An insight into the controllable synthesis of Cd(II) complexes with a new multifunctional ligand and its application in dye-sensitized solar cells and luminescence properties

摘要

Based on a new design of 4-cyanobenzyl-based 1,2,4-triazole ligand 4-(1,2,4-triazolylmethyl) cyanobenzene (TMCB), a series of cadmium complexes 1-5 ' from a mononuclear to three-dimensional (3D) structure have been synthesized through hydro(solvo) thermal reactions; they were generally formulated as [Cd(TMCBA)(2)](n) (1), [Cd(TMCB)(1,4-bda)(H2O)](n) (2), {[Cd-2(TMCB)(4)(1,4-bda)(2)(H2O)(2)](n)center dot 3H(2)O}(n) (3), {[Cd(TMCB)(4)(H2O)(2)]center dot(NO3)(2)center dot(H2O)(2)}(n) (4), [Cd-1.5(1,4-bda)(1.5)(DMF)(2)](2n) (5) and [Cd-1.5(1,4-bda)(1.5)(DMF)(2)](2n) (50) (TMCBA = 4-(1,2,4-triazolylmethyl) benzoic acid, which is formed from the hydrolysis of TMCB; 1,4-H(2)bda = 1,4-benzenedicarboxylic acid; the difference between two genuine supramolecular isomers of 5 and 50 is the use of TMCB as the additive agent for the reaction). Complexes 1-5' exhibit tunable luminescence with emission maxima containing deep blue, blue, light blue, green and deep green region at 298 K or 77 K in both different solvents (polarity: DMSO > CH3OH > CHCl3) and solid state. Interestingly, the good thermal stability accompanied by their compensated adsorption to ruthenium complex N719 in the region of low wavelength, enabled 1 and 4 to serve as co-sensitizers in combination with N719 in dye sensitized solar cells (DSSCs). After co-sensitization with N719, the overall conversion efficiency of 1 and 4 were found to be 7.68% and 6.85%, which are 40.40% and 25.23% higher than that for DSSCs only sensitized by N719 (5.47%) under the same conditions, respectively. The improvement in efficiency is attributed to the fact that complexes 1 and 4 overcome the deficiency of N719 absorption in the low wavelength region of ultraviolet and blue-violet, offset competitive visible light absorption of I-3(-) and reduce charge recombination due to the formation of an effective cover layer of the dye molecules on the TiO2 surface. As a result, the synthesized complexes are promising candidates as co-adsorbents and co-sensitizers for highly efficient DSSCs.