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Issue 30, 2016
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Tuning charge transport from unipolar (n-type) to ambipolar in bis(naphthalene diimide) derivatives by introducing π-conjugated heterocyclic bridging moieties

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Abstract

A series of acceptor–donor–acceptor (A–D–A) conjugated molecules based on naphthalene diimide dimers bridged with different π-conjugated heterocyclic units (NDI–π–NDI) have been designed and synthesized. By an ingenious design strategy, the LUMO (the lowest unoccupied molecular orbital) of the NDI-based small molecules is well controlled to a relatively constant value of −3.8 to −3.9 eV, whereas their HOMO (the highest occupied molecular orbital) could be tuned over a wide range, from −6.5 eV (compound 1) to −5.5 eV (compound 5), leading to varied band gaps from 2.6 eV to 1.5 eV. Organic field-effect transistor (OFET) characterization of these NDI–π–NDI molecules shows that compounds 1, 2, and 3 have good n-type semiconducting properties in a N2 atmosphere with the maximum electron mobilities up to 0.15 cm2 V−1 s−1, 0.46 cm2 V−1 s−1 and 0.57 cm2 V−1 s−1, respectively. Compounds 4 and 5, due to the high-lying HOMO levels and reduced energy band gaps, have ambipolar semiconducting properties and OFETs based on 5 show the highest electron and hole mobilities up to 1.23 cm2 V−1 s−1 and 0.0074 cm2 V−1 s−1, respectively. Moreover, the performances are enhanced under thermal treatment because of the increased crystallinity as evidenced by X-ray diffraction (XRD) and atomic force microscopy (AFM). The easily tunable electronic energy levels make the NDI-based semiconductors promising n-channel and ambipolar components in organic devices.

Graphical abstract: Tuning charge transport from unipolar (n-type) to ambipolar in bis(naphthalene diimide) derivatives by introducing π-conjugated heterocyclic bridging moieties

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Publication details

The article was received on 01 May 2016, accepted on 22 Jun 2016 and first published on 23 Jun 2016


Article type: Paper
DOI: 10.1039/C6TC01769J
Citation: J. Mater. Chem. C, 2016,4, 7230-7240
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    Tuning charge transport from unipolar (n-type) to ambipolar in bis(naphthalene diimide) derivatives by introducing π-conjugated heterocyclic bridging moieties

    Z. Wang, X. Li, Y. Zou, J. Tan, X. Fu, J. Liu, C. Xiao, H. Dong, W. Jiang, F. Liu, Y. Zhen, Z. Wang, T. P. Russell and W. Hu, J. Mater. Chem. C, 2016, 4, 7230
    DOI: 10.1039/C6TC01769J

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