Speaker
Dr
Eric Maluta
(University of Venda)
Description
Theoretical and computational studies of doped TiO2 polymorphous can contribute to a deeper understanding of dye sensitized solar cells. These solar cells represent a promising approach to a direct conversion of sunlight into electrical energy at low cost and with high efficiency. The light adsorption occurs in dye molecules adsorbed on a highly porous structure of TiO2 film [1-2]. The problem encountered with the TiO2 is its wide band gap which is about 3.4 eV and show photocatalytic activity under UV light irradiation that accounts for only a small portion of solar energy, in contrast to visible light which has a major part of solar energy. Harnessing and effectively utilizing sunlight is the most challenging subject for the extensive application of TiO2 as photon absorption [3]. Transition metal doping is one of the most effective approaches to extend the absorption edge of TiO2 to visible light region, which either inserts a new band into the original band gap, or modification of the conduction band (CB) or valence band (VB) improving the photocatalytic activity of TiO2 to some degree [3-5].
In the current study, electronic density of states and optical properties of doped and undoped, Anatase and Brookite surfaces were performed using the first-principles calculations based on Density Functional Theory (DFT) using a plane-wave pseudopotential method. The generalized gradient approximation (GGA) was employed in the scheme of Perdew-Burke-Ernzerhof (PBE) to describe the exchange-correlation functional. All calculations were carried out with CASTEP (Cambridge Sequential Total Energy Package) code in Materials Studio of Accelrys Inc [6]. The results confirm that the mixing of the dopants induced states with the original Ti 3d and O 2p valence band and conduction band attributes to the band gap, hence the shifting of the absorption edge of TiO2 from UV to visible spectrum. The light harvesting efficiency of the dye molecules were calculated and compared to the experimental values.
Keywords: Dye sensitized solar cells, Density Functional theory, Bandgap, Optical and Electronic Properties.
References
1. Chou T.P., Zhang Q., Cao G., (2007), Effects of dye loading conditions on the energy conversion efficiency of ZnO and TiO2 dye-sensitized solar cells. Journal of Physical Chemistry C, 111, 18804-18811.
2. Yuasa T., Kawakami R., Sato Y., Mori Y., Adachi, M., Yoshikado, S., (2012), Dye adsorption for dye-sensitized solar cell, Solar Energy Materials and Solar Cells, 102, 2-7.
3. Zallen R, and Moret M.P. The optical absorption edge of brookite TiO2. Solid State Commun, 2006, 137 154-157.
4. Yang K, Dai Y, Huang B, Han S: Theoretical study of N-doped TiO2 rutile crystals. J Phys Chem B 2006, 110:24011–24014.
5. Grätzel M, and O’Regan B. “A Low-Cost, High-Efficiency Solar Cell Based on dye sensitized Colloidal TiO2 Films” Nature, 353, 737-740, 1991.
6. Clark S.J, Segall M.D, Pickard C.J, Hasnip P.J, Probert M.I.J, Refson K and Payne M.C 2005 Z Kristallogr 220 567–570.
HPC content
First-principles calculations based on Density Functional Theory (DFT) using a plane-wave pseudopotential method. The generalized gradient approximation (GGA) was employed in the scheme of Perdew-Burke-Ernzerhof (PBE) to describe the exchange-correlation functional. All calculations were carried out with CASTEP (Cambridge Sequential Total Energy Package) code in Materials Studio of Accelrys Inc [6]
Primary author
Dr
Eric Maluta
(University of Venda)
Co-authors
Mrs
Ife Fortunate Elegbeleye
(Physics department, University of Venda)
Prof.
Regina Maphanga
(CSIR)
Mr
Tshifhiwa Steven Ranwaha
(University of Venda)
Mr
ratshilumela steve dima
(university of venda)
