Photovoltaic performance improvement of GaAs1-xBix nanowire solar cells in terms of light trapping capability and efficiency

Abstract

This paper investigates optoelectronic performance of nanowire (NW) solar cells using GaAs and its alloy GaAs1-xBix for three different mole fractions of Bi e.g., x = 0.01, 0.043, 0.078 using extensive numerical simulation in order to evaluate the potential of the alloy as a solar cell material. Finite-difference time-domain (FDTD) method is used to obtain the optimum geometric dimensions of the nanowire in order to achieve maximum photocurrent. GaAs0.922Bi0.078 NW solar cell of length 2-µm and optimized diameter D = 140 nm with filling ratio (FR) of 0.5, produces a maximum Jsc of 49.31 mA/cm2 which is 23% higher than its GaAs counterpart. Additionally, GaAsBi NW exhibits much higher absorption, and lower reflection as well as transmission coefficients for the incident optical irradiation, due largely to its bandgap bowing property owing to incorporation of Bi, as compared to GaAs NW. Furthermore, we present electric field distribution and optical generation rate profiles under the incident irradiation in NWs to obtain a better insight into the device physics. Various material and transport parameters of the novel alloy material required to carry out electrical simulation using Lumerical 3D charge transport simulator, are presented in detail, and the effect of SRH recombination lifetime on the electrical performance i. e., open circuit voltage Voc and power conversion efficiency (PCE) of the NW solar cells is studied. Our findings reveal that GaAs0.99Bi0.01 NW exhibits the maximum PCE of 34.34% found to be 6.425% larger than that of GaAs NW under AM 1.5G illumination.