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

Soranyel Gonzalez-Carrero Orcid Logo, Jan Kosco, Teng Fei, Iain McCulloch Orcid Logo, James Durrant Orcid Logo

Chemical Science

Swansea University Author: James Durrant Orcid Logo

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DOI (Published version): 10.1039/d4sc04030a

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 or...

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Published in: Chemical Science
ISSN: 2041-6520 2041-6539
Published: Royal Society of Chemistry 2024
Online Access: Check full text

URI: https://cronfa.swan.ac.uk/Record/cronfa68082
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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.
College: Faculty of Science and Engineering
Funders: We acknowledge financial support from the EPSRC project ATIP (EP/TO28513/1), KAUST (OSR-2018-CRG7-3749.2), from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement no. 886664, and Generalitat de Valencia (CIDEIG/2023/17) (S. G.-C.). IM acknowledges financial support from KAUST Office of Sponsored Research CRG10, by EU Horizon2020 grant agreement no. 952911, BOOSTER, grant agreement no. 862474, RoLA-FLEX, and grant agreement no. 101007084 CITYSOLAR, as well as EPSRC Projects EP/T026219/1, EP/W017091/1, and EP/L011972/1.

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