective rear-side grating was designed for photo-current enhancement in the silicon bottom cell that increased the silicon subcell current by 1.6 mA/cm². The external radiative efficiency was quantified to be 1.5 times higher compared to a reference device with a GaInAsP homojunction middle cell. A luminescent coupling factor of 0.46 between the middle and bottom subcell was determined. The share of recombination in the space-charge region was experimentally shown to be insignificant as intended by the rear-heterojunction design. Overall, the open-circuit voltage increased by 60 mV compared to the previous generation. Given the established long-term stability of III-V and silicon based solar cells these results are promising steps towards the future employment of III-V/Si tandem solar cells.