Simulation of Rough Silicon Nanowire Array for Use in Spin-on-Doped PN Core-Shell Solar Cells

In this paper we use the 3D TCAD Sentaurus workbench from Synopsis to simulate the photovoltaic performance of Silicon Nanowire Arrays (SINWAs) with a rough surface, as fabricated by metal assisted chemical etching and a core-shell pn junction, as obtained via spin-on-doping (SOD) diffusion. The roughness is imposed by a Gaussian autocorrelation function while the Sentaurus process tool simulates the doping profile as a function of diffusion time, temperature and initial SOD concentration. The finite-difference time-domain (FDTD) method is used to simulate both electrical and optical characteristics. The results show that the highest carrier generation occurs in the core and thus the depth of the junction should be strictly controlled by sub 900°C doping diffusion with high doping concentration in the SOD. The roughness of the wires reduces the reflectivity of a 2 μm long NWA to less than 2%. Using optimised junction depth and rough NWAs shows that the core-shell pn junction within the wire increases the efficiency by approximately 2%.