RATIONAL DESIGN AND SYNTHESIS OF DISCOTIC LIQUID CRYSTALS FOR ORGANIC ELECTRONICS APPLICATIONS

Abstract

Organic semiconductors (OSCs) have gained tremendous attention in both industries and academia, with potential emerging applications in molecular electronics to solve the increasing global energy crisis. The main challenge is finding organic compounds that can form defect free uniform thin films. In this regard, discotic liquid crystals (DLCs) composed of a central π conjugated rigid aromatic core and flexible alkyl chains at the periphery ease the fabrication procedure by solution processing method.1 Better-performing OSCs necessitate optimized essential parameters such as high charge (hole or electron) mobility, electronic structure, solution processability, and thermal stability. The objective of the Ph.D. thesis is to rationally design, synthesize, and characterize room temperature DLC materials that exhibit favorable self-organization, imparting increased molecular stacking for efficient charge transport. Several known DLCs have electron-rich cores, but few electron-deficient systems have been found. In this regard, an electron-deficient DLC has been rationally designed and synthesized using a tris(triazole) nitrogen-rich core, demonstrating fast electron transport.2 DLCs for hole-transporting materials have also been developed and showed increased hole mobility with increasing temperature, which can potentially be applied in nonlinear organic electronics.3 Through meticulous design strategy selection, columnar self-assembly and luminescence can be combined to significantly aid in developing new DLC-based emitters for organic light emitting diode (OLED) applications. The luminescent columnar perylene tetraester-based DLCs were developed to fabricate as emitters in solution-processable OLEDs.4 The columnar and nematic phases have been investigated as viable candidates for deep-blue emissive layers in OLEDs, leading to low driving voltage and improved device efficiencies