TY - JOUR
T1 - Electronic properties of Nano-porous TiO2- and ZnO-Thin Films-comparison of simulations and experiments
AU - Wunderlich, Wilfried
AU - Oekermann, Torsten
AU - Miao, Lei
AU - Hue, Nguyen Thi
AU - Tanemura, Sakae
AU - Tanemura, Masaki
PY - 2004
Y1 - 2004
N2 - The electronic properties of anatase, rutile and ZnO thin films are of interest for many applications such as photocatalysis, or dye-sensitised solar cells. This paper describes the correlation between microstructure and electronic properties of photoactive TiO2 and ZnO thin films, which are based on experimental data and are interpreted by ab-initio simulations. This study considers the influence of three main factors on the optical and electrical properties: Strain of epitaxially grown thin films, nano-particle- and nano-pore- structures, and finally the interface to adsorbed dye molecules. The first part describes the search for a suitable substrate to grow titania layers with a smaller band-gap and ab-initio simulations showed excellent agreement to the experimental data. A narrow band gap is predicted for strained lattice constants in the a-direction and compressed in the c-direction. The second part describes the fabrication of nano-porous thin films by sol-gel processing using appropriate precursor solutions (titanium-tetra-iso-propanol (TTIP), di-ethanol-amine (DEA)) applied on suitable nano-templates. Due to the surface curvatures the nano-porous TiO2 has a narrow band gap, while nano-particles of titania show a larger band-gap. In the third part Dvxα ab-initio simulations were applied to dye-sensitized solar cells (DSSC), based on ZnO and TiO2. The results are compared to experimental data obtained for different dyes on nanoporous electrodeposited ZnO films. The ranking in efficiency found experimentally for the different combinations could be explained by the calculation results. This finding is discussed in the view of further optimization of solar cells.
AB - The electronic properties of anatase, rutile and ZnO thin films are of interest for many applications such as photocatalysis, or dye-sensitised solar cells. This paper describes the correlation between microstructure and electronic properties of photoactive TiO2 and ZnO thin films, which are based on experimental data and are interpreted by ab-initio simulations. This study considers the influence of three main factors on the optical and electrical properties: Strain of epitaxially grown thin films, nano-particle- and nano-pore- structures, and finally the interface to adsorbed dye molecules. The first part describes the search for a suitable substrate to grow titania layers with a smaller band-gap and ab-initio simulations showed excellent agreement to the experimental data. A narrow band gap is predicted for strained lattice constants in the a-direction and compressed in the c-direction. The second part describes the fabrication of nano-porous thin films by sol-gel processing using appropriate precursor solutions (titanium-tetra-iso-propanol (TTIP), di-ethanol-amine (DEA)) applied on suitable nano-templates. Due to the surface curvatures the nano-porous TiO2 has a narrow band gap, while nano-particles of titania show a larger band-gap. In the third part Dvxα ab-initio simulations were applied to dye-sensitized solar cells (DSSC), based on ZnO and TiO2. The results are compared to experimental data obtained for different dyes on nanoporous electrodeposited ZnO films. The ranking in efficiency found experimentally for the different combinations could be explained by the calculation results. This finding is discussed in the view of further optimization of solar cells.
KW - Ab-initio calculations
KW - Band gap
KW - Dye-sensitized solar cells
KW - Electronic orbitals
KW - Epitaxial thin films
KW - Nano-porous titania
KW - Photo-catalyst
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M3 - Article
AN - SCOPUS:12344332344
VL - 5
SP - 343
EP - 354
JO - Journal of Ceramic Processing Research
JF - Journal of Ceramic Processing Research
SN - 1229-9162
IS - 4
ER -