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 atomiclayer-deposited aluminum oxide film (ALD-Al₂O₃) 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-Al₂O₃ 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 30.15mA/cm²open circuit voltage V_oc of 0.50 V, fill factor FF of 0.61, and efficiency η of 9.12% was observed in ALD-Al2O3/QDSL solar cell with respect to a-SiC/QDSL solar cell with J_sc of 26.94 mA/cm2, V_oc of 0.50 V, FF of 0.47, and ? of 6.42%. A wide range of photo-carrier transports by the ALD-Al2O3/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.