Issue 45, 2024

Impact of water solvation on the charge carrier dynamics of organic heterojunction photocatalyst nanoparticle dispersions

Abstract

Organic heterojunction nanoparticles (NP) have recently gained significant interest as photocatalysts for visible light-driven hydrogen production. Whilst promising photocatalytic efficiencies have been reported for aqueous NP dispersions, the underlying dynamics of photogenerated charges in such organic heterojunction photocatalysts and how these might differ from more widely studied dry heterojunction films remain relatively unexplored. In this study, we combine transient optical spectroscopies over twelve orders of magnitude in time, using pulsed and continuous light illumination, to elucidate the differences in the charge carrier dynamics of heterojunction NP dispersions, dried NP films, and bulk heterojunction films prepared by spin coating. The ultrafast fast (ps to ns) transient absorption results show efficient charge generation and indistinguishable nanosecond charge recombination decay kinetics of separated charges in all three samples. In contrast, on the slower μs to ms time range, the decay kinetics of heterojunction NP dispersion exhibited up to 15-fold larger amplitude and more than one order of magnitude slower decay of the photogenerated charges than those in films. The analysis of the nanomorphology, NP surfactant, polymer residual metal content and local polar environment suggest that the longer lifetime differences (in ms) in the charge recombination in NP dispersion are mostly associated with a charge carrier stabilisation on a shallow density of states on the NP surface of ∼350 meV by interaction with local water environment, resulting in suppressed charge recombination. The lengthening of NP dispersion charge carrier lifetime is discussed regarding the energetic loss for function and their implications in photocatalysis.

Graphical abstract: Impact of water solvation on the charge carrier dynamics of organic heterojunction photocatalyst nanoparticle dispersions

Supplementary files

Article information

Article type
Edge Article
Submitted
19 Jun 2024
Accepted
20 Oct 2024
First published
21 Oct 2024
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2024,15, 19044-19056

Impact of water solvation on the charge carrier dynamics of organic heterojunction photocatalyst nanoparticle dispersions

S. Gonzalez-Carrero, J. Kosco, T. Fei, I. McCulloch and J. R. Durrant, Chem. Sci., 2024, 15, 19044 DOI: 10.1039/D4SC04030A

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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