Red-Light-Mediated Photocatalytic Hydrogen Evolution by Hole Transfer from Non-Fullerene Acceptor Y6

Abstract

We report the use of blend nanoparticles (NPs) of the organic semiconductors PM6 and Y6 for the photocatalytic production of hydrogen under sacrificial conditions, with a 2% mass loading of Pt cocatalyst. When prepared using TEBS, a thiophene-containing surfactant, these blend NPs have a desirable intermixed morphology. Under ≈1-sun illumination from 400 to 900 nm, hydrogen is produced at a rate of 8000 ± 400 μmol h–1 g–1. Remarkably, this rate remains high at 5200 ± 300 μmol h–1 g–1 under 650 to 900 nm excitation, where Y6 is exclusively excited, generating free charges by hole transfer from Y6 to PM6. The rate drops to 2400 ± 200 μmol h–1 g–1 under 400 to 600 nm excitation, where PM6 is preferentially excited and free charges are generated through electron transfer. We also show that the external quantum efficiency is wavelength-independent. This work is the first study to show that free charge generation through hole transfer contributes significantly to hydrogen evolution in a donor:acceptor blend.

Surfactant Effects on Hydrogen Evolution by Small-Molecule Nonfullerene Acceptor Nanoparticles

“…This rate is ∼1.5 times lower than the rate reported by Kosco et al for TEBS-stabilized Y6 NPs . A lower rate is expected here as a lower Pt loading was used in this work (2% compared to 10%) for better comparison to other systems with Pt cocatalysts. ,, NPs stabilized with TEBS achieved an EQE of 0.054 ± 0.001% under 780 nm illumination (Figure b,c). In contrast to TEBS-stabilized Y6 NPs, Y6 NPs stabilized with SDS had a significantly lower H 2 evolution rate of 110 ± 20 μmol h –1 g –1 .…”

“…The rate of H 2 evolution and EQE exhibited by the TEBS-stabilized Y6 NPs is significantly lower than that of organic donor:NFA systems. , Optimized TEBS-stabilized PM6:Y6 NPs have been shown to achieve an EQE of 5% at 800 nm . A more direct comparison under similar experimental conditions (identical light source, reactor, Pt loading and mass of Y6) found that TEBS-stabilized 1:1 PM6:Y6 NPs have an EQE of 0.22% at 780 nm, corresponding to an approximately 4-fold increase in EQE compared to neat TEBS-stabilized Y6 NPs . This decrease in performance for a single-component system is expected due to the loss of the bulk heterojunction structure, which provides a driving force for the separation of electrons and holes.…”

“…In comparison, the NP spectra in Figure have a lower relative amplitude of the 820 nm peak, likely due to the difference in preparation method. As prepared, the NPs are colloidally stable for a period of multiple months, and Y6 NPs have previously been shown to be highly photostable under 405 nm light …”

“… Hence, Y6 NPs have significant potential for photocatalytic H 2 evolution. Indeed, Y6 NPs formed by the miniemulsion method using TEBS have been shown to evolve H 2 under sacrificial conditions. , In itself, this observation is somewhat unusual, as high photocatalytic performance from single-component small-molecule organic NPs is rarely demonstrated.…”

Sub-4 nm mapping of donor–acceptor organic semiconductor nanoparticle composition

“…In this alternate application, the nanoparticles can be used in water-based colloidal form, meaning the additional fabrication step of coating the nanoparticles to form a thin solid film is not necessary. 14 Non-fullerene acceptors (NFAs) have overtaken fullerene acceptors in organic photovoltaics and photocatalysis, [15][16][17][18][19] both BHJ and nanoparticulate, and the ability to map the morphology accurately is required for optimising structure-function relationships in device applications. In this report, we selected to study the new high performance donor-acceptor material systems PTzBI-Si:N2200 and PTQ10:IDIC, and the more well-known long-standing system TQ1:PC 71 BM, a fullerene containing system.…”