Plasma-etched, silicon nanowire, radial junction photovoltaic device

Abstract

A photovoltaic device based on radial p+n junction, plasma-etched silicon nanowires (SiNWs) is demonstrated. Cryogenic Si plasma etching after colloidal lithography is employed for the fabrication of ordered, high aspect ratio and perpendicular to the substrate nanowires. Radial junction is established by boron rapid thermal diffusion from spin-on dopants (SOD) solution. We study the effect of SOD annealing process conditions and show that shallow p+n junctions with depth of a few tens of nanometers and high dopant concentration are formed. Structural and electrical study of the final device is performed by current–voltage characterization under illumination, and compared to a planar Si photovoltaic device with similar p+n junction characteristics. Short-circuit current density of 12.3 mA cm−2, open-circuit voltage of 430 mV, fill factor of 0.64 and power conversion efficiency of 3.69% were obtained for the radial SiNW photovoltaic devices, significantly improved compared to the related figures for the corresponding planar device being 8.13 mA cm−2, 384 mV, 0.72 and 2.24%, respectively.