Investigation Of The Influence Of Electron Acceptor Groups And ? Bridges On The Porphyrin Sensitizers

In this work,the structure-property relationship of porphyrins was studied.We designed and synthesized two types of porphyrin sensitizers:A series of D-A-?-A porphyrins with thiophene?-bridge and fluorin named as TH porphyrins and a series of LX porphyrins that were based on cyano group and extended?-bridge in the acceptor.These dyes were introduced in DSSC to investigate their photovoltaic performance.The free base porphyrin was obtained by dipyrrole,aldehyde through Lindsey porphyrin thynthesis.The subsequent bromination with NBS and metalation with Zn?OAc?₂·2H₂O gave[5,15-bis?2,6-bis?octyloxy?phenyl?-10-bromo porphyrinato]zinc?II?11.[5-Bromo-10,20-bis?2,6-di-octoxyphenyl?-15-?4-?N,N-dioctylaniline?phenylethynyl?porphrinato]zinc?II?14 was synthesized through coupling and hydrolysis of triisopropylsilylacetylene with donor moiety.Similar process afforded in[5-?4-?N,N-dioctylaniline?phenylethynyl?-10,20-bis?2,6-di-octoxyphenyl?-15-?5-?7-ethynyl-benzo[c][1,2,5]thiadiazol?-thiophene-2-carboxylate?porphrinato]zinc?II?16a,16b and 16c.Further hydrolysis gave target porphyrins.Specific structural confirmation was performed by MALDI-Tof and ¹H-NMR for these dyes.All the dyes were used as sensitizers in DSSC gave insights into their photovoltaic properities after testing photophysical and electrchemical properties.We found that the substitution of fluorine on the benzothiadiazole facilitate the light-harvesting ability and prolong electron lifetime,thus TH-2F with two fluorines outperformed among these three dyes with photoelectric transformation efficiency?PCE?of6.98%,short-circuit current(J_sc)of 16.07 mA/cm²,open circuit voltage(V_oc)of 0.68V and fill factor?FF?of 63%?The free base porphyrin was obtained by dipyrrole,benzaldehyde and 4-?di?1H-pyrrol-2-yl?methyl?phenyl acetate by MacDonald[2+2]method.LX porphyrins with 4-butoxy phenyl as donor group and acrylic acid,a-cyanoacrylic acid,and a-cyanopentadienoic acid as acceptor respectively,were subsequently obtained by bromination,reduction,oxidation,Knoevenagel reaction.Specific structural confirmation was performed by MALDI-Tof and ¹H-NMR for these dyes.All the dyes were used as sensitizers in DSSC to give insights into their photovoltaic properities after testing photophysical and electrchemical properties.The results suggest that introducing the–CN group into the acceptor and extending the conjugation of the?-bridge may lead to weak interfacial coupling,low electron injection driving force,low Jsc,and thus low PCE.The best performance was found in LX1 with J_scc of 11.67 mA/cm²,V_occ of 0.73 V,FF of 71%,PCE of 6.04%.