Exceptionally high charge mobility in phthalocyanine-based poly(benzimidazobenzophenanthroline)-ladder-type two-dimensional conjugated polymers

June 19, 2023

Finding potential organic alternatives to traditional silicon-based semiconductors has been a long-standing goal in the field of organic chemistry. A work recently published in ‘Nature Materials’ reports highly conjugated two-dimensional conjugated polymers with exceptionally high short-range charge mobility of approaching cm2V-1s-1 at room temperature.

Two-dimensional conjugated polymers (2D CPs), consisting of multi-strands of linear CPs with extended in-plane π-conjugation, are emerging crystalline semiconducting polymers for organic (opto-)electronics. However, state-of-the-art 2D CPs typically exhibit limited charge transport properties due to poor p-conjugation.

Now, a team of researchers from Technische Universität Dresden, Max Planck Institute for Polymer Research, University of Sofia, Max Planck Institute of Microstructure Physics, Chinese Academy of Sciences, University of Mons, Friedrich-Alexander-Universität Erlangen-Nürnberg, Instituto Madrileño de Estudios Avanzados en Nanociencia, and Shandong University, overcomes this limitation in a study recently published in Nature Materials. Guided by theoretical computations of representative model compounds forming various conjugated linkages, they demonstrated optimal p-conjugation in poly(benzimidazobenzophenanthroline) (BBL)-ladder-type crystalline 2D CPs (termed as 2DCP-MPc, with M = Cu or Ni). Synthesized from octaaminophthalocyaninato metal(II) and naphthalenetetracarboxylic dianhydride via acid-modulated polycondensation under solvothermal conditions, 2DCP-MPcs exhibit a narrow HOMO-LUMO  gap of ~1.3 eV and strongly dispersive energy bands with small electronhole reduced effective masses of ~0.15 m0. The strong p-conjugation allows band transport in 2DCP-MPcs with an exceptionally high short-range sum mobility of electrons and holes approaching 1000 cm2V-1s-1 at room temperature, significantly exceeding linear and 2D CPs. These properties make 2DCP-MPcs shine possess great potential for high-mobility organic electronics.

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