Publications by authors named "Calvyn T Howells"

Organic semiconductor nanoparticles (NPs) composed of an electron donor/acceptor (D/A) semiconductor blend have recently emerged as an efficient class of hydrogen-evolution photocatalysts. It is demonstrated that using conjugated polymers functionalized with (oligo)ethylene glycol side chains in NP photocatalysts can greatly enhance their H -evolution efficiency compared to their nonglycolated analogues. The strategy is broadly applicable to a range of structurally diverse conjugated polymers.

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Article Synopsis
  • Incorporating a heterojunction between a donor polymer (PTB7-Th) and a non-fullerene acceptor (EH-IDTBR) in organic nanoparticles enhances photocatalytic activity for hydrogen evolution compared to single organic semiconductors.
  • Adjusting the stabilizing surfactant during nanoparticle fabrication allows for control over the nanomorphology, transforming the structure from core-shell to intermixed blend, and significantly increases hydrogen production efficiency.
  • The optimized photocatalysts achieve an impressive hydrogen evolution rate of over 60,000 µmol h g under visible light (350 to 800 nm), with external quantum efficiencies exceeding 6% at peak solar photon flux.
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Two novel triads based on a diketopyrrolopyrrole (DPP) central core and two 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) units attached by thiophene rings have been synthesised having high molar extinction coefficients. These triads were characterised and used as donor materials in small molecule, solution processable organic solar cells. Both triads were blended with PC71BM as an acceptor in different ratios by wt % and their photovoltaic properties were studied.

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The morphology of bulk heterojunction organic photovoltaic cells controls many of the performance characteristics of devices. However, measuring this morphology is challenging because of the small length-scales and low contrast between organic materials. Here we use nanoscale photocurrent mapping, ultrafast fluorescence and exciton diffusion to observe the detailed morphology of a high-performance blend of PTB7:PC71BM.

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