Vertically arrayed Si nanowire/nanorod-based core-shell p-n junction solar cells

Vertically arrayed Si nanowire/nanorod-based core-shell p-n junction solar cells have been fabricated by a solid-state phosphorus diffusion to convert the shell of the boron-doped p-type Si nanowires to n-type, thus forming a core-shell p-n junction structure. The nanowires with a nanosphere defined diameter were fabricated by an Au-film assisted electrochemical etching method, enabling controlled junction formation. The Si nanowire arrays show superior optical properties over a wide range of spectrum. In addition, longer nanowires are more effective for light trapping and absorption which is more advantageous for efficient energy harvesting. The cells show a high energy conversion efficiency of 1.47%, a significant improvement from the previously reported Si nanowire-based core-shell junction solar cells where the core-shell junctions were formed by an oppositely doped Si deposition on preformed Si nanowires. The relatively high efficiency might be mainly attributed to the extremely low reflectivity of the nanowire arrays for efficient energy harvesting and a pristine junction formation by the diffusion method. (C) 2010 American Institute of Physics. [doi:10.1063/1.3520217]