Effect of ALD-Al2O3 Passivated Silicon Quantum Dot Superlattices on p/i/n+ Solar Cells

The photovoltaic (PV) nature of the silicon (Si) quantum dot super lattice (QDSL) is studied with an atomic-layer-deposited aluminum oxide film (ALD-Al
₂
O
₃
) and a conventional sputtered-grown amorphous silicon carbide film (a-SiC). The QDSL structures act as an intermediate layer in a p/i/n
⁺
Si solar cell. The QDSL consists of 4-nm Si on 2-nm SiC nanodisks (NDs) arrayed in an ALD-Al
₂
O
₃
and a-SiC passivation matrix. Formation of Si-NDs was confirmed by bright field scanning transmission electron microscope. A significant PV response in generating a high photocurrent density J
_sc
of 30.15 mA/cm
²
, open circuit voltage V
_oc
of 0.50 V, fill factor FF of 0.61, and efficiency η of 9.12% was observed in ALD-Al
₂
O
₃
/QDSL solar cell with respect to a-SiC/QDSL solar cell with J
_sc
of 26.94 mA/cm
²
, V
_oc
of 0.50 V, FF of 0.47, and η of 6.42%. A wide range of photo-carrier transports by the ALD-Al
₂
O
₃
/QDSL structure is possible in the external quantum efficiency spectra with respect to a-SiC/QDSL solar cell. The enhanced PV performance of the QD solar cells was clarified in terms of simulating the absorption contributions for all possible transitions in the nanostructure with different passivation films.