Optoelectronic properties of ambipolar transport triphenylene-perylene donor–acceptor discotic liquid crystals

Abstract

A series of novel discotic liquid-crystalline donor–acceptor (D–A) dyads 5D10An (n = 4, 5, 6, 7, 8) adjusted by changing the chain length (n) of diester groups on perylene were synthesized based on triphenylene and perylene units, which were linked by a flexible linkage of 10-decyloxy-1-amine. Results from differential scanning calorimetry (DSC), one-dimensional X-ray diffraction (XRD) patterns, and polarized optical microscopy (POM) images indicate that 5D10A4, 5D10A5, 5D10A6, and 5D10A7 exhibited hexagonal columnar phase at high temperature ranges and rectangular columnar phases at room temperature. Combining the XRD data and the steady state spectra of UV-Vis and fluorescence spectroscopy, the intramolecular triphenylenes and perylene diester cores were stacked separately in distinct columns and nano-segregation occurred during self-assembly. The HOMO/LUMO energy levels were obtained using CV, UV-Vis spectroscopy, UPS and Gaussian09. Charge carrier mobilities were measured by a time-of-flight (TOF) device. These discotic liquid-crystalline compounds exhibited highly efficient ambipolar charge-transport properties, and the hole and electron mobilities can reach the order of 10⁻³ cm² V⁻¹ s⁻¹ by segregated D–A columns. This is the first report on D–A dyads’ discotic liquid crystals, which not only feature ambipolar transport but also exhibit columnar phase structures that can be stabilized at room temperature, providing potential utility of the strategy in organic optoelectronic applications.