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Backbone-driven host-dopant miscibility modulates molecular doping in NDI conjugated polymers

Villalva, DR; Singh, S; Galuska, LA; Sharma, A; Han, J; Liu, J; Haque, MA; ... Baran, D; + view all (2022) Backbone-driven host-dopant miscibility modulates molecular doping in NDI conjugated polymers. Materials Horizons , 9 pp. 500-508. 10.1039/d1mh01357b. Green open access

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Abstract

Molecular doping is the key to enabling organic electronic devices, however, the design strategies to maximize doping efficiency demands further clarity and comprehension. Previous reports focus on the effect of the side chains, but the role of the backbone is still not well understood. In this study, we synthesize a series of NDI-based copolymers with bithiophene, vinylene, and acetylenic moieties (P1G, P2G, and P3G, respectively), all containing branched triethylene glycol side chains. Using computational and experimental methods, we explore the impact of the conjugated backbone using three key parameters for doping in organic semiconductors: energy levels, microstructure, and miscibility. Our experimental results show that P1G undergoes the most efficient n-type doping owed primarily to its higher dipole moment, and better host–dopant miscibility with N-DMBI. In contrast, P2G and P3G possess more planar backbones than P1G, but the lack of long-range order, and poor host–dopant miscibility limit their doping efficiency. Our data suggest that backbone planarity alone is not enough to maximize the electrical conductivity (σ) of n-type doped organic semiconductors, and that backbone polarity also plays an important role in enhancing σ via host–dopant miscibility. Finally, the thermoelectric properties of doped P1G exhibit a power factor of 0.077 μW m−1 K−2, and ultra-low in-plane thermal conductivity of 0.13 W m−1K−1 at 5 mol% of N-DMBI, which is among the lowest thermal conductivity values reported for n-type doped conjugated polymers.

Type: Article
Title: Backbone-driven host-dopant miscibility modulates molecular doping in NDI conjugated polymers
Open access status: An open access version is available from UCL Discovery
DOI: 10.1039/d1mh01357b
Publisher version: https://doi.org/10.1039/D1MH01357B
Language: English
Additional information: This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence.
Keywords: ORGANIC SEMICONDUCTORS, EFFICIENCY
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
URI: https://discovery.ucl.ac.uk/id/eprint/10141186
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