Article

Enhanced photoelectrochemical efficiency and stability using a conformal TiO2 film on a black silicon photoanode

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Abstract

Black silicon (b-Si) is a surface-nanostructured Si with extremely efficient light absorption capability and is therefore of interest for solar energy conversion. However, intense charge recombination and low electrochemical stability limit the use of b-Si in photoelectrochemical solar-fuel production. Here we report that a conformal, ultrathin, amorphous TiO2 film deposited by low-temperature atomic layer deposition (ALD) on top of b-Si can simultaneously address both of these issues. Combined with a Co(OH)2 thin film as the oxygen evolution catalyst, this b-Si/TiO2/Co(OH)2 heterostructured photoanode was able to produce a saturated photocurrent density of 32.3 mA cm−2 at an external potential of 1.48 V versus reversible reference electrode (RHE) in 1 M NaOH electrolyte. The enhanced photocurrent relative to planar Si and unprotected b-Si photoelectrodes was attributed to the enhanced charge separation efficiency as a result of the effective passivation of defective sites on the b-Si surface. The 8-nm ALD TiO2 layer extends the operational lifetime of b-Si from less than half an hour to four hours.

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Author information

Author notes

    • Yanhao Yu
    •  & Zheng Zhang

    These authors contributed equally to this work.

Affiliations

  1. Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA

    • Yanhao Yu
    • , Xin Yin
    •  & Xudong Wang
  2. Department of Materials Physics, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China

    • Zheng Zhang
    • , Qingliang Liao
    • , Zhuo Kang
    • , Xiaoqin Yan
    •  & Yue Zhang
  3. Materials Science Center, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA

    • Alexander Kvit
  4. Beijing Municipal Key Laboratory of Advanced Energy Materials and Technologies, University of Science and Technology Beijing, Beijing 100083, China

    • Yue Zhang

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Contributions

Y.Y., Y.Z. and X.W. conceived the ideas, designed the experiments and oversaw the entire project. Y.Y. and Z.Z. performed the device fabrication, electrochemical measurements and data analysis. Y.Y. Q.L., Z.K. and X.Yan conducted the SEM, XPS and XRD characterizations. Y.Y., X.Yin and A.K. carried out the TEM, STEM and EELS mappings. Y.Y., Z.Z., Y.Z. and X.W. wrote the manuscript. All authors discussed the experiments and commented on the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to Yue Zhang or Xudong Wang.

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