Study Of Photovoltaic And Ferroelectric Function Materials Based On Triphenylamine Derivates

In the 21st century,people place higher and higher require on new energy and information materials,which also promote the rapid development of science and technology in this field.Dye-sensitized solar cells(DSSCs)are currently under intense academic and industrial investigations,because of their environmentally-friendly,efficient,and low-cost features.In the field of information materials,molecular-ferroelectrics have advantages of fine plasticity,structural diversity,easy processability,therefore its bistable state can be used to develop ferroelectric information storage element.This work is considered as an important storage technology of the 21st century,which has important theory value and application prospect.With features of low-cost,easy structural modification,convenient synthesis process,et al,triphenylamine derivatives are ideal precursors to construct photovoltaic and ferroelectric materials.On the one hand,triphenylamine unit has strong electron-donating and hole transport ability,and its propeller-shaped structure would help to reduce electron recombination probability.In recent years,triarylamine dyes based DSSCs attracted much academic attention.On the other hand,with asymmetric induction effect,asymmetric N-containing triarylamine ligand can be used to construct ferroelectric coordination polymers.In this dissertation,starting from triarylamine unit,we fabricated a series of dye sensitizers and ferroelectric coordination polymers.Their photovoltaic and ferroelectric performances were tested.Meanwhile,their structure-function relationships were studied via investigation of various physical and chemical properties.The main contents are listed below:1.Different heterocyclic substituted triphenylamine groups were firstly screened to be electron donors of sensitizers,and we wish that this work can provide guidance to further design triarylamine dyes.Three novel triarylamine dyes named TTC101,TTC102 and TTC103,were synthesized economically through modifying the structure of a simple triarylamine dye(TC105)using three kinds of heterocyclic groups(4-pyridyl,2-thienyl and 1-pyrazolyl).The overall solar-to-electrical energy conversion efficiencies(?)of TTC102 and TTC103 are 4.92%and 5.21%respectively under AM1.5G irradiation,reaching 1.29 and 1.37 times of the efficiencie of TC105 respectively.These results demonstrate that the photovoltaic performance can be improved after introducing suitable heterocyclic groups to triarylamine dyes.4,4'-Di(2-thienyl)triphenylamine moiety,included in dye TTC102,has been screen out as an optimal electron donor fragment.The photocurrent density-voltage curves for the DSSCs were recorded under irradiation with different light intensities.Energy conversion efficiencies(?)are increased along with the decrease of light intensity,which would be mostly ascribed to the enhanced Fill Factors.Series of properties were investigated to explain the results.The more charge recombination rate may partly result in the existence of the wide gap(0.057 V)between the open-circuit voltages of TTC102 and TTC103.2.We adopted 4,4'-di(2-thienyl)triphenylamine moiety as electron donor fragment,9-ethyl-3,6-di(2-thiophenyl)carbazole moiety as 7r-conjugated bridge or secondary electron donor moiety,cyanoacetic acid and 4-pyridyl group as electron acceptors.Then,two novel dyes TTC104 and TTC105 were synthesized.After anchoring on TiO2 nanoparticle film,the absorption band of TTC104 is broader by 30 nm than that of TTC102.Under AM 1.5G irradiation,energy conversion efficiency(?)of DSSC based on TTC104 reaches 6.36%,which is 21.6%higher than that of TTC102(5.24%).Dye TTC105,containing pyridyl group as the electron acceptor,showed only 1.88%conversion efficiency(?)when used in DSSCs.The huge different performances of TTC104 and TTC105 are improved to be partly due to the smaller dye loading amount,higher dark current and charge recombination rate of TTC105.3.Porphyrins are promising candidates as highly efficient sensitizers for DSSCs because of their superior light-harvesting ability in the visible region and mimicking photosynthesis.In this paper,we adopt 4,4'-Di(2-thienyl)triphenylamine and 5-ethynylthiophene-2-carboxylic acid as electron push and pull moieties of porphyrin sensitizer for the first time.Four porphyrin dyes,named ZLD13,ZLD14,ZLD15 and ZLD16,were synthesized and fully characterized.Under AM 1.5G irradiation,energy conversion efficiency(?)of DSSC based on the fundamental dye ZLD13 reaches 3.37%.After introducing 4,4-Di(2-thienyl)triphenylamine or 5-ethynylthiophene-2-carboxylic acid to ZLD13,the energy conversion efficiencies(?)are improved in different degrees.When 4,4'-Di(2-thienyl)triphenylamine and 5-ethynylthiophene-2-carboxylic acid were both introduced to the porphyrin dye,energy conversion efficiency(?)is further enhanced to 6.12%(ZLD 16),which is comparable with N719-based reference cell under the same conditions.The above results indicate that 4,4'-di(2-thienyl)triphenylamine moiety and 5-ethynylthiophene-2-carboxylic moiety are ideal push-pull moieties of porphyrin dyes.Series of properties were investigated to explain the results,laying a special emphasis on the energetics,dark currents,and electrochemical impedance spectroscopy to study charge transfer processes at the dye/titania/electrolyte interface.4.To study the molecular-ferroelectrics,we designed and synthesized two asymmetrical ligands(DIMPPA and MIDPPA).The coordination reactions under solvothermal conditions of DIMPPA or MIDPPA,various carboxylic ligands and metal ions produce five new chiral coordination polymers 1L,1R,2,3 and 4.Thereinto,1L and 1R are highly rare enantiomers with novel topology types.Compound 2 shows two fold chiral interpenetrating framework.Compounds 3 and 4 exhibit chiral 2D ? 3D inclined polycatenation structures.Ferroelectric properties indicated that 1L and 1R are promising good candidates for ferroelectric materials.The related circular dichroism(CD)spectroscopy,second-order nonlinear optic(NLO),and fluorescent properties were also studied.This work provides us with useful clues to further explore ferroelectric metal-organic frameworks based on achiral ligands.