Syntheses And Photoelectric Performance Of Julolidine Dye Sensitizers

Dye-sensitized Solar Cells?DSSCs?have received the widespread attention around the world due to the advantages of simple manufacture,low cost and environmental friendly.As the core component of DSSCs,dye sensitizers dominate the photoelectric conversion efficiency of DSSCs.Metal-free organic dye sensitizers stand out from other dye sensitizers because of the advantages of simple synthetic process,easy structural modification,high molar absorption coefficient and so on.Julolidine and its derivatives are a kind of nitrogenous polyheteheterocyclic aromatic compounds,which are characteristic of strong electron donating abilities,rigidity and non-coplanar structure,have been widely used in DSSCs.In the Dissertation,three series of 9 novel julolidine dye sensitizers were designed and synthesized.The molecular structure of the dye sensitizers was characterized by NMR and MS.Nine dye sensitizers were assembled into DSSCs,and their photophysical properties,electrochemical properties,photoelectric properties and molecular theoretical calculations were investigated to analyze the relationship between structure and properties.Two D-A julonidine dye sensitizers JQ and JL were designed and synthesized with the electron donor of 8-butoxyl-1,1,7,7-tetramethyl julonidine moieties as electron donor,and the electron acceptor of cyanoacetic acid and rhodamine-3-acetic acid respectively.The lower efficiency of solar cell based on JL with rhodanine-3-acetic acid acceptor is mainly resulted from the broken conjugated chain due to the presence of methylene,which hinders the electron transmission.Compared to the dye sensitizer JL,DSSC based on dye sensitizer JQ obtained higher photoelectric conversion efficiency of 1.00%?Jsc=2.05 m A/cm²,Voc=0.67 V,ff=73.16%?.JQ was co-sensitized with N719 and Z907 respectively.Consequently,the photoelectric conversion efficiency of DSSCs increased from 1.00%to 6.05%and7.48%respectively.JL was co-sensitized with N719 and Z907,respectively,and the photoelectric conversion efficiency increased from 0.52%to 7.02%and 6.55%.After coadsorption with CDCA,the photoelectric conversion efficiency of DSSCs base on dye sensitizer JQ and JL increased from 1.00%and 0.52%to 1.06%and 1.16%,respectively.Three D-?-A julonidine dye sensitizers JXSB,JXSQ and JXSL with8-butoxy-1,1,7,7-tetramethyl julolidine moieties as electron donor,vinyl-thiophene moieties as?bridge,benzoic acid,cyanoacetic acid and rhodanine-3-acetic acid moieties as electron acceptor,respectively.When the benzene ring is introduced into the dye sensitizer JXSB,the twist degree increased and the degree of?conjugation decreased,which weakens the light absorption and reduces the light utilization rate of DSSCs.In the case of dye sensitizer JXSL,the barrier of methylene segment between the five membered ring of rhodanine and carboxyl group leads to the rupture of the conjugated chain,which hinders the electron transmission,resulting in the low photoelectric conversion efficiency of DSSC base on dye sensitizer JXSL.Finally,DSSC based on dye sensitizer JXSQ has better light capture ability and improved charge transmission power,and yield higher photoelectric conversion efficiency of1.58%?Jsc=3.56 m A/cm²,Voc=0.61 V,ff=71.98%?.After co-adsorption with CDCA,the photoelectric conversion efficiency of DSSCs based on dye sensitizers JXSB,JXSQ and JXSL increased from 1.10%,1.58%and 0.23%to 1.56%,2.50%and 0.68%,respectivelyFour D-?-A julonidine dye sensitizers JXFQ,JXBQ,JXBSQ and JXLSQ were synthesized with vinyl-furan,vinyl-benzene,vinyl-thiophene and vinyl-dithiophene moieties as the?bridge respectively and cyanoacetic acid moieties as the electron acceptor.These dye sensitizers were applied to DSSCs and the influence of different aromatic heterocyclic bridges on the photoelectric properties of DSSCs was studied by the comparasion to the dye sensitizers JXSQ.With the introducing of furan into?bridge,the ground state transition energy of JXFQ was increased,the absorption spectrum was blue shifted,and the light capture ability was weakened,resulting in the poor photoelectric performance of DSSC based on dye sensitizer JXFQ.With the introduction of benzene ring into?bridge,the molecular planarity of JXBQ decreased,the?-?accumulation on Ti O₂ surface was inhibited,the charge recombination rate was reduced and the open circuit voltage was increased.The photoelectric performance results of DSSCs base on dye sensitizers JXSQ,JXBSQ and JXLSQ show that the introduction of thiophene and thiophene derivatives in the bridge can enhance the light capture ability of dyes,improve the utilization rate of visible light,and improve the photocurrent of DSSCs.Finally,DSSC based on dye JXLSQ exhibited the highest photoelectric conversion efficiency of 2.01%?Jsc=4.59 m A/cm²,Voc=0.63 V,ff=69.97%?.After coadsorption with CDCA,the photoelectric conversion efficiency of DSSCs based on dyes JXFQ,JXBQ,JXBSQ and JXLSQ increased from 1.06%,1.81%,1.63%and 2.01%to 1.84%,3.05%,2.27%and 2.85%,respectively.