Design And Synthesis Of Copper (Ⅰ)-based Dyes With The Conformation Restriction And Their Application In Dye-sensitized Solar Cells

The luminescent properties of transition metal complexes have garnered muchattention due to their applications in photochemical catalysts, light-emitting diode,dye-sensitized solar cells. In particular, the design and construction of Cu+complexesas sensitizers in dye-sensitized solar cells has been one of the most active researchsubjects. The reaction of Cu+salt with organophosphine ligands and pyridine-typeligands afforded Cu+complexes [Cu2(pmb)(PPh3)4](BF4)2(1),{[Cu2(pmb)(CH3CN)2(PPh3)2](ClO4)2}{[Cu2(pmb)(CH3CN)2(PPh3)2](ClO4)2}(2),[Cu2(pmbb)(CH3CN)2(PPh3)2](BF4)22DMF (3),[Cu2(pmbb)(CH3CN)2(PPh3)2](ClO4)22DMF(4),[Cu2(pmb)(PPh3)2(Cl)2](5),[Cu2(pmbb)(PPh3)2(Cl)2](6),[Cu2(pfan)2(4,4’-bipy)(PPh3)2](BF4)2(7),[Cu2(4,4’-bipy)(2,2’-bipy)2(PPh3)2](BF4)2(8),[Cu2(bpe)(2,2’-bipy)2(PPh3)2](BF4)2(9),[Cu2(bpe)(phen)(PPh3)2](BF4)2(10),[Cu2(bpe)(pfan)2(PPh3)2](BF4)2(11),[Cu2(pmb)(dppe)2](BF4)2(12),[Cu2(pmb)(dppp)2](BF4)2(13),[Cu2(pmb)(pba)2](BF4)2(14) and [Cu2(pmbb)(pba)2](BF4)2(15). Thesecomplexes were characterized by IR,1H NMR,13C NMR,31P NMR,19F NMR,11BNMR, UV-Vis spectrum, fluorescence spectra, thermogravimetric analysis and X-raycrystal structure analysis. In addition, sensitization mechanisms of12and13onanatase TiO2(101) surface are observed, and complexes12-15were used indye-sensitized solar cells.DFT calculations and experiments of1-6show that the anions play an essential rolein the stability of copper (I) complexes. The stability order of the anions isBF4->Cl->ClO4-. In7-11, intermolecular stacking interactios likely caused asubstantial decrease in of the molar extinction coefficient, thereby reducing therelative intensities of fluorescence and phosphorescence, and affect the quantum yieldof complexes, respectively. Conjugated units are responsible for greater rigidity andmore conducive to the accumulation of copper (I)-based dyes. The rigidity order ofchelating ligands is phen>2,2’-bipy>pfan. The rigidity and size order of bridgingligands is4,4’-bipy>bpe. In12-15, organophosphine ligands are responsible forgreater rigidity, smaller size, higher coordination number, and decreased the HOMOenergy. The rigidity order of organophosphine ligands is pba>dppe>dppp>PPh3. More,the pyridine-type ligands are responsible for higher conjugation, more flexible andsmaller size, especially in reducing the LUMO energy. The conjugation order is pmbb>pmb. Sensitization mechanisms of12and13on anatase TiO2(101) surface display thatthe nanocrystalline TiO2(101) adsorbing12and13is unstable. Because sensitizersare not attached by carboxylic acid anchor groups to anatase TiO2(101) surface. Theorbital compositions of HOMO and LUMO do not change significantly before andafter the adsorption of12and13on TiO2anatase (101) surfaces. The LUMOs of thecopper (I)-based dyes is larger than that of the nanocrystalline TiO2, which have thelarger light harvesting efficiency and the larger number of electrons injected to theconduction band of TiO2.Complexes12-15as sensitizers show that concerning complexes with identicalpyridine-type ligands but different phosphine ligands, the tendency toward increasedquantum yield and lifetime, as well as for reduced non-radiative transitions, goes withthe increase in size and rigidity of the phosphine ligands, which produces the moreefficient dye with a relative energy efficiency. The energy efficiency order of thecopper (I)-based dyes is η12>η14>η13>η15. Similarly, concerning complexes withidentical phosphine ligands but different pyridine-type ligands, the radiative kr values,lifetime and quantum yield exhibit a marked decrease with the size increase ofpyridine-type ligands, producing the worse efficient dye with a relative energyefficiency (η12>η13and η14>η15).