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

• Published in: Advanced energy materials 2018-11, Vol.8 (33), p.n/a
• Main Authors: Ro, Yun Goo, Chen, Renjie, Liu, Ren, Li, Nan, Williamson, Theodore, Yoo, Jinkyoung, Sim, Sangwan, Prasankumar, Rohit P., Dayeh, Shadi A.
• Format: Article
• Language: English
• Subjects: Carrier recombination; Circuits; Collection; Design optimization; Energy conversion efficiency; Material Science; microwire facet; Passivity; Photovoltaic cells; Silicon dioxide; Silicon nitride; solar cell; Solar cells; SOLAR ENERGY; surface passivation; surface recombination; Trapping; Wavelengths
• ISSN: 1614-6832; 1614-6840
• DOI: 10.1002/aenm.201802154

Surface 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. Parametric studies of the influence of surface facet crystal orientation, surface passivation, and array geometrical details on surface recombination and carrier collection in Si microwire solar cells with radial p‐n junctions are performed and their electrical and optical properties are analyzed. The results provide design guidelines in optimizing geometrical parameters for highly efficient microwire solar cells.