Exploration of Lattice-matched Monolithic AlGaInP/AlGaAs/GaInAs/GaInNAs/Ge 5-junction Solar Cell Grown by MOVPE

A Ge-based lattice-matched monolithic AlGaInP/AlGaAs/GaInAs/GaInNAs/Ge 5-junction (5J) solar cell is fabricated for exploring commercial space cell with ultra-high efficiency towards 36%. Firstly, an AlGaInP/AlGaAs/GaInAs/Ge four-junction (4J) cell is obtained with a space efficiency of 30.11% (AM0, 1-sun). Finally, a 5J device with an active area of 11.75 cm
²
is achieved with a lower efficiency of 28.7% by inducing a 1.05 eV GaInNAs subcell into the 4J structure. The photovoltaic performance of 5J cell is restricted by GaInNAs subcell. While, the short-circuit current (J
_SC
) as 11.5 mA/cm
²
indicates that Ge-based 5J cell is a viable path to ultra-high efficiency space cell.