Optical absorption in vertical silicon nanowires for solar cell applications

Photovoltaic research has moved from popular solar cells, based on crystalline silicon substrates with thicknesses of around 250 mu m, to the thin film structures saving large amount of the active material. The next generation of solar cells requires substantial increase of the energy conversion efficiency, which can be achieved by enhancing of the optical trapping inside the cell. In this work we study the efficiency of light trapping inside vertical silicon nanowire solar cells. The main focus is on the optical trapping inside single vertical nanowires, which can enhance optical absorption far beyond capabilities of a thin film. Spectral optical absorption modeling based on RCWA together with the electromagnetic field distribution analysis gave insight into the light trapping inside the nanowires. Results provide a guide for the optimization of nanowires diameters, density and length for maximal short circuit currents with minimal material demands.