Novel ruthenium sensitizers with a dianionic tridentate ligand for dye-sensitized solar cells: the relationship between the solar cell performances and the electron-withdrawing ability of substituents on the ligand

Abstract

Five novel ruthenium sensitizers (TUS sensitizers) with a dianionic tridentate ligand (pyridine-2,6-dicarboxyamidato and its derivatives) have been synthesized for application to dye-sensitized solar cells (DSCs). These TUS sensitizers have much larger molar absorption coefficients in the wavelength range below 600 nm compared with those of Black dye which is a structural analog and a highly efficient ruthenium sensitizer. The energy levels of HOMOs and LUMOs of TUS sensitizers shifted to the positive direction with increasing the electron-withdrawing ability of the substituents on the dianionic tridentate ligand. The energy levels of HOMO and LUMO showed linear correlation with respect to the Hammett constant of the substituents. The DSCs with TUS sensitizers showed much lower performances than that of Black dye. Both inferior adsorptivity on the TiO2 surface and unfavorable energy levels of HOMOs and LUMOs for the effective electron transfer reactions in the DSCs are considered to be the main reasons for the much lower performances of TUS sensitizers. The conversion efficiency of the DSC with a TUS sensitizer increased with increasing the electron-withdrawing ability of the substituents on the dianionic tridentate ligand. The observed linear relationship between the conversion efficiency and the driving force of the reduction process of the oxidized form of dyes by I(-) suggests that the dye regeneration process is a rate-determining step in the DSCs with TUS sensitizers.

Ruthenium and Osmium Complexes That Bear Functional Azolate Chelates for Dye‐Sensitized Solar Cells

“…These designs include 1,2,3‐triazolyl [Ru(H 3 tctpy)(L2)]63 and [Ru(H 3 tctpy)(bcpy)] 64 Substitution of 2,6‐bis‐carboxylpyridine (bcpy) with a 2,6‐bis‐carboxylamidatopyridine ancillary afforded sensitizer TUS‐33 65. However, testing their performances using a conventional I − /I 3 − electrolyte generates only modest power‐conversion efficiencies.…”

“…[64] Substitution of 2,6-bis-carboxylpyridine (bcpy) with a2 ,6-bis-carboxylamidatopyridine ancillary afforded sensitizer TUS-33. [65] However,t esting their performances using ac onventionalI À /I 3 À electrolyte generates only modest power-conversion efficiencies. The lowered DSSC efficiency was interpreted in terms of poor dye loading and unmatched energy gaps that resulted in unsatisfactory electron injection and/or dye regeneration, respectively.…”

Geometrical structure, electronic and nonlinear optical properties of square‐planar heteroleptic complexes containing bypridine and pyrazine dithiolate derivatives as dye‐sensitized solar cell: A DFT study

“…In the last three decades, the design and synthesis of homoleptic and heteroleptic metal dithiolene complexes have been attracting great interest due to their wide applications in various research fields, such as conductivity and superconductivity, magnetic materials, bioinorganic chemistry, photosensitizers, laser applications (e.g. Q‐switching) and linear or nonlinear optical (NLO) .…”

New D–π–A dyes incorporating dithieno[3,2-b:2′,3′-d]pyrrole (DTP)-based π-spacers for efficient dye-sensitized solar cells

“…1,2 DSSCs can reduce the production cost and exhibit good photovoltaic performances so as to become a good substitute for expensive silicon solar cells. To date, various sensitizers have been used to fabricate highly efficient DSSCs, involving metal complex dyes [3][4][5][6][7][8] and metal-free organic dyes. [9][10][11][12][13][14] Metal-free organic dyes are amenable to structure modication and easy to purify.…”