TiO₂ Band Shift by Nitrogen-Containing Heterocycles in Dye-Sensitized Solar Cells:  a Periodic Density Functional Theory Study

Abstract

A density functional theory (DFT) method (periodic DMol3) with full geometry optimization was used to study the adsorption of nitrogen-containing heterocycles such as pyrazole, imidazole, 1,2,4-triazole, pyridine, pyrimidine, pyrazine, and 4-t-butylpyridine (TBP) on TiO2 anatase (101), (100), and (001) surfaces. All structures displayed a negative shift in the TiO2 Fermi level upon adsorption of N-containing heterocycles. Additionally, the heterocycles were examined as an additive in an I-/I3- redox electrolyte solution of dye-sensitized TiO2 solar cell. The DFT results indicated that the negative shift of TiO2 Fermi level was due to the adsorbate dipole moment component normal to the TiO2 surface plane, and corresponded to the enhanced open-circuit photovoltage (Voc) and the reduced short-circuit photocurrent density (Jsc) in a dye-sensitized solar cell.

Chemical and photochemical degradation of polybrominated diphenyl ethers in liquid systems – A review

“…6 a) (Sun et al 2008). Generally, theadsorption of bases on the surface of TiO 2 shifts the Fermi level (flat band potential) 609 toward a negative potential; on the contrary the adsorption of acids tends to positively 610 shift the conduction band edge (Kusama et al 2008, Sun et al 2008, Ward et al 1983. 611…”

Bridging the Fields of Solar Cell and Battery Research to Develop High-Performance Anodes for Photoelectrochemical Cells and Metal Ion Batteries

“…Nitrogen-containing heterocyclic molecules have been shown to modify the open circuit voltage and the short circuit current depending on the molecular and surface structure [76]. We therefore suggest calculations of a series of imidazole derivatives adsorbed on TiO 2 (such as imidazole, 4-phenylimidazole and 2-iso-propenylimidazole).…”

“…Most previous computational studies of the interaction of co-adsorbent molecules or atoms/ions with TiO 2 were done for bulk or for extended low-index surfaces [53,76,107]. It is known that nanosizing significantly changes the electronic properties of TiO 2 anodes (including suppression of first order phase transitions and a large irreversible loss of Li capacity upon the first cycle) [38,84,90,107].…”

“…This will identify structure-property relations, which will guide the experimental design of improved solar cells and batteries. We suggest imidazole derivatives for this study, as this kind of molecules has been used to improve DSSC performance [76,77] and they are known to be compatible with Li battery components [78]. Structural changes of the nanocrystalline TiO 2 anode due to the insertion of counterions, such as Li + or Na + , will then be studied.…”

Effect of Ionic Liquids with Different Cations in I-/I3-Redox Electrolyte on the Performance of Dye-sensitized Solar Cells

“…Ionic liquids (ILs) were first used in DSCs in Grätzel's laboratory, with the primary aim of preventing voltage drop by the Li + and K + ions because the IL cations can replace the absorption sites on the TiO 2 surface. [4][5][6][7] The first IL tested in DSC was based on the imidazolium cation, and subsequently, ILs based on this family have been widely used in electrolytes for DSCs. Room temperature ionic liquids are important because of their special properties, such as good chemical and thermal stability, wide electrochemical window, negligible vapor pressure, non-flammability and high ionic conductivity.…”