Understanding why replacing I3–/I– by cobalt(II)/(III) electrolytes in bis(diimine)copper(I)-based dye-sensitized solar cells improves performance

Fürer, Sebastian O. and Bozic-Weber, Biljana and Schefer, Thomas and Wobill, Cedric and Constable, Edwin C. and Housecroft, Catherine E. and Willgert, Markus. (2016) Understanding why replacing I3–/I– by cobalt(II)/(III) electrolytes in bis(diimine)copper(I)-based dye-sensitized solar cells improves performance. Journal of Materials Chemistry A, 4 (3). pp. 12995-13004.

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The performances of dye-sensitized solar cells (DSCs) comprising heteroleptic bis(diimine)copper( I ) based dyes combined with either [Co(bpy) 3 ] 2+/3+ , [Co(phen) 3 ] 2+/3+ or I 3 /I redox mediators (bpy 1/4 2,2 0 - bipyridine, phen 1/4 1,10-phenanthroline) have been evaluated. The copper( I ) dyes contain the anchoring ligand ((6,6 0 -dimethyl-[2,2 0 -bipyridine]-4,4 0 -diyl)bis(4,1-phenylene))bis(phosphonic acid), 1, and an ancillary ligand (2, 3 or 4) with a 2,9-dimethyl-1,10-phenanthroline metal-binding domain. Ligands 2 and 3 include imidazole 2 0 -functionalities with 4-(diphenylamino)phenyl (2) or 4-(bis(4-n-butoxy) phenylamino)phenyl (3) domains; in 4, the phen unit is substituted in the 4,7-positions with holetransporting 4-(diphenylamino)phenyl groups. The photoconversion efficiency, h, of each of [Cu(1)(2)] + , [Cu(1)(3)] + and [Cu(1)(4)] + considerably improves by replacing the I 3 /I electrolyte by [Co(bpy) 3 ] 2+/3+ or [Co(phen) 3 ] 2+/3+ , and after a change of electrolyte solvent (MeCN to 3-methoxypropionitrile). Due to the faster charge transfer kinetics and more positive redox potential, the cobalt-based electrolytes are superior to the I 3 /I electrolyte in terms of open-circuit voltage (V OC ), short-circuit current (J SC ) and h; values of V OC 1/4 594 mV, J SC 1/4 9.58 mA cm 2 and h 1/4 3.69% (relative to h 1/4 7.12% for N719) are achieved for the best performing DSC which contains [Cu(1)(4)] + and [Co(bpy) 3 ] 2+/3+ . Corresponding values for [Cu(1)(4)] + and I 3 /I DSCs are 570–580 mV, 5.98–6.37 mA cm 2 and 2.43–2.62%. Electrochemical impedance spectroscopy (EIS) has been used to study DSCs with [Cu(1)(4)] + and the three electrolytes. EIS shows that the DSC with I 3 /I has the highest recombination resistance, whereas the [Co(phen) 3 ] 2+/3+ electrolyte gives the highest chemical capacitance and V OC and, between [Co(bpy) 3 ] 2+/3+ and [Co(phen) 3 ] 2+/3+ , the higher recombination resistance. The [Co(phen) 3 ] 2+/3+ electrolyte exhibits the highest mass transport restrictions which result in a lower J SC and DSC efficiency compared to the [Co(bpy) 3 ] 2+/3+ electrolyte.
Faculties and Departments:05 Faculty of Science > Departement Chemie > Former Organization Units Chemistry > Anorganische Chemie (Constable)
UniBasel Contributors:Housecroft, Catherine Elizabeth and Willgert, Markus and Bozic Weber, Biljana and Wobill, Cedric and Fürer, Sebastian and Schefer, Thomas
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:Royal Society of Chemistry
Note:Publication type according to Uni Basel Research Database: Journal article
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Last Modified:29 Nov 2016 15:13
Deposited On:18 Aug 2016 09:23

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