Gate-Bias Stability Behavior Tailored by Dielectric Polymer Stereostructure in Organic Transistors.
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, iso-, syn-, 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 (iso- and syn-stereoisomers) exhibited more stable OFET operation under bias stress compared to devices prepared using irregular a-PMMA in both vacuum and air.
Department of Chemical and Biological Engineering, Hanbat National University , Daejeon 305-719, Korea.
Junghwi
J
Lee
Department of Chemical and Biological Engineering, Hanbat National University , Daejeon 305-719, Korea.
Honggi
H
Min
Department of Chemical and Biological Engineering, Hanbat National University , Daejeon 305-719, Korea.
Namwoo
N
Park
Department of Chemical and Biological Engineering, Hanbat National University , Daejeon 305-719, Korea.
Heejeong
H
Jeong
Department of Chemical and Biological Engineering, Hanbat National University , Daejeon 305-719, Korea.
Singu
S
Han
Department of Nano, Medical, and Polymer Materials, Yeungnam University , Gyeongsan 712-749, Korea.
Se Hyun
SH
Kim
Department of Chemical and Biological Engineering, Hanbat National University , Daejeon 305-719, Korea.
Hwa Sung
HS
Lee
configurational arrangement; operational stability; organic field-effect transistor; polymer dielectric; polymer stereostructure