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Optical gain in semiconducting polymer nano and mesoparticles

Lookup NU author(s): Professor Mark GeogheganORCiD



This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


The presence of excited-states and charge-separated species was identified through UV and visible laser pump and visible/near-infrared probe femtosecond transient absorption spectroscopy in spin coated films of poly[N-9″-heptadecanyl-2,7-carbazole-alt-5,5-(4,7-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT) nanoparticles and mesoparticles. Optical gain in the mesoparticle films is observed after excitation at both 400 and 610 nm. In the mesoparticle film, charge generation after UV excitation appears after around 50 ps, but little is observed after visible pump excitation. In the nanoparticle film, as for a uniform film of the pure polymer, charge formation was efficiently induced by UV excitation pump, while excitation of the low energetic absorption states (at 610 nm) induces in the nanoparticle film a large optical gain region reducing the charge formation efficiency. It is proposed that the different intermolecular interactions and molecular order within the nanoparticles and mesoparticles are responsible for their markedly different photophysical behavior. These results therefore demonstrate the possibility of a hitherto unexplored route to stimulated emission in a conjugated polymer that has relatively undemanding film preparation requirements.

Publication metadata

Author(s): Geoghegan M, Mróz MM, Botta C, Parrenin L, Brochon C, Cloutet E, Pavlopoulou E, Hadziioannou G, Virgili T

Publication type: Article

Publication status: Published

Journal: Molecules

Year: 2021

Volume: 26

Issue: 4

Online publication date: 20/02/2021

Acceptance date: 17/02/2021

Date deposited: 05/08/2021

ISSN (print): 1431-5165

ISSN (electronic): 1420-3049

Publisher: MDPI AG


DOI: 10.3390/molecules26041138


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