Influence of donor and bridge structure in D–A–π–A indoline dyes on the photovoltaic properties of dye-sensitized solar cells employing iodine/cobalt electrolyte

Abstract

D–A–π–A indoline dyes have exhibited an especially excellent performance and are regarded as one of the most promising classes of arylamine organic sensitizers. Two new D–A–π–A indoline dyes (XS45 and XS46) with different additional donor as well as a reference D–π–A indoline dye (XS47) have been synthesized to investigate the influence of donor and bridge structure in indoline dyes on the photovoltaic properties of dye-sensitized solar cells employing iodine/cobalt electrolyte. The incorporation of bulky dipropylfluorene unit in the donor part significantly increases the light harvesting ability and notably retards the charge recombination at the titania/electrolyte interface. On the other hand, the introduction of benzothiadiazole (BTD) in spacer not only evokes a large responsive range of wavelengths into NIR region, but also decreases the molar absorption coefficients of indoline dyes. DSCs incorporating Co(II/III)tris(1,10-phenanthroline)-based redox electrolyte/iodine electrolyte and three synthesized organic dyes as photosensitizers are described. The results confirm that using D–A–π–A indoline dyes as sensitizers for cobalt cells is feasible.