Design of GaAs nanowires array based photovoltaic solar cells: simulations of optical reflectance

Abstract

We report the optical response of a periodic square array of GaAs nanowires embedded in epoxy as a candidate for photovoltaic solar cells. The simulated system is a multilayer array constituted by alternating layers of epoxy and an effective medium constituted by GaAs nanowires arrays embedded in epoxy. To discuss the optical response, we investigate the reflectance dependence on the number of bilayers considered in the array and the angle of incident light. The GaAs nanowire dielectric function is described in terms of Webb formalism to take into account the confinement energy of the excitons. The effective dielectric function of GaAs nanowires embedded in epoxy is evaluated within the Maxwell–Garnett theory. We evaluate the reflectance for s- and p-polarized light through the transfer matrix formalism for bilayers. For both s- and p-polarization, we observe an oscillating behavior of the reflectance, similar to that reported in the literature. We have also obtained a feature peaked around 850 nm. While the oscillations can be ascribed to multiple interference from periodic bilayers, the peak at 850 nm can be understood in term of the gap energy in the nanowire dielectric function. Attending to the reflectance dependence on the light incidence angle, we have found that for s-polarized light, the reflectance is higher with increasing angles, in comparison to p-polarized light cases.