Authors:	Li, Mengmeng
Title:	Molecular self-assembly in mono- to multilayer organic field-effect transistors
Online publication date:	13-May-2016
Year of first publication:	2016
Language:	english
Abstract:	Organic semiconductors hold a great potential in applications of low-cost, light-weight, large-area and flexible electronic devices. In the present thesis, the precise control of microstructure and molecular ordering of organic semiconducting mono- to multilayers is realized by various processing techniques, especially solution processing. First, the intrinsic role of interfacial microstructure on the charge carrier transport is investigated by using the dielectrics with the surface roughness on a sub-nanometer scale. Such dielectrics allow the fine control of the microstructure of only the interfacial semiconducting layer. Three different semiconductor systems, including semicrystalline and amorphous polymers as well as crystalline small molecule, are processed from solution, and it is demonstrated that the interfacial microstructure has basically no impact on the charge carrier transport in multilayers. Second, a single molecular layer of a conjugated polymer is fabricated by dip-coating, with the thickness of 2.4 nm. This polymer monolayer exhibits a high degree of molecular ordering and strong pi-stacking interactions. More importantly, the transistor based on such a polymer monolayer shows an excellent charge carrier transport, with the maximum field-effect mobility over 3 cm2 V-1 s-1, which is a new record for organic monolayer transistors and opens up a new pathway for bottom-up organic electronics. Third, the surface organization of a conjugated polymer is precisely modulated from edge-on to face-on arrangement by solvent tuning. Trichlorobenzene (TCB) is found to be effective to avoid the polymer aggregation in solution, and the surface organization of resultant thin films shows a transition from edge-on to face-on. Last but not least, a new solution processing approach, two-phase dip-coating, is proposed to align ultrathin films of organic semiconductors, with the application of a surfactant as an assistant agent and a phase-separated binary liquid mixture. In particular, this method is applicable to the conjugated compounds with poor solubility. The aligned microstripes consist of only a few monolayers, but exhibit bulk-like transistor performance, indicating that the first few monolayers adjacent to the dielectric play a dominant role in charge carrier transport.
DDC:	540 Chemie 540 Chemistry and allied sciences
Institution:	Johannes Gutenberg-Universität Mainz
Department:	FB 09 Chemie, Pharmazie u. Geowissensch.
Place:	Mainz
ROR:	https://ror.org/023b0x485
DOI:	http://doi.org/10.25358/openscience-2497
URN:	urn:nbn:de:hebis:77-diss-1000004855
Version:	Original work
Publication type:	Dissertation
License:	In Copyright
Information on rights of use:	https://rightsstatements.org/vocab/InC/1.0/
Extent:	197 S.
Appears in collections:	JGU-Publikationen