Synthesis and characterization of cobalt complexes based on ß-diketiminate and polypyridyl ligands as redox shuttles for DSSCs
Felipe Vinocour a b, Leslie Pineda a b
a Centro de Investigación en Electroquímica y Energía Química, Ciudad de la Investigación Universidad de Costa Rica De Muñoz y Nanne, 700 m norte. San José Costa Rica 11501-2060, Costa Rica
b Escuela de Química, Universidad de Costa Rica, Apartado 2060, San José
International Conference on Hybrid and Organic Photovoltaics
Proceedings of 6th International Conference on Hybrid and Organic Photovoltaics (HOPV14)
Ecublens, Switzerland, 2014 May 11th - 14th
Organizers: Michael Graetzel and Mohammad Nazeeruddin
Poster, Felipe Vinocour, 243
Publication date: 1st March 2014

The quest for carbon neutral energy sources has recently focused on the great potential of solar energy;1–4 hence it has unchained a development in research and optimization of the different components of photovoltaic devices.5–10 Iodide-triiodide (I-/I3-) is currently the electrolyte system of choice in dye-sensitized solar cells (DSSCs), attributable to its conduction mechanism allowing quick regeneration of the dye, and also its complex charge transfer that translates in slow recombination kinetics and lower current dissipation; 7,8,11–13 despite the benefits there are also challenges to overcome regarding the practical incompatibility with several materials because of its corrosive character, loss of material and efficiency over time due to inherent volatility, competitive absorption of the solar radiation, and limitations in the dark current potential (VOC).14–20 In response to the I-/I3- disadvantages there has been several attempts to attain a viable alternative, one of the most successful approach falling into the field of organometallic-cobalt chemistry;21–25 following this development the objective of the present work is to synthetize and evaluate two cobalt complexes as a redox mediator for DSSCs: one tridentate ligand similar to the more traditional poly-pyridine systems, and the second one based on a β-diketiminate tetradentate ligand that introduces a six-membered chelate ring.

Both shuttles will be characterized by FT-IR, UV-Vis and NMR spectroscopy. Moreover, photoelectrochemical properties (Voc, IPCE, and Jsc) and electrochemical impedance will be measured for further comparison by theoretical calculations of shuttle redox potentials.

Development of alternative systems could open new venues for electrolyte-dye pairs with optimal energy-level pairing, improving stability and efficiencies, as demonstrated by several more positive redox potential reported in the literature.21,24,26–28

Figure 1. Scheme of general working principle of DSSCs.
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