Synthesis And Photovoltaic Performance Of D-?-A Asymmetric Porphyrin-thiophene Derivatives

Due to the delocalized ?-conjugated system and strong absorption in the visible region,porphyrin derivatives attract extensive attention for the great potential as organic photoelectronic materials.To develop novel photovoltaic materials based on porphyrin derivatives,herein,we designed and synthesized a series of asymmetric porphyrin-thiophene derivatives: 5-oligothiophenyl-10,15,20-tris(4-(dodecyloxy)phenyl)porphyrin(Por-n T),5-([5'/5''-formyl-2-oligothiophenyl]-5-yl)-10,15,20-tris(4-(dodecyloxy)phenyl)porphyrin(Porn TCHO),5-([5'/5''-dicyanovinyl-2-oligothiophenyl]-5-yl)-10,15,20-tris(4-(dodecyloxy)phenyl)porphyrin(Por-n T2CN)and zinc(II)-5-([5'/5''-dicyanovinyl-2-oligothiophenyl]-5-yl)-10,15,20-tris(4-(dodecyloxy)phenyl)porphyrin(PZn-n T2CN)(n=2,3).They were all accurately charactered by MS,1H/13 C NMR and FT-IR.The molecular structures are depicted below:By means of thermogravimetric analysis,the results revealed that the porphyrin derivatives with D-?-A configuration were more stable.In the meanwhile,ultraviolet-visible spectrophotometer,electrochemical workstation and fluorescence spectrophotometer were also used to investigate the photoelectric performance of these asymmetric porphyrins.On the basis of photoelectronic studies above,four D-?-A asymmetric porphyrin-thiophene derivatives were vacuum-evaporated as donor materials into bilayer heterojunction(Bi HJ)photovoltaic devices,together with the acceptor 3,4,9,10-perlenetetracrboxylic dianhydride(PTCDA).It was found that compared with the devices of other prepared D-?-A asymmetric porphyrin-thiophene derivatives,the device based on PZn-3T2 CN showed the best performance.When treated with solvent vapor annealing(SVA)and thermal annealing(TA),the device was improved to some extent by pyridine vapor and the optimized duration was 1h.With the addition of 4,4'-bipyridine,the active layer of Bi HJ device based on PZn-3T2 CN tends to stack more orderly and closely,thus enhancing the device performance.Ethanol treatment further improved the PCE from 0.38% to 1.14%.