Design, Synthesis And Characterization Of Organic Semiconductors Modified By Thiophene

This thesis focuses on the design, synthesis and characterization of thiophene-containedπconjugated organic semiconductors. The optical, electrochemical, thermal, single-crystal and devices properties of the newly synthesized materials were studied to explore their potential applications in organic electronics. The thesis consists of the following five chapters:First, the developments of organic semiconductors is reviewed, including structures of reported organic semiconducting materials and their device performances.In chapter 2, the pentacene derivatives and anthradithiophene derivatives modified by thienyl groups were designed and synthesized. The solubility, optical, electrochemical, thermal and single-crystal properties of these new materials were characterized. The relationships between their structure and property were investigated. The photooxidative stability of the new materials was improved by introducing different thienyl groups at the 6,13 positions of pentacene or 5,11 positions of the anthradithiophenes. Attaching alkyl groups in the backbone not only imparted solubility but also enhancedπ-stacking in the solid state. The new materials may have applications in optoelectronics.In chapter 3, a series of new organic semiconductors based on s-indaceno [1,2-b:5,6-b'] dithiophene-4,9-dione were successfully synthesized and characterized. We investigated the effects of systematic structural variation on their spectroscopic, electrochemical, thermal properties. The liquid crystalline phase, molecular packing in single crystals and OFET properties of selected molecules were studied. The new materials show good photooxidative stability and are soluble in common organic solvents. With n-hexyl groups attached to the framework, the new materials show p-type semiconductor properties. When the substrate temperature (TSUb) was 80℃, the OFET deivces give a hole mobility of 9.3×10-3 cm2/Vs, and on/off ratio of 4×106. The OFET devices are stable in ambient conditions for 30 days.In chapter 4, a series of new butterfly-shaped seven-ring-fused organic semiconductor was designed and synthesized. The new framework was functionalized by different alkyl substituents at a position of the terminal thienyl group. A simple oxidative cyclization reaction using FeCl3 was used to effectively construct the seven-ring-fused backbone. The new materials shew good solubility, high thermal, photooxidative stability and strong fluorescence in solution and solid state, which may be used as new fluorescent materials. X-ray crystallography results reveal that the molecule shows a unique butter-fly shape in the single crystal.In chapter 5, two series ofπconjugated organic semiconductors containing carbonyl groups were designed and synthesized. The electron withdrawing carbonyl groups lowen the LUMO energy levels, leading to increased electronegativities, which is beneficial for high photo-stability in air and electron transport, which may give get n-type semiconducting properties.