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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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.
The authors declare no competing financial interests.
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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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