Novel Ru-based sunlight harvesters bearing dithienylpyrrolo (DTP)-bipyridine ligands: Synthesis, characterization and photovoltaic properties

• New Ru-dyes bearing dithienypyrrole moieties (DTP) have been prepared.
• They have been studied using transient spectroscopy and ab initio computations.
• Excellent light harvesting in the 350–600 nm range was observed on TiO2.
• Evidence was made of photoexcited electron capture by DTP moiety.

Bipyridine bearing π-delocalized dithienypyrrole moieties (DTP) have been involved as ligands (L) in the preparation of RuL2(dcbpy)2+ and RuL(dcbpy)(NCS)2 dyes. These dyes exhibited wide absorption domains in solution and when adsorbed on TiO2 photoanodes, light harvesting was found to be excellent (absorbance>1 in the 350–600 nm range). Careful investigations, combining transient spectroscopy and ab initio computations evidenced the capture of the photoexcited electron by low lying orbitals centred on the DTP moiety thus limiting the efficiency in DSSC despite favourable redox potentials for both injection and ground state regeneration.

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