| Based on the principle of crystal engineering, we have mainly studied the syntheses, crystal structures, the luminescent properties of zinc and cadmium blue light emitting materials and application in dye-sensitized solar cells. In this paper, 21 novel zinc and cadmium complexes having different types of nitrogen heterocyclic ligands as main ligands, aromatic dicarboxylic acid as auxiliary ligands have been hydro(solvo)thermally synthesized and characterized by single-crystal X-ray diffraction, IR, elemental analysis, 1H NMR spectra and powder X-ray diffraction. Zinc and cadmium complexes from zero to one dimensional chain(2 cases), two-dimensional layer(9 cases) and three-dimensional network structures(8 cases) have been successfully designed. Their properties have been researched by thermal gravimetric analyses, solution and solid luminescent analysized. The target is to clarify how subtle structural changes modulate the luminescence features, further revealing the structure-property relationship. Considering these complexes with a large conjugated system which is conducive to electronic transmission performance, it is an effective way to choose them as co-sensitizers used in dye sensitized solar cells. Compared with traditional ruthenium dye N719 sensitized solar cells existed the problems of weak absorption in the blue violet region, these complexes as co-sensitizers can overcome the lack of absorption by N719 in the low wavelength region of the visible spectrum and offset the competitive visible light absorption of I3- to improve the performance of ruthenium dye sensitized solar cells.In the preliminary experiment, three novel 3D Cd(II) complexes, {[Cd(IN)2]·H2O}n(1), [Cd2(IN)2(SO4)(DMF)2]n(2) and {[Cd3(IN)5.5]·0.5OH-}n(3) are obtained by isonicotinic acid ligand(HIN) via solvothermal reactions, which realized the topological structures convert from three-dimensional rtl to ncd type by a simple temperature induced single crystal to single crystal transition. Complexes 1–3 display luminescence with emission maxima from 398 to 435 nm contained deep blue, blue, light blue and green in the solid state, protic solvent and protic solvent.In the following chapter, quinoline-3-carboxylic acid(3-Hqlc) as N-heterocyclic carboxylate ligand with a relatively large π-conjugated system is selected as main ligands. One stable blue emission 2D Cd(II) complex [Cd(3-qlc)2]n(4) has been synthesized with excellent aggregation-induced emission(AIE) properties in DMSO/water mixtures. The luminescence intensity of complex 4 in the DMSO/water mixture with 99 vol% H2 O is 5.43-fold higher than that in DMSO solution. Encouraged by the UV-visible absorption in an ethanol solution result, complex 4 sensitized device exhibited η value of 7.70%(Jsc = 18.36 m A cm–2, Voc = 0.72 V, and FF = 0.58), which is 43.66% higher than that of cells individually sensitized by N719.In order to seek for higher conversion efficiency of dye sensitized solar cells, the introduction of linear nitrogen heterocyclic ligand 4-(1H-imidazol-1-yl)benzoic acid(4-HIBA) in the reaction system led to form two-dimensional and zero dimensional complexes, [Cd3(IBA)3(Cl)2(HCOO)(H2O)]n(5) and {[Cd1.5(IBA)3(H2O)6]·3.5H2O}n(6). The DSSC devices using complexes 5 and 6 have obtained the overall conversion efficiency of 8.27% and 7.73% through improving the preparation of cells technology.Considering the rigid ligands and flexible ligands influence on structure and performance, six cadmium complexes from a mononuclear to three-dimensional structures have been synthesized by a new design of 4-cyanobenzyl-based 1,2,4-triazole ligand 4-(1,2,4-triazolylmethyl) cyanobenzene(TMCB), formulated as [Cd(TMCBA)2]n(7), [Cd(TMCB)(1,4-bda)(H2O)]n(8), {[Cd2(TMCB)4(1,4-bda)2(H2O)2]n·3H2O}n(9), {[Cd(TMCB)4(H2O)2]·(NO3)2·(H2O)2}n(10), [Cd1.5(1,4–bda)1.5(DMF)2]2n(11), [Cd1.5(1,4–bda)1.5(DMF)2]2n(12). Due to center metal Cd(II) adopting different coordinate modes to form various structures, the luminescence emission of complexes 7–12 make significant differences. Meanwhile, the overall conversion efficiency of complexes 7 and 10 were found to be 7.68% and 6.85%. Compared with the rigid ligands to construct complexes, flexible complexes as co-sensitizers of photoelectric conversion efficiency is slightly lower.Focusing on more flexible 1,3-bis-(imidazol-1-ylmethyl)benzene(mbix) and 1,4-bis-(imidazol-1-ylmethyl)benzene(pbix) as main ligands; oxalic acid(H2ox), 1,4-benzenedicarboxylic acid(1,4-H2bda) and thiophene-2,5-dicarboxylic acid(2,5-H2tdad) as auxiliary ligands, a series of zinc and cadmium complexes [Cd(mbix)(2,5-tdad)]·H2O}n(13), [Cd(mbix)(1,4-bda)(H2O)]n(14), [Cd(mbix)(Cl)2]n(15),{[Zn(mbix)2]n·(NO3)2·3H2O}n(16), {[Zn2(mbix)2(2,5-tdad)2]·H2O}n(17), {[Zn4(mbix)4(2,5-tdad)4]·H2O}n(18), [Zn2(mbix)(1,4-bda)0.5(ox)1.5]n(19), [Zn1.5(pbix)0.5(1,4-bda)1.5]n(20), {[Cd2(bib)2(2,2′-bpda)2]·2H2O}n(21) have been obtained. The relationship between crystal structures and luminescent properties reveals that atomic radius, conjugation degree and the coordination modes of ligands have important influences on the luminescent properties. |
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