Study On Synthesis And Photoelectric Performance Of Double-donor Carbazole Dye Sensitizer

Dye sensitized solar cells（DSSC）,which can achieve the photovoltaic energy conversion at low cost,has attracted a lot of attention recently.The sensitizer,acting as a light harvesting antenna,plays an important role in the collection of light and the electron generation/transfer.Three series of seven kinds of carbazole sensitizer were designed and synthesized with carbazole derivatives as the electron donor,fluorenone or coumarin as auxiliary donor,aromatic ring as a conjugated bridge,cyanoacetic acid or benzoic acid as the electron acceptor.The molecular structures were characterized by NMR and MS and the reaction mechanism was studied.The spectral properties,electrochemical properties and photovoltaic performance of the dye sensitizer were measured,and the relationship between structure and properties is studied systematically.Three novel D-D-π-A carbazole sensitizers were designed and synthesized with carbazole derivatives as the electron donor,fluorenone as the auxiliary donor,benzene,furan or thiophene asπbridges respectively,cyanoacetic acid as the electron acceptor.The intermediate carbazole boronic ester was prepared through the reaction of3-bromo carbazole derivatives and boric acid trimethyl ester under the catalysis of butyl lithium,which reacted successively with dibromofluorenone,4-formyl benzene boric acid or 5-formyl furan boric acid through Suzuki coupling to afford the aldehydes.The aldehydes reacted with cyanoacetic acid through Knoevenagel condensation to get compounds HXL-1B and HXL-2F.HXL-3S was synthesized through the coupling of carbazole boronic ester with dibromine fluorenone,2-thiophene boric acid,the introduction of an aldehyde group on the thiophene ring,and the Knoevenagel condensation between the aldehyde and cyanoacetic acid.Through the measurement of the spectral properties and photovoltaic performance and theoretical calculation of HXL-1B～HXL-3S,it is found that HXL-1B with phenyl asπbridge exhibits the highest photoelectric conversion efficiency 4.88%（Jsc=8.36m A/cm²,Voc=0.67 V,FF=8.66）.Two carbazole sensitizers with benzoic acid acceptor were designed and synthesized with N-butyl carbazole as the electron donor,fluorenone as auxiliary donor andπbridge,benzoic acid as the electron acceptor.N-butyl 3-bromocarbazoles reacted with boric acid trimethyl ester in the presence of butyl lithium to give the corresponding carbazole boronic acid ester.HXL-4W and HXL-5Z were synthesized through the successive coupling reaction of the carbazole boronic acid ester with 3,6-dibromofluorenone or 2,7-dibromofluorenone and then with4-carboxyphenylboronic acid.Through the measurement of the spectral properties and photovoltaic performance and theoretical calculation of HXL-4W and HXL-5Z,the results show that HXL-5Z bearing 2,7-substituted fluorenone with carbazole donor and benzoic acid receptor exhibits better photo-electricity conversion efficiency2.03%（Jsc=3.88 m A/cm²,Voc=0.70 V,FF=0.75）。Two carbazole sensitizers were designed and synthesized with N-butyl carbazole or N-phenyl carbazole as the electron donor,coumarin as auxiliary donor,thiophene asπbridges,cyanoacetic acid as the electron acceptor.N-substituted bromocarbazole reacted with boric acid trimethyl ester in the presence of butyl lithium to afford the carbazole boronic acid ester which coupled with the 6-bromo-3-thiophene coumarin.The intermediate aldehyde obtained through the introduction of an aldehyde group on the thiophene ring by Vilsmeier reaction reacted with cyanoacetic acid by Knoevenagel condensation to get compounds HXL-6B and HXL-7D.Through the measurement of the spectral properties,electrochemical properties and photovoltaic performance of HXL-6B and HXL-7D,the results show that HXL-7D with N-butyl carbazole as the donor,coumarin as auxiliary donor,thiophene asπbridge,cyanoacetic acid as electron acceptor exhibits higher photoelectric conversion efficiency 2.48%(Jsc=6.06 m A·cm^-2,Voc=0.60 V,FF=0.68).