Hybrid functional calculated optical and electronic structures of thin anatase TiO2 nanowires with organic dye adsorbates

• Published in: Applied surface science 2015-11, Vol.354, p.437-442
• Main Authors: Ünal, Hatice, Gunceler, Deniz, Gülseren, Oğuz, Ellialtıoğlu, Şinasi, Mete, Ersen
• Format: Article
• Language: English
• Subjects: Anatase; Coumarin; Density; Dyes; Energy gaps (solid state); Mathematical analysis; Nanowires; Titanium dioxide
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2015.04.086

•Size effect on the band gap features of thin anatase (001) and (101) nanowires calculated at the screened Coulomb hybrid DFT approach.•HSE-optimized structures of coumarin and donor-pi-acceptor type C2-1 dye adsorbates on anatase (001) and (101) nanowires.•HSE charge density distributions of frontier states of dye-nanowire systems.•HSE+PCM calculations for C2-1 and coumarin on anatase nanowires including nonlinear solvation environment effects.•Optical properties of dye+nanowire combined systems. The electronic and optical properties of thin anatase TiO2 (101) and (001) nanowires have been investigated using the screened Coulomb hybrid density functional calculations. For the bare nanowires with sub-nanometer diameters, the calculated band gaps are larger relative to the bulk values due to size effects. The role of organic light harvesting sensitizers on the absorption characteristics of the anatase nanowires has been examined using the hybrid density functional method incorporating partial exact exchange with range separation. For the lowest lying excitations, directional charge redistribution of tetrahydroquinoline (C2-1) dye shows a remarkably different profile in comparison to a simple molecule which is chosen as the coumarin skeleton. The binding modes and the adsorption energies of C2-1 dye and coumarin core on the anatase nanowires have been studied including non-linear solvation effetcs. The calculated optical and electronic properties of the nanowires with these two different types of sensitizers have been interpreted in terms of their electron–hole generation, charge carrier injection and recombination characteristics.