Light trapping in large-scale photonic nanostructures fabricated from vertically aligned Ge quantum dots on crystalline silicon

To realize enhanced optical absorption in near-infrared region in crystalline Si (c-Si) solar cells, we investigated the light trapping in photonic nanostructures fabricated on c-Si substrate by using a wet etching technique with vertically aligned Ge quantum dots (QDs). From photoluminescence excitation measurements, we found that photocarrier generation is enhanced by more than two times in the sample with photonic nanostructures with respect to the reference sample without photonic nanostructures. The enhancement is explained well by light trapping owing to the photonic nanostructures at the incident surface. The enhanced optical absorption in the near-infrared region would be benefit to thinner c-Si solar cells, which fits to a promising direction of c-Si solar cell development.