Abstract
We report significant photoelectrochemical activity of Y-doped BiFeO3 (Y-BFO) epitaxial thin films deposited on Nb:SrTiO3 substrates. The Y-BFO photoanodes exhibit a strong dependence of the photocurrent values on the thickness of the films, and implicitly on the induced epitaxial strain. The peculiar crystalline structure of the Y-BFO thin films and the structural changes after the PEC experiments have been revealed by high resolution X-ray diffraction and transmission electron microscopy investigations. The crystalline coherence breaking due to the small ionic radius Y-addition was analyzed using Willliamson-Hall approach on the 2θ-ω scans of the symmetric (00 l) reflections and confirmed by high resolution TEM (HR-TEM) analysis. In the thinnest sample the lateral coherence length (L∥) is preserved on larger nanoregions/nanodomains. For higher thickness values L∥ is decreasing while domains tilt angles (αtilt) is increasing. The photocurrent value obtained for the thinnest sample was as high as Jph = 0.72 mA/cm2, at 1.4 V(vs. RHE). The potentiostatic scans of the Y-BFO photoanodes show the stability of photoresponse, irrespective of the film’s thickness. There is no clear cathodic photocurrent observation for the Y-BFO thin films confirming the n-type semiconductor behavior of the Y-BFO photoelectrodes.
Highlights
The peculiar crystalline structure of the Y-doped BiFeO3 (Y-BFO) thin films and the structural changes after the PEC experiments have been revealed by high resolution X-ray diffraction and transmission electron microscopy investigations
The high photovoltages are due to the spontaneous polarization in ferroelectric materials which led to high built-in potential in the volume, the charge separation and drift being improved, in contrast with metal oxides
The Pulsed Laser Deposition (PLD) method has been employed for the deposition of 3% Y-BFO thin films with different thickness values, from 20 nm to 75 nm
Summary
The peculiar crystalline structure of the Y-BFO thin films and the structural changes after the PEC experiments have been revealed by high resolution X-ray diffraction and transmission electron microscopy investigations. Small band-gap inorganic or hybrid perovskite materials are considered, from this point of view, the step in clean energy production. Reports on the photovoltaic properties of epitaxial BFO thin films deposited on DyScO3 substrate using a step-flow method for achieving layer-by-layer growth mode, pointing out the above band gap generated photovoltages, have shown the potential of this material in harvesting solar energy[7]. They showed that the ferroelectric domain structure can induce a variation up to 8,000% in the photocurrent and 0.330 V shift in the onset potential, implying the use of domain engineering in ferroelectric materials for effective charge separation and collection, for efficient water splitting photoanodes
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