Nanopinhole Passivating Contact Si Solar Cells Fabricated with Metal-Assisted Chemical Etching

摘要

Monocrystalline Si (c-Si) solar cells with passivating contacts based on dopedpolycrystalline Si (poly-Si) on ≈2.0 nm silicon oxide (SiO_x) require >1000 °Cthermal processing to create conducting pinholes in the SiO_x layer. However,this high thermal budget can induce bulk defects in the Czochralskic-Si wafers used as the cell absorber layer. In this work, it is demonstratedthat pinholes can instead be created using metal-assisted chemical etchingon planar or textured morphologies, at room temperature. This wet processcreates up to 200 nm wide conducting pinholes that are directly observedwith transmission electron and atomic force microscopies. High-performancehole-selective poly-Si/SiNy/SiO_x and electron-selective poly-Si/SiO_x passivatingcontacts are fabricated and implemented in laboratory-scale solar cells.This process development significantly broadens the range of passivationlayer materials, their thicknesses, and surface morphologies, which enablesthe design of poly-Si contacts with superior passivating quality.