Enhanced light absorption in perpendicular elliptical silicon nanocone array for solar cells.

Silicon nanowire-based arrays have demonstrated superior light trapping properties and great potential for next-generation photovoltaics. In this paper, we propose a perpendicular elliptical nanocone (PENC) array solar cell, which introduces an asymmetry in the direction parallel to the array surface in addition to the asymmetry in the direction normal to the array surface, which has been implemented in the circular nanocone (CNC) array. The PENC array displays more and higher resonant absorption peaks in the long wavelength compared with the CNC array. The newly exhibiting absorption peaks are found to be derived from periodical Bloch modes by the band-folding of the PENC array and cavity modes introduced by the asymmetry of the elliptical nanocone. The ultimate efficiency of the optimal PENC array is 24.3%, which is 17.4% higher than that of the optimal CNC one with the same nanocone height and 59.1% higher than that of the flat counterpart coated with a 70 nm zinc-oxide antireflection film. When the nanocone height is between 0.3 and 5.0 μm and the incident angle is between 0° and 80°, the PENC array demonstrates better light trapping property compared with the CNC ones.