Broadband Absorptance High Efficiency Silicon Nanowire Fractal Arrays for Photovoltaic Applications

Nanowire arrays have been proposed to enhance light trapping, increase efficiencies, and reduced material cost in photovoltaic solar cells. In this work we present a new crystalline silicon nanowire array structure, inspired by fractal geometry. The array structure is assumed to be an infinite 2D array in the x and y directions, and composed of vertically aligned SiNW suspended in air. Hexagonal fractal-like geometry is adapted in arranging cylindrical SiNW in these arrays. Full-wave finite element method 3D simulation is used to compute reflectance, transmittance and absorptance of the array for a normal incidence plane wave. The proposed fractal-like distribution of SiNW arrays yield broad absorption spectrum and enhanced efficiency while using less material. The efficiency of the proposed fractal-like SiNW arrays achieve ?100% enhancement over that of the equivalent thickness flat c-Si film, and ?18% enhancement over an equivalent height hexagonal array. The proposed optimized structures achieved a filling ratio ?25%, which is ?33% less than the corresponding hexagonal array.