Development of Novel Silicon Nanowire Array Solar Cells

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Silicon nanowires (Si NWs) with a diameter of 30 nm were fabricated by Metal-Assisted Chemical Etching with Silica nanoparticles (MACES) on crystalline silicon substrates. The optical measurements revealed the diameter of Si NWs was about 30nm and the diamond structure was maintained after the NW fabrication process. For the passivation of Si NWs, we have developed an atomic layer deposition (ALD) technique of aluminum oxide (Al2O3), and it was found that the effective minority carrier lifetime of Si NW arrays was drastically improved up to 100usec after annealing. Finally, we fabricated Si NW solar cells with a length of 7um on Si substrates. In the case of the solar cell without an Al2O3 layer, the efficiency was about 0.06%. However the efficiency of 1.2% (Voc: 0.40V, Jsc: 10mA/cm2, FF: 0.29) was successfully achieved by applying an Al2O3 layer, showing the importance of the Al2O3 passivation layer.