New Electrode-Friendly Triindole Columnar Phases with High Hole Mobility

In recent years, the search for low-cost electronic devices with flexible and easy to process components motivated the interest in organic electronic technology.1 Among the various classes of materials developed in such area, discotic mesophases show intriguing properties: their ability to selfassemble into columnar stacks with aromatic cores surrounded by saturated hydrocarbon peripheral chains gives rise to an insulated, coaxial structure in which onedimensional transport of charge is possible via the π-electronic conjugated systems of the molecules. This makes discotic liquid crystals particularly suitable as organic charge transport layers in many different devices, such as light emitting diodes, field effect transistors, and photovoltaic cells.2 An important transport layer property that can heavily influence a device performance is charge mobility, often a limiting factor with amorphous organics but relatively high in ordered mesophases.3 The search for mesomorphic materials with good mobility is therefore of high relevance in order to obtain devices with improved performance. The mobility of many types of discotic mesogens, with different cores (e.g., triphenylene,4 hexaazatriphenylene,5 porphyrin,6 perylene, 7 phthalocyanine,8 perihexabenzocoronene9), was characterized by using different methods, such as time-of-flight (TOF),10 pulse radiolysis-time resolved microwave conductivity (PR-TRMC),11 space charge limited current (SCLC),12 and field effect transistor (FET)13techniques, obtaining in some cases very high charge mobilities9a (even approaching the value μ ≈ 3 cm2 V-1 s-1, found for the intersheet mobility in graphite).