New D-π-A Dyes Incorporating Dithieno [3,2-b:20,30-d] Pyrrole(DTP)-Based π-spacers For Efficient Dye-sensitized Solar Cells

Dye-sensitized solar cell(DSSC)offers an efficient and easily implemented technology for future energy supply.Compared to conventional silicon solar cells,it provides comparable power conversion efficiency(PCE)at low material and manufacturing costs and performs better under lower light intensities,which makes them an excellent choice for indoor applications.Up to now,such benefits have attracted considerable research interests and commercialization effort.The π-spacers of the organic dyes have a great influence on electron transfer between donors and acceptors.π-conjugated spacers containing thiophene rings have been reported showing positive effects on improving photovoltaic performances of organic sensitizers.Three D-π-A sensitizers incorporating dithieno[3,2-b:20,30-d]pyrrole(DTP)-based p-linkers were synthesized for fabricating efficient dye-sensitized solar cells(DSSCs).The DTP-based π-spacers were attached by 10-phenyl-10H-phenothiazine(JW1),5,5,10,10,15,15-hexapropyl-10,15-dihydro-5Hdiindeno[1,2-a:10,20-c]fluorene(JW2)and 4-hexyloxyphenyl(JW3).Triarylamines are mostly used as effective electron donor groups in the sensitizer molecules,which can be feasibly synthesized and modified.To reduce strong charge recombination and suppress dyes aggregation the bulky groups and alkyl chains are introduced.An additional double bond spacer was introduced between the arylamine donor and DTP-based π-spacer in the studied dyes.The conjugation of the olefin linkage enhanced π-overlapping and led to increase red shift and an extensive absorption region.The influence of different the second electron donor group located in the π-bridge on the photoelectric properties,physical properties and photochemical properties of the type of D-A-π-A organic dye-sensitized solar cells has been examined.Based on the theoretical calculation results,all of the dye molecules display good electron transport.The photovoltaic performances of solar cells based on JW1,JW2 and JW3 were measured by J–V characterizations in Co-phen based electrolyte,achieving power conversion efficiencies of 7.09%,7.87% and 6.50%,respectively.The incident photon-to-current conversion efficiency(IPCE)follows the order JW2 > JW1 > JW3,which is accordance with their photovoltaic performances.IMVS results indicate that the three dyes incorporating the modified DTP-based π-spacers have an influence on the CB shift of TiO2 and the inhibition of charge recombination.Therefore,the DTP-based π-spacer is a promising building block for developing new dyes to build highly efficient DSSCs.