Solvatochromic and application in dye-sensitized solar cells of sandwich-like Cd(ii) complexes: supramolecular architectures based on N1,N3-bis[(6-methoxypyridin-2-yl)methylene]benzene-1,3-diamine

Abstract

A novel polydentate Schiff base ligand N¹,N³-bis[(6-methoxypyridin-2-yl)methylene]benzene-1,3-diamine (L) and its two dinuclear sandwich-like complexes {[CdL(NO₃)(H₂O)]·NO₃}₂ (1) and {[CdL(CH₃CN)(H₂O)]·(ClO₄)₂·(CH₃CN)₂}₂ (2) were synthesized. Both C–H⋯O, C–H⋯N and π–π non-covalent interactions had essential roles in constructing the resulting three-dimensional supramolecular networks. L emits a more intense blue-green fluorescence emission around 493 nm than in dilute solution, exhibiting stacking-induced emission properties. Complexes 1 and 2 exhibited the dual properties of exceptional solvatochromism and fluorescence quenching towards CH₃OH molecules. As these compounds could overcome the absent absorption of ruthenium complex N719 in the low wavelength region of the visible spectrum, offset the competitive visible light absorption of I₃⁻ and reduce the charge recombination of injected electrons, the Schiff base ligand L and complexes 1 and 2 were used as co-sensitizers in combination with N719 to investigate their effect on enhancing the performance of dye-sensitized solar cells. A short circuit current density of 14.37 mA cm⁻², an open-circuit voltage of 0.71 V and a fill factor of 0.61 corresponding to an overall conversion efficiency of 6.17% under AM 1.5 G solar irradiation were achieved when 1 was used as a co-sensitizer, which are much higher than the results obtained for dye-sensitized solar cells sensitized by N719 alone (5.06%).