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


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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Figure 1: Microscopy and spectroscopy of black silicon photoanodes.
Figure 2: PEC water oxidation performance of planar silicon and black silicon-based photoanodes.
Figure 3: Sulfite oxidation and charge separation properties of black silicon-based photoanodes.
Figure 4: Stability evaluation of black silicon-based photoanodes under in-air and in-electrolyte conditions.


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Work on ALD-based growth and structure characterization is supported by US Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), under Award # DE-SC0008711. The rest of the work is supported by the National Major Research Program of China (No. 2013CB932602); the Program of Introducing Talents of Discipline to Universities (B14003); National Natural Science Foundation of China (No. 51527802, 51232001, 51602020 and 51672026); and Beijing Municipal Science & Technology Commission.

Author information

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.

Correspondence to Yue Zhang or Xudong Wang.

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Yu, Y., Zhang, Z., Yin, X. et al. Enhanced photoelectrochemical efficiency and stability using a conformal TiO2 film on a black silicon photoanode. Nat Energy 2, 17045 (2017). https://doi.org/10.1038/nenergy.2017.45

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