Density Functional Study of the Interfacial Electron Transfer Pathway for Monolayer-Adsorbed InN on the TiO₂ Anatase (101) Surface

Abstract

Density functional theory (DFT) in connection with ultrasoft pseudopotential (USP) and generalized gradient spin-polarized approximations (GGSA) is applied to calculate the adsorption energies and structures of monolayer-adsorbed InN on the TiO(2) anatase (101) surface and the corresponding electronic properties, that is, partial density of states (PDOS) for surface and bulk layers of the TiO(2) anatase (101) surface and monolayer-adsorbed InN, to shed light on the possible structural modes for initial photoexcitation within the UV/vis adsorption region followed by fast electron injection through the InN/TiO(2) interface for an InN/TiO(2)-based solar cell design. Our calculated adsorption energies found that the two most probable stable structural modes of monolayer-adsorbed InN on the TiO(2) anatase (101) surface are (1) an end-on structure with an adsorption energy of 2.52 eV through N binding to surface 2-fold coordinated O (O(cn2)), that is, InN-O(cn2), and (2) a side-on structure with an adsorption energy of 3.05 eV through both N binding to surface 5-fold coordinated Ti (Ti(cn5)) and In bridging two surface O(cn2), that is, (O(cn2))(2)-InN-Ti(cn5). Our calculated band gaps for both InN-O(cn2) and (O(cn2))2-InN-Ti(cn5) (including a 1.0-eV correction using a scissor operator) of monolayer-adsorbed InN on the TiO(2) anatase (101) surface are red-shifted to 1.7 eV (730 nm) and 2.3 eV (540 nm), respectively, which are within the UV/vis adsorption region similar to Gratzel's black dye solar cell. Our analyses of calculated PDOS for both surface and bulk layers of the TiO(2) anatase (101) surface and monolayer-adsorbed InN on the TiO(2) anatase (101) surface suggest that the (O(cn2))(2)-InN-Ti(n5) configuration of monolayer-adsorbed InN on the TiO(2) anatase (101) surface would provide a more feasible structural mode for the electron injection through the InN/TiO(2) interface. This is due to the presence of both occupied and unoccupied electronic states for monolayer-adsorbed InN within the band gap TiO(2) anatase (101) surface, which will allow the photoexcitation within the UV/vis adsorption region to take place effectively, and subsequently the photoexcited electronic states will overlap with the unoccupied electronic states around the lowest conduction band of the TiO(2) anatase (101) surface, which will ensure the electron injection through the InN/TiO(2) interface. Finally, another thing worth our attention is our preliminary study of double-layer-adsorbed InN on the TiO(2) anatase (101) surface, that is, (O(cn2))(2)-(InN)(2)-Ti(cn5), with a calculated band gap red-shifted to 2.6 eV (477 nm) and a different overlap of electronic states between double-layer-adsorbed InN and the TiO(2) anatase (101) surface qualitatively indicated that there is an effect of the thickness of adsorbed InN on the TiO(2) anatase (101) surface on both photoexcitation and electron injection processes involved in the photoinduced interfacial electron transfer through InN/TiO(2). A more thorough and comprehensive study of different la...

DRIFTS Evidence for Facet-Dependent Adsorption of Gaseous Toluene on TiO2 with Relative Photocatalytic Properties

“…Similarly on the T101 surface (Figure b), the band at 3033 cm –1 corresponding to C–H stretching vibrations of the aromatic ring, the bands at 2929, 2917, 2909, 2853, and 2842 cm –1 corresponding to asymmetric and symmetric C–H stretching vibrations of the methyl group, and the band at 1436 cm –1 corresponding to methyl bending vibration also appear after introduction of toluene. It should be pointed out that the positions of these characteristic bands of adsorbed toluene on T101 are red-shifted slightly compared to that on T001, which may be attributed to the different Ti 4+ adsorption sites on {001} and {101} facets for toluene adsorption. , Notably, the adsorption takes much longer for T101 to reach a stable level. For easy understanding, the integrated areas of the characteristic bands of C–H stretching vibrations of toluene on T001 and T101 facets as a function of adsorption time are shown in Figure .…”

A density functional theory study of electronic properties of transition metals doped silicon carbide monolayer

“…The DOS indicated that states are basically absence of spin polarization but the states on fermi level are spin‐polarized to some extent. The contribution of iodide states near fermi level points to the feasibility of charge transfer from the host slab to the adsorbent [26].…”

Thin Film InN/Anatase Bilayers as a Substitute Dye/Semiconductor Interface for Solar Cells

“…Experimental [1] and theoretical [2] literature suggest that the light harvesting component of the anatase based dye-sensitized solar cell (DSSC), typically a Ru-based dye molecule, could be replaced by a monolayer of InN. In [1], a "monolayer" of InN was deposited via chemical vapor deposition on a nanoparticulate anatase TiO 2 substrate.…”

“…In [1], a "monolayer" of InN was deposited via chemical vapor deposition on a nanoparticulate anatase TiO 2 substrate. Calculations [2] indicate that electrons from InN would be excited over a 1.7 eV band gap into the conduction band, from whence the electrons would be injected from the InN conduction band into the TiO2 conduction band via band gap overlap. Calculations [2] indicate that electrons from InN would be excited over a 1.7 eV band gap into the conduction band, from whence the electrons would be injected from the InN conduction band into the TiO2 conduction band via band gap overlap.…”

“…X-ray diffraction of InN on TiO2 showing InN crystallinity.Optical band gap determination for the InN/TiO2 bilayer after annealing Plot of the square root of the optical absorption times the photon energy vs. photon energy for determining the optical band gap of the InN/TiO 2 bilayer after sintering to 400 ºC. Using a linear fit on the (α*E ph ) 1/2 vs. E ph curve, the sample optical band gap is determined to be 1.10 ± 0.02 eV, with the uncertainty coming from the curve fit (Figure 3).The sample of five alternating layers of InN and TiO 2 are red-brown in appearance, indicating that they are the partially amorphous, less conductive InN, which does not seem to be affected by deposition on top of TiO 2 .…”