Inhibiting Charge Recombination in cis-Ru(NCS)(2) Diimine Sensitizers with Aromatic Substituents

Author(s)

Mueller, Andressa V. ^{[1, 2]} ; de Oliveira, Kleber T. ^[3] ; Meyer, Gerald J. ^[1] ; Polo, Andre S. ^[2]

Affiliation

^[1] Univ North Carolina Chapel Hill, Dept Chem, Chapel Hill, NC 27599 - USA

^[2] Univ Fed ABC UFABC, Ctr Ciencias Nat & Humanas, Ave Estados 5001, BR-09210580 Sao Paulo, SP - Brazil

^[3] Univ Fed Sao Carlos UFSCar, Dept Quim, Rodovia Washington Luis, km 235, BR-13565905 Sao Paulo, SP - Brazil

• Document type: Journal article
• Source: ACS APPLIED MATERIALS & INTERFACES; v. 11, n. 46, p. 43223-43234, NOV 20 2019.
• Web of Science Citations: 0

Abstract

A series of cis-{[}Ru(LL)(dcbH(2))(NCS)(2)] compounds, where dcbH(2) = 2,2'-bipyridine-4,4'-dicarboxylic acid and LL = 1,10-phenanthroline (Ru(phen)), 4,7-dipyrrole-1,10-phenanthroline (Ru(pyr)), 4,7-diindole-1,10-phenanthroline (Ru(ind)), or 4,7-dicarbazole-1,10-phenanthroline (Ru(cbz)), was investigated for application as sensitizers in mesoporous TiO2 dye-sensitized solar cells (DSSCs). A systematic increase in the number of rings of the aromatic substituents at the 4,7-positions of the 1,10-phenanthroline allowed tuning of the molecular size of the sensitizers and the energy stored in the excited state while maintaining the same ground-state Ru3+/2+ reduction potentials. These small structural changes had a significant influence on the rates and/or efficiencies of electron injection, back-electron transfer, recombination to oxidized mediators, lateral self-exchange electron transfer, and regeneration through iodide oxidation that were reflected in distinct photoelectrochemical performance of full operating DSSCs. The global efficiencies, open-circuit voltages, and short-circuit current densities of the DSSCs consistently followed the trend Ru(pyr) < Ru(ind) < Ru(phen) < Ru(cbz), and the most optimal performance of Ru(cbz) was ascribed to dramatically slower recombination to the oxidized redox mediators. Transient photovoltage and transient absorption experiments both revealed significantly slower recombination as the size of the aromatic substituents increased with Ru(cbz) providing the most promising behavior for application in dye sensitization. (AU)

• FAPESP's process: 18/08038-0 - Investigation of electron transfer processes for energy conversion systems based on Ru(II)/Re(I)
• Grantee: Andressa Vidal Muller
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate
• FAPESP's process: 18/00106-7 - Photocatalyzed Reactions by using porphyrins and continuous flow conditions: Arylations of heterocycles and activated olefins.
• Grantee: Kleber Thiago de Oliveira
• Support Opportunities: Regular Research Grants
• FAPESP's process: 16/24020-9 - Evaluation of processes photoassisted by Ru(II) and Re(I) polypyridyl compounds
• Grantee: Andressa Vidal Muller
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 16/21993-6 - Evaluation of Ru(II) and Re(I) polypyridyl compounds on photoactive devices
• Grantee: André Sarto Polo
• Support Opportunities: Regular Research Grants