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

D-A-pi-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-pi-A indoline dyes (XS45 and XS46) with different additional donor as well as a reference D-A-pi-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-pi-A indoline dyes as sensitizers for cobalt cells is feasible. (C) 2013 Elsevier Ltd. All rights reserved.