Novel iminocoumarin dyes as photosensitizers for dye-sensitized solar cell

Novel iminocoumarin dyes (2a–c and 3a–c) having carboxyl and hydroxyl anchoring groups onto the dyes skeletons have been designed and synthesized for the application of dye-sensitized nanocrystalline TiO2 solar cells (DSSCs). The photophysical and electrochemical studies showed that these iminocoumarin dyes are suitable as light harvesting sensitizers in DSSC application. The dyes having carboxyl and hydroxyl anchoring groups (2a–c) showed better efficiency when compared to the dyes having carboxyl group (3a–c) alone. The cell consisted of dye 2a generated the highest solar-to-electricity conversion efficiency (η) of 0.767% (open circuit voltage (Voc) = 0.491 V, short circuit photocurrent density (Jsc) = 2.461 mA cm−2, fill factor (ff) = 0.635) under simulated AM 1.5 irradiation (1000 W m−2) with a total semiconductor area of 0.25 cm2. The corresponding incident photon-to-current conversion efficiency (IPCE) of the above cell was 21.38%. The overall low efficiency of the dyes is ascribed to the lack of light harvesting ability at longer wavelength region.