High Electrical Conductivity and Hole Transport in an Insightfully Engineered Columnar Liquid Crystal for Solution‐Processable Nanoelectronics

Abstract

Discotic liquid crystals (DLCs) are widely acknowledged as a class of organic semiconductors that can harmonize charge carrier mobility and device processability through supramolecular self‐assembly. In spite of circumventing such a major challenge in fabricating low‐cost charge transport layers, DLC‐based hole transport layers (HTLs) have remained elusive in modern organo‐electronics. In this work, a minimalistic design strategy is envisioned to effectuate a cyanovinylene‐integrated pyrene‐based discotic liquid crystal (PY‐DLC) with a room‐temperature columnar hexagonal mesophase and narrow bandgap for efficient semiconducting behavior. Adequately combined photophysical, electrochemical, and theoretical studies investigate the structure‐property relations, logically correlating them with efficient hole transport. With a low reorganization energy of 0.2 eV, PY‐DLC exhibits superior charge extraction ability from the contact electrodes at low values of applied voltage, achieving an electrical conductivity of 3.22 × 10−4 S m−1, the highest reported value for any pristine DLC film in a vertical charge transport device. The columnar self‐assembly, in conjunction with solution‐processable self‐healed films, results in commendably elevated values of hole mobility (≈10−3 cm2 V‐1s−1). This study provides an unprecedented constructive outlook toward the development of DLC semiconductors as practical HTLs in organic electronics.

Exploring the Ambipolar Charge Carrier Mobility, Mesomorphic, and Gel Properties in Nitrile Extended Quinoxaline and Phenanthro[a]phenazine Discotic Liquid Crystals

“…Charge carrier mobility studies have been carried out using space-charge-limited current (SCLC) technique, which is one of the most common techniques used for the supramolecular systems. − The mobility depends on the effectiveness of charge injection as well as the order of self-assembly in organic semiconductors (i.e., DLCs) . The current–voltage (I/V) characteristics of 3a and 5a are investigated by filling the compounds in the homeotropically aligned LC cells of thicknesses of 8.6 and 9.2 μm, respectively.…”