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The effect of the dielectric environment on electron transfer reactions at the interfaces of molecular sensitized semiconductors in electrolytes

Title: The effect of the dielectric environment on electron transfer reactions at the interfaces of molecular sensitized semiconductors in electrolytes
Authors: Moia, D
Abe, M
Wagner, P
Saguchi, H
Koumura, N
Nelson, J
Barnes, PRF
Mori, S
Item Type: Journal Article
Abstract: Electron transfer theories predict that rates of charge transfer vary with the dielectric properties of the environment where the reaction occurs. An appropriate description of this relation for molecular sensitized semiconductors in electrolytes must account for the restricted geometry of these systems compared to “free” molecules in solution. Here, we explore the extent to which dielectric properties of the surrounding medium can explain the rates of charge transfer processes, measured using transient absorption spectroscopy, involving photo-oxidized thiophene–carbazole-based molecules on oxide semiconductors in inert or redox-active electrolytes. We observe no clear correlation between the activation energy of hole hopping between molecules on oxide surfaces or the recombination rate between photogenerated electrons in the oxide and holes on the adsorbed molecules and the dielectric properties of the surrounding solvent. The activation energy of hole hopping tends to increase with time following initial photogeneration of the holes, which we attribute to energetic disorder in the molecular monolayer. The recombination rate in different solvents scales with the hole hopping rate. It can also be varied by adding inert salts in the electrolyte and by controlling the access of cations in solution to the oxide surface. Finally, we show that fast electron transfer from cobalt complexes to photo-oxidized molecules in solvents with low polarity is verified, but the kinetics are limited by the ionic dissociation. Our study highlights the importance of electronic coupling between the redox-active components and their solvation, besides the reorganization energy and the driving force, in the determination of electron transfer rates at molecular sensitized interfaces in electrolytes.
Issue Date: 2-Apr-2020
Date of Acceptance: 6-Mar-2020
URI: http://hdl.handle.net/10044/1/82021
DOI: 10.1021/acs.jpcc.9b11860
ISSN: 1932-7447
Publisher: American Chemical Society
Start Page: 6979
End Page: 6992
Journal / Book Title: The Journal of Physical Chemistry C: Energy Conversion and Storage, Optical and Electronic Devices, Interfaces, Nanomaterials, and Hard Matter
Volume: 124
Issue: 13
Copyright Statement: © 2020 American Chemical Society.
Keywords: Science & Technology
Physical Sciences
Technology
Chemistry, Physical
Nanoscience & Nanotechnology
Materials Science, Multidisciplinary
Chemistry
Science & Technology - Other Topics
Materials Science
NANOCRYSTALLINE TIO2 FILMS
DYE REGENERATION KINETICS
LATERAL SELF-EXCHANGE
SOLAR-CELLS
REORGANIZATION ENERGY
CHARGE RECOMBINATION
SOLID-STATE
HOLE TRANSPORT
ORGANIC-DYES
DEPENDENCE
Science & Technology
Physical Sciences
Technology
Chemistry, Physical
Nanoscience & Nanotechnology
Materials Science, Multidisciplinary
Chemistry
Science & Technology - Other Topics
Materials Science
NANOCRYSTALLINE TIO2 FILMS
DYE REGENERATION KINETICS
LATERAL SELF-EXCHANGE
SOLAR-CELLS
REORGANIZATION ENERGY
CHARGE RECOMBINATION
SOLID-STATE
HOLE TRANSPORT
ORGANIC-DYES
DEPENDENCE
03 Chemical Sciences
09 Engineering
10 Technology
Physical Chemistry
Publication Status: Published
Online Publication Date: 2020-03-19
Appears in Collections:Physics
Experimental Solid State
Grantham Institute for Climate Change
Faculty of Natural Sciences