Correlation Between Charge Recombination and Lateral Hole-Hopping Kinetics in a Series of cis-Ru(phen ')(dcb)(NCS)(2) Dye-Sensitized Solar Cells

Author(s)

Sampaio, Renato N. ; Mueller, Andressa V. ; Polo, Andre S. ; Meyer, Gerald J.

• Document type: Journal article
• Source: ACS APPLIED MATERIALS & INTERFACES; v. 9, n. 39, p. 9-pg., 2017-10-04.

Abstract

Four complexes of the general form cfs-Ru(phen')-(dcb)(NCS)(2) , where deb is 4,4'-(CO2H)(2)-2,2'-bipyridine and phen' is 1,10-phenanthroline (phen), 4,7-(C6H5 )(2)-phen (Ph-2-phen), 4,7-(CH3)(2)-phen (Me-2-phen), or 3,4,7,8-(CH3)(4)-phen (Me-4-phen), were anchored to mesoporous TiO2 thin films for applications as sensitizers in dye-sensitized solar cells (DSSCs). The compounds displayed metal based reductions E circle(Ru-m/u) = 1.01 +/- 0.05 V vs NHE and were potent reductants competent of excited-state electron transfer to TiO2 with yields phi(inj) >= 0.75 in acetonitrile electrolytes. Average charge recombination rate constants, k(cr) , abstracted from nanosecond transient absorption measurements, and the apparent diffusion coefficients for lateral hole-hopping, abstracted from chronabsorptometry measurements, showed the same sensitizer dependency: Ru(Me-4-phen) >Ru(Ph-2-phen) >Ru(Me-2-phen) approximate to Ru(phen). When used in operational solar cells, Ru(Ph-2-phen) was most optimal with an efficiency of (6.6 +/- 0.5)% in ionic liquids under 1 sun illumination. The superior performance of Ru(Ph-2-phen) was traced to a higher injection yield and more efficient regeneration due to an unusually small sensitivity of k(cr) to the number of injected electrons. (AU)

• FAPESP's process: 13/25173-5 - Photoreactivity and kinetic formation of ruthenium (II) tris-heteroleptic compounds
• Grantee: André Sarto Polo
• Support Opportunities: Regular Research Grants
• FAPESP's process: 15/00605-5 - Investigation of the formation kinetics of tris-heteroleptic Ru(II) compounds with potential application in energy conversion
• Grantee: Andressa Vidal Muller
• Support Opportunities: Scholarships in Brazil - Master