Design, Fabrication and Characterization of
MultifunctionalField-Effect Transistors (FETs)
based on novel n-conjugated organic semiconductors.
Université du Québec, Institut national de la recherche scientifique, Doctorat en sciences de l'énergie et des matériaux, 140 p.
For over 50 years the mainstream electronics industry has been dominated by thin film
transistors based on inorganic semiconductors such as silicon and gallium arsenide. The
fabrication of these devices requires high temperature and high vacuum deposition
techniques that result in high production costs, which are particularly prohibitive for large-area
Organic semiconductors (OSCs) offer an attractive alternative since their fabrication
processes are much less complex compared to conventional inorganic technology. In
particular, low temperature deposition and solution processing techniques provide a simple,
low cost alternative. π-Conjugated organic semiconductors are therefore attracting
considerable attention for applications such as organic light-emitting diodes (OLEDs), field-effect
transistors (OFETs) and photovoltaic cells. Furthermore, the mechanical properties
(flexibility) of organic compounds coupled with their low temperature solution-based
processing provides the potential for new applications inc1uding flexible displays, pliable
electronic paper and smart cards. While molecular and polymer OLEDs have already been
commercialized in a number of consumer products, OLED displays still employ an inorganic
(amorphous silicon, a-Si) thin-film transistor (TFT) matrix to control the emissive pixels.
Organic TFTs (OTFTs) are nevertheless extensively investigated by numerous, both
industrial and academic, research groups. The mobility of the best OSCs have already
approached and even surpassed that of a-Si (~1 cm² V/s). However, the limited stability of
OSCs and the "difficult to control" molecular packing, particularly in solution-processed
devices, are among the major limitations hampering industrial development, and the design
of new OSCs continues to be an important area of materials research.
This project involves elaboration of the thin film technology of new organic semiconducting
materials, inc1uding small molecules (fused polyaromatic systems and heterocyc1ic
oligomers, mainly fused thiophene and selenophene derivatives) and polymers, and
characterization of their electronic properties for applications in optoelectronic devices. A
large emphasis of this project is the study of new organic materials as an active
semiconducting layer in transistors. Along the typical switching function of OTFTs, the
research is directed to the design, fabrication and characterization of multifunctional
transistors that can have electroluminescence and possible lasing properties.
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