New D–π–A dyes incorporating dithieno[3,2-b:2′,3′-d]pyrrole (DTP)-based π-spacers for efficient dye-sensitized solar cells

Abstract

Three D–π–A sensitizers incorporating dithieno[3,2-b:2′,3′-d]pyrrole (DTP)-based π-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-5H-diindeno[1,2-a:1′,2′-c]fluorene (JW2) and 4-hexyloxyphenyl (JW3). The bulky groups and alkyl chains are introduced to suppress dye aggregation as well as reduce electron recombination. An additional double bond spacer was introduced between the arylamine donor and DTP-based π-spacer in the studied dyes. Based on the theoretical calculation results, all of the dye molecules display good electron transport. The photovoltaic performances of device 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.