Towards Perovskite Silicon Tandem Solar Cells with Optimized Optical Properties

Here we present an initial demonstration of a dual junction step-cell using single junction (SJ) GaAs
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cell, grown on Si
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Ge
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/Si substrates, as the top cell and Si as the bottom cell. To demonstrate step-cell, two SJ cells are connected in series, without removing SiGe/Si carrier from III-V cell, and illuminated Si cell area is varied. Measured efficiency of optimized demo step-cell under 1 sun and without anti-reflective coating on III-V cell is ~11.8% Using SJ cells characterization and optical data, we estimate maximum efficiency of bonded 1- μm GaAs
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// 650-μm Si step-cell to be ~26% at optimized total-to-top cell area ratio equal to 1.1. Results presented here show that step-cell can be used as added optimization design parameter for tandem cells.