Surface Passivation and Carrier Collection in {110}, {100} and Circular Si Microwire Solar Cells

Abstract

AbstractSurface recombination is a major bottleneck for realizing highly efficient micro/nanostructure solar cells. Here, parametric studies of the influence of Si microwire (SiMW) surface‐facet orientation (rectangular with flat‐facets, {110}, {100} and circular), with a fixed height of 10 µm, diameter (D = 1.5–9.5 µm), and sidewall spacing (S = 2.5–8.5 µm), and mesh‐grid density (1–16 mm−2) on recombination and carrier collection in SiMW solar cells with radial p‐n junctions are reported. An effective surface passivation layer composed of thin thermally grown silicon dioxide (SiO2) and silicon nitride (SiNx) layers is employed. For a fixed D of 1.5 µm, tight SiMW spacing results in improved short‐circuit current density (Jsc = 30.1 mA cm−2) and sparse arrays result in open‐circuit voltages (Voc = 0.552 V) that are similar to those of control Si planar cells. For a fixed S, smaller D results in better light trapping at shorter wavelengths and higher Jsc while larger D exhibits better light trapping at larger wavelengths and a higher Voc. With a mesh‐grid electrode the power conversion efficiency increases to 15.3%. These results provide insights on the recombination mechanisms in SiMW solar cells and provide general design principles for optimizing their performance.