Impact of Molecular Orientation on Lateral and Interfacial Electron Transfer at Oxide Interfaces

Author(s)

Loague, Quentin ; Keller, Niklas D. ; Muller, Andressa V. ; Aramburu-Troselj, Bruno Martin ; Bangle, Rachel E. ; Schneider, Jenny ; Sampaio, Renato N. ; Polo, Andre S. ; Meyer, Gerald J.

• Document type: Journal article
• Source: ACS APPLIED MATERIALS & INTERFACES; v. 15, n. 28, p. 14-pg., 2023-07-07.

Abstract

Molecular dyes, called sensitizers, with a cis-[Ru(LL)(dcb)(NCS)(2)] structure, where dcb is 4,4 & PRIME;-(CO2H)(2)-2,2 & PRIME;-bipyridine and LL is dcb or a differentdiimine ligand, are among the most optimal for application in dye-sensitizedsolar cells (DSSCs). Herein, a series of five sensitizers, threebearing two dcb ligands and two bearing one dcb ligand, were anchoredto mesoporous thin films of conducting tin-doped indium oxide (ITO)or semiconducting TiO2 nanocrystallites. The number ofdcb ligands impacts the surface orientation of the sensitizer; densityfunctional theory (DFT) calculations revealed an & SIM;1.6 & ANGS;smaller distance between the oxide surface and the Ru metal centerfor sensitizers with two dcb ligands. Interfacial electron transferkinetics from the oxide material to the oxidized sensitizer were measuredas a function of the thermodynamic driving force. Analysis of thekinetic data with Marcus-Gerischer theory indicated that theelectron coupling matrix element, H (ab),was sensitive to distance and ranged from H (ab) = 0.23 to 0.70 cm(-1), indicative of nonadiabaticelectron transfer. The reorganization energies, & lambda;, were alsosensitive to the sensitizer location within the electric double layerand were smaller, with one exception, for sensitizers bearing twodcb ligands & lambda; = 0.40-0.55 eV relative to those with one & lambda; = 0.63-0.66 eV, in agreement with dielectric continuumtheory. Electron transfer from the oxide to the photoexcited sensitizerwas observed when the diimine ligand was more easily reduced thanthe dcb ligand. Lateral self-exchange "hole hopping"electron transfer between surface-anchored sensitizers was found tobe absent for sensitizers with two dcb ligands, while those with onlyone were found to hop with rates similar to those previously reportedin the literature, k (hh) = 47-89 & mu;s(-1). Collectively, the kinetic data and analysisreveal that interfacial kinetics are highly sensitive to the surfaceorientation and sensitizers bearing two dcb ligands are most optimalfor practical applications of DSSCs. (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: 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: 22/07268-8 - Comprehending the charge recombination processes in perovskite solar cells
• Grantee: André Sarto Polo
• Support Opportunities: Regular Research Grants
• FAPESP's process: 19/23277-4 - Investigation on electron transfer processes in photoactive devices
• Grantee: André Sarto Polo
• Support Opportunities: Regular Research Grants