Gate-Bias Stability Behavior
Tailored by Dielectric Polymer Stereostructure in Organic Transistors
- Publication date
- Publisher
Abstract
Understanding
charge trapping in a polymer dielectric is critical to the design
of high-performance organic field-effect transistors (OFETs). We investigated
the OFET stability as a function of the dielectric polymer stereostructure
under a gate bias stress and during long-term operation. To this end, <i>iso</i>-, <i>syn</i>-, and atactic poly(methyl methacrylate)
(PMMA) polymers with identical molecular weights and polydispersity
indices were selected. The PMMA stereostructure was found to significantly
influence the charge trapping behavior and trap formation in the polymer
dielectrics. This influence was especially strong in the bulk region
rather than in the surface region. The regular configurational arrangements
(isotactic > syntactic > atactic) of the pendant groups on the
PMMA backbone chain facilitated closer packing between the polymer
interchains and led to a higher crystallinity of the polymer dielectric,
which caused a reduction in the free volumes that act as sites for
charge trapping and air molecule absorption. The PMMA dielectrics
with regular stereostructures (<i>iso</i>- and <i>syn</i>-stereoisomers) exhibited more stable OFET operation under bias stress
compared to devices prepared using irregular <i>a</i>-PMMA
in both vacuum and air