Theoretical studies of the suitability of imidazolypyridine as bidentate ligands for copper redox couples in the Dye Sensitized Solar Cell (DSSC) application
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Date
2025-12-19
Journal Title
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Publisher
Research Square
Abstract
Copper complex redox couples have emerged as alternative redox mediator to iodide/triiodide
redox couple for DSSC devices. The copper redox couples enable high and tunable voltage in
DSSC devices. However, the Cu(II) species in a typical copper redox couples are strongly
electrophilic towards injected electrons in TiO2 thereby promoting recombination and decreases
the cell performance. Although 4-tertbutylpyridine (TBP) passivation of TiO2 surface reduces the
extent of the recombination, its interaction with Cu(I) complex in a copper redox couples may be
detrimental to the cell performance. Therefore, rational selection of ligands of the copper
complexes is critical in obtaining high voltage and performance. In this work, Density Functional
Theory (DFT) was adopted to screen four imidazoly-pyridine bidentate ligands: 2-(1-methyl-4,5-
dihydro-1H-imidazol-2-yl)pyridine (MDIP); 2-(1-methyl-1H-imidazol-2-yl)pyridine (MIP); 2-
(1,4,5-trimethyl-1H-imidazol-2-yl)pyridine (TMIP) and 1-methyl-2-(pyridin-2-yl)-1Hbenzo[
d]imidazole (MPBI). Calculated binding constants of interaction of 4-tertbutylpyridine
(TBP) with the imidazoly-pyridine copper complexes indicated Cu(I) complexes of MDIP and
MIP interact strongly with TBP. This has adverse effects on device voltage, thus, making MDIP
and MIP ligand unsuitable. But Cu(I) complexes of TMIP and MPBI interact very weakly with
TBP, indicating they are suitable ligands for copper complex redox couples for DSSC application