Effect of MACE Parameters on Electrical and Optical Properties of ALD Passivated Black Silicon

Kexun Chen, Toni Pasanen, Ville Vähänissi, Hele Savin

Research output: Contribution to journalArticleScientificpeer-review

24 Citations (Scopus)
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Metal-assisted chemical etching (MACE) enables efficient texturing of diamond-wire sawn multicrystalline silicon (mc-Si) wafers. However, the excellent optics are often sacrificed by polishing the surface to achieve better surface passivation with chemical-vapor-deposited (CVD) silicon nitride (SiNx). In this
work, we show that a polishing step is not required when CVD SiNx is replaced with atomic-layer-deposited (ALD) aluminum oxide (Al2O3). Indeed, while polishing increases reflectance, it has in general only very modest effect on surface recombination velocity of ALD-passivated b-Si. Furthermore, since ALD Al2O3 is compatible with various surface morphologies due to its excellent
conformality, the MACE parameters can be more freely adjusted. First, the concentration of silver nitrate (AgNO3) in AgNO3/H2O solution that is used to deposit Ag nanoparticles is shown to affect the final b-Si morphology. Instead of needle-shaped b-Si produced by 5 mmol/L AgNO3 concentration, two orders of magnitude lower AgNO3 concentration produces porous structures, which are more challenging to passivate. Additionally, we demonstrate that a separate Ag nanoparticle removal step in nitric acid (HNO3) is not a prerequisite for high carrier lifetime. Instead, Ag nanoparticles present during polishing in a HF/HNO3/H2O solution affect the final b-Si morphology by accelerating the etching of Si. The results demonstrate that no trade-offs are necessary between optical and electrical properties of MACE b-Si when using ALD.
Original languageEnglish
Article number8728144
Pages (from-to)974-979
Number of pages6
JournalIEEE Journal of Photovoltaics
Issue number4
Early online date2019
Publication statusPublished - 1 Jul 2019
MoE publication typeA1 Journal article-refereed


  • black silicon
  • nanostructure
  • metal assisted chemical etching
  • atomic layer deposition


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