A new cobalt-terpyridine redox shuttle (Co(Cl-phenyl-terpyridine)(2)) has been synthesized, characterized, computationally investigated and then tested in photovoltaic devices, in conjunction with the prototypical N719 and Z907 ruthenium dyes. Lower efficiencies compared to the reference Co(bpy)(3) redox couple were obtained, probably due to increased recombination processes. Improvements in the devices performances were obtained by using chenodeoxycholic acid as surface co-adsorbent and as an electrolyte additive. Moreover, to better rationalize the photovoltaic results, the effect of two different counterions (TFSI and PF6) has been investigated for the reference Co(bpy)(3) electrolyte, finding a reduced efficiency for the TFSI-based electrolyte. (C) 2013 Elsevier B.V. All rights reserved.