Highly‐Active Chiral Organic Photovoltaic Catalysts with Suppressed Charge Recombination

Abstract

Recombination of free charges in organic semiconductors reduces the available photo‐induced charge‐carriers and restricts photovoltaic efficiency. In this work, the chiral organic semiconductors (Y6‐R and Y6‐S with enantiopure R‐ and S‐ chiral alkyl sidechains) are designed and synthesized, which show effective aggregation‐induced chirality through mainchain packing with chiral conformations in non‐centrosymmetric space groups with tilt chirality. Based on the analysis of spin‐injection, magnetic‐hysteresis loop, and thermodynamics and dynamics of the excited state, we suggest that the aggregation‐induced chirality can generate spin‐polarization, which suppresses charge recombination and offers more available charge‐carriers within Y6‐R and Y6‐S relative to the achiral counterpart (Y6). Then the chiral Y6‐R and Y6‐S show enhanced catalytic activity with optimal average hydrogen evolution rates of 205 and 217 mmol h−1 g−1, respectively, 60–70 % higher than Y6, when they are employed as nanoparticle photocatalysts in photocatalytic hydrogen evolution under simulated solar light, AM1.5G, 100 mW cm−2.

From light to hydrogen: the complete life cycle of free charges in photocatalytic nanoparticles

“…43 However, equivalent modeling of the photophysics of neat Y6 NPs has not been reported. Y6 NPs and Y6 films have significant differences in steady-state absorption, 29–32,43 which broadly indicate a lower degree of ordering in Y6 NPs compared to Y6 films. 59 Due to this difference in molecular packing, further analysis of the photophysics of neat Y6 NPs is required to understand the extent of free charge generation in this more disordered morphology.…”

“…1b) and other members of the Y-series. 24,25 Single-component polymeric 26,27 and small-molecule 28–31 NPs as well as donor:acceptor NPs at both conventional 32–36 and unconventional 37 donor:acceptor ratios produced from materials from the organic photovoltaic field have been shown to effectively reduce protons to H 2 under excitation wavelengths across the visible and near-infrared. 38 The highest production rates are typically achieved with donor:acceptor blends, with most reports using a sacrificial electron donor such as ascorbic acid (AA).…”

“…Kosco et al reported that AA is a slow hole scavenger (10 μs timescale), 34 but systems without long-lived polarons are also active with AA. 28–31 Understanding the properties that limit or promote transfer of electrons and holes to co-catalysts and sacrificial reagents is important for the future optimization of these systems.…”

Emerging Light‐Harvesting Materials Based on Organic Photovoltaic D/A Heterojunctions for Efficient Photocatalytic Water Splitting

“…With the aim of bringing down the effect of photogenerated carrier recombination on photocatalyst efficiency, an interesting acceptor couple of Y6-R and Y6-S was developed with enantiopure R-and Schiral alkyl side chains. [31] Y6-R and Y6-S showed effective aggregation-induced chirality, which contributed to the suppressed charge recombination and better photocatalytic hydrogen yield rates relative to their achiral counterpart (Y6). For the first time, the positive effects of molecular chirality on organic photosensitizer-based photocatalytic hydrogen production were disclosed.…”

“…Hydrogen yield rate (mmol h À 1 g À 1 ) Surfactants [a] PTB7-Th/EH-IDTBR [18] 5 wt % Pt 64.4 TEBS PTB7-Th/EH-IDTBR [18] 5 wt % Pt 3.1 SDS PCDTBT/PC 60 BM [20] 3 wt % Pt 105.2 / PFBT/PFODTBT/ITIC [22] 6 wt % Pt 60.8 PS-PEG-COOH PM6/ITCC-M [23] 10 wt % Pt 260 SDBS PM6/ITCC-M/IDMIC-4F [23] 10 wt % Pt 306 SDBS gIDTBT/oIDTBR [24] 10 wt % Pt 18.5 TEBS PM6/Y6 [25] 10 wt % Pt 43.9 TEBS PM6/PC 71 BM [25] 5 wt % Pt 73.7 TEBS PM6/BTP-4F [26] 15 wt % Pt 64.3 TEBS PM6/BTP-FOH [26] 15 wt % Pt 78.4 TEBS PM6/BTP-2OH [26] 15 wt % Pt 102.1 TEBS PM6/TPP [27] 20 wt % Pt 72.7 TEBS F1 [28] 33 wt % Pt 152.6 TEBS PM6/Y6CO [30] 33 wt % Pt 323.2 TEBS PM6/Y6-R [31] 16 wt % Pt 205 TEBS PM6/Y6-S [31] 16 wt % Pt 217 TEBS PBDB-T/ITIC [32] 10 wt % Pt 257 SDBS POZ-M/ITIC [33] 6 wt % Pt 63 PS-PEG-COOH…”