UCL Discovery
UCL home » Library Services » Electronic resources » UCL Discovery

Intrinsic photogeneration of long-lived charges in a donor-orthogonal acceptor conjugated polymer

Shaikh, J; Congrave, DG; Forster, A; Minotto, A; Cacialli, F; Hele, TJH; Penfold, TJ; ... Clarke, TM; + view all (2021) Intrinsic photogeneration of long-lived charges in a donor-orthogonal acceptor conjugated polymer. Chemical Science 10.1039/d1sc00919b. (In press). Green open access

[thumbnail of d1sc00919b.pdf]
Preview
Text
d1sc00919b.pdf - Published Version

Download (1MB) | Preview

Abstract

Efficient charge photogeneration in conjugated polymers typically requires the presence of a second component to act as electron acceptor. Here, we report a novel low band-gap conjugated polymer with a donor/orthogonal acceptor motif: poly-2,6-(4,4-dihexadecyl-4H-cyclopenta [2,1-b:3,4-b′]dithiophene)-alt-2,6-spiro [cyclopenta[2,1-b:3,4-b′]dithiophene-4,9′-fluorene]-2′,7′-dicarbonitrile, referred to as PCPDT-sFCN. The role of the orthogonal acceptor is to spatially isolate the LUMO from the HOMO, allowing for negligible exchange energy between electrons in these orbitals and minimising the energy gap between singlet and triplet charge transfer states. We employ ultrafast and microsecond transient absorption spectroscopy to demonstrate that, even in the absence of a separate electron acceptor, PCPDT-sFCN shows efficient charge photogeneration in both pristine solution and film. This efficient charge generation is a result of an isoenergetic singlet/triplet charge transfer state equilibrium acting as a reservoir for charge carrier formation. Furthermore, clear evidence of enhanced triplet populations, which form in less than 1 ps, is observed. Using group theory, we show that this ultrafast triplet formation is due to highly efficient, quantum mechanically allowed intersystem crossing between the bright, initially photoexcited local singlet state and the triplet charge transfer state. Remarkably, the free charges that form via the charge transfer state are extraordinarily long-lived with millisecond lifetimes, possibly due to the stabilisation imparted by the spatial separation of PCPDT-sFCN's donor and orthogonal acceptor motifs. The efficient generation of long-lived charge carriers in a pristine polymer paves the way for single-material applications such as organic photovoltaics and photodetectors.

Type: Article
Title: Intrinsic photogeneration of long-lived charges in a donor-orthogonal acceptor conjugated polymer
Open access status: An open access version is available from UCL Discovery
DOI: 10.1039/d1sc00919b
Publisher version: https://doi.org/10.1039/d1sc00919b
Language: English
Additional information: This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence (http://creativecommons.org/licenses/by-nc/3.0/).
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy
URI: https://discovery.ucl.ac.uk/id/eprint/10128878
Downloads since deposit
32Downloads
Download activity - last month
Download activity - last 12 months
Downloads by country - last 12 months

Archive Staff Only

View Item View Item