Electron and hole ambipolar transport hybrid liquid crystal dimers of C60 and triphenylene with varied length alkyl tails

Abstract

Fullerene-based liquid crystals represent a class of advanced functional materials combining the advantageous characteristics of C₆₀ and ordered soft matter liquid crystals. In this work, a series of triphenylene–fullerene hybrid liquid crystal (LC) dimers of TP_n-A12-C₆₀ with a dodecyl spacer and different length alkyl tails (n = 4–6, 8, 10, and 12) have been prepared and fully characterized. A systematic investigation demonstrated that the series of hybrid dimers developed into various hierarchical lamellar structures by virtue of competition and compromise between the fullerene units and the modified triphenylene moieties with varied length alkyl tails. The hybrid LC dimers of TP_n-A12-C₆₀ with shorter alkyl tails (n = 4, 5, and 6) formed a lamellar structure Squ/Lam with the C₆₀ units organizing into a square (Squ) superlattice; while those with longer alkyl tails (n = 8, 10, and 12) exhibited a hierarchical lamellar structure of Rec/Col_x with the triphenylene moieties forming a lower order columnar organization (Col_x) and the C₆₀ units experiencing a slight distortion into a rectangular superstructure (Rec). More importantly, the series of hybrid LC dimers in a net single component system manifest remarkable electron and hole ambipolar transport properties. For instance, TP₄-A12-C₆₀ demonstrates the highest charge carrier mobilities of 9.64 × 10⁻³ cm² V⁻¹ s⁻¹ for electrons and 8.27 × 10⁻³ cm² V⁻¹ s⁻¹ for holes, which enable it to be promising for use as a unique ambipolar transport organic optoelectronic material.