Strongly enhanced light trapping in a two-dimensional silicon nanowire random fractal array

An easy-to-fabricate ‘forest’ of silicon nanowires with a greatly enhanced ability to trap light has been developed by researchers in Italy. Materials that strongly trap light are highly desired for boosting the efficiency of solar cells. Barbara Fazio of the Institute for Chemical and Physical Processes in Messina and co-workers have made a two-dimensional array of silicon nanowires that efficiently traps light over the entire visible spectrum as well as into the near-infrared. They show that the random fractal arrangement of the nanowires causes light to bounce around many times within the array, thereby increasing the absorbance of light. The nanowire arrays can be readily fabricated by cheap, silicon-compatible processes. They also exhibited enhanced Raman scattering and photoluminescence, making them potentially useful for a new class of light-emitting devices.