Theoretical analysis of an intermediate band in Sn-doped hematite with wide-spectrum solar response
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ORIGINAL PAPER
Theoretical analysis of an intermediate band in Sn-doped hematite with wide-spectrum solar response Wilayat Khan 1 & Jan Minar 2 & Saleem A. Khan 2 & Haroon Asghar 3 Received: 8 April 2020 / Revised: 15 October 2020 / Accepted: 20 October 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Hematite α-Fe2O3 is exposed to be an efficient photocatalytic material for the photoelectrochemical water splitting process under visible light. In the present work, we have improved the photocatalytic activity of hematite by varying tin concentration substituted for Fe in pristine hematite. To investigate the influence of the contents of Sn on the photocatalytic activity, various key properties like electronic structure and optoelectronic properties were studied based on density functional theory using generalized gradient approximation plus on-site Hubbard interaction within the WIEN2k computer program. The results of the electronic band structure show the insulating character of the pristine hematite exhibits a bandgap of 2.17 eV equals to Exp. one. The electronic structure calculations of the Sn-doped hematite explore the engineering of the orbitals around the Fermi level and result in a reduction in the bandgap, which is attributed to the corresponding Sn contents. The doping of Sn in Fe2O3 would introduce sub-bands (intermediate band) in between the valence band maximum (VBM) and Fermi level EF, and more interestingly, half-filled intermediate bands appear around the Fermi level with the increase of Sn contents. To see the effect of intermediate bands on the optoelectronic features of the Sn-doped hematite, we also calculated the optical properties of pristine and doped hematite, which predict extra peaks assigned to transitions of electrons from intermediate bands in the infrared region. Our findings explore that the presence of intermediate bands facilitates the PEC activity of water splitting of Fe2O3, shifting from visible light to infrared region. Here, we demonstrate the idea of intermediate bands in hematite for distinctive device applications. Keywords Photocatalytic materials . Electronic structure . Intermediate band . Linear optical properties . DFT . Energy conversion
Introduction Photoelectrochemical (PEC) water splitting, i.e., 2H2O → 2H2 + O2, provides an effective pathway for light energy conversion and thus has a great impact on the worldwide energy crises and environment [1]. To explore the use of PEC, a stable, nontoxic, and low-cost semiconductor is acquired. The semiconductor must absorb the solar light to produce
* Wilayat Khan [email protected] 1
Department of Physics, Bacha Khan University, Charsadda, KP, Pakistan
2
New Technologies - Research Centre, University of West Bohemia, Univerzitni 8, 306 14 Pilsen, Czech Republic
3
National Center for Physics, Quaid-i-Azam University Campus, Islamabad 45320, Pakistan
the electron-hole pair and transport these charge carriers towards the liquid/solid interfaces at the photoanode and reduction takes place at t
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