Optimization of GaAs nanowire array for solar cells

The reflectance, transmittance and absorptance of GaAs nanowire (NW) arrays are calculated by solving Maxwell's equations using the finite element method. The model is compared with measurement results from well-ordered periodic GaAs NW arrays fabricated by dry etching. The model results are also compared with the reflectance measured from NWs grown by the Au-assisted vapor-liquid-solid (VLS) method. The optimum NW diameter, periodicity (spacing between NWs) and length are determined to maximize absorptance of the AM1.5G solar spectrum and short circuit current density in a NW array solar cell. The geometry structure of GaAs-Si two junction solar cell is also determined.