Year of Award

2016

Degree Type

Thesis

Degree Name

Master of Philosophy (MPhil)

Department

Department of Chemistry.

Principal Supervisor

Leung, Louis Man Lay

Keywords

Electric properties, Indigo, Organic semiconductors, Synthesis.

Language

English

Abstract

Two new series of organic soluble indigoids 7-7-dialkoxyindigoids (4a, 4b) and 4,4-dibromo-7,7-dialkoxyindigoids (5a, 5b) (alkoxy = n-butoxy and n-octyloxy) have been synthesized starting from the inexpensive 3-hydroxybenzaldehyde for OFET applications. The indigoids were soluble in common organic solvents such as chloroform, dichloromethane, toluene, ethyl acetate and ethers. The enhanced solubility was suggested to be a lack of intermolecular hydrogen-bonds as confirmed by single crystal X-ray diffraction analyses. It was found that intramolecular hydrogen-bonds in indigoids were crucial to the exhibition of field-effect in OFETs, while intermolecular hydrogen-bonds only caused insolubility of the indigoids. Compared to the pristine insoluble indigo (LUMO = -3.55 eV and Eg = 1.91 eV), the soluble indigoids containing electron donating alkoxy side chains at the indigoid 7 and 7 positions were shown to have LUMO decreased by -0.13 to -0.26 eV as well as a lower bandgap energy from Eg = 1.66 to 1.94 eV. A bottom-gate-top-contact OFET employing polystyrene as the dielectric layer was used to demonstrate the field-effect properties. The indigoid 4,4-dibromo-7,7-dioctyloxyindigoid (5b) was found to exhibit the highest electron mobility at 2.20 ₉ 10-5 cm2V-1s-1. In addition, 4,4-dibromo-7,7-dioctyloxyindigoids (5) can be further derivatized by organometallic catalyzed aryl-aryl coupling reactions to create functional organic electronic materials.

Comments

Principal supervisor: Doctor Leung Louis M L.;Thesis submitted to the Department of Chemistry. ; Thesis (M.Phil.)--Hong Kong Baptist University, 2016. ;

Bibliography

Includes bibliographical references (pages 137-142)

Available for download on Friday, July 28, 2017


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