Constructing highly planar, extended π-electron systems is an important strategy for achieving high-mobility organic semiconductors. In general, there are two synthetic strategies for achieving π-conjugated systems with high planarity. The conventional strategy connects neighboring aromatic rings through covalent bonds to restrict the rotation about single bonds. However, this usually requires a complex sequence of synthetic steps to achieve this target, which can be costly and labor-intensive. More recently, noncovalent through-space intramolecular interactions, which are defined here as noncovalent conformational locks, have been employed with great success to increase the planarity and rigidity of extended π-electron systems; this has become a well-known and important strategy to design and synthesize highly planar π-conjugated systems for organic electronics. This review offers a comprehensive and general summary of conjugated systems with such noncovalent conformational locks, including O···S, N···S, X···S (where X = Cl, Br, F), and H···S through-space interactions, together with analysis by density functional theory computation, X-ray diffraction, and microstructural characterization, as well as by evaluation of charge transport in organic thin-film transistors and solar cells.
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