Solution processable bilayered gate dielectric towards flexible organic thin film transistors

Ranjodh Singh, Jagan Singh Meena, I. Hsin Tsai, Yen Ting Lin, Cheng Jyun Wang, Fu-Hsiang Ko*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


In this study, we have successfully explored the potential of a new bilayer gate dielectric material, composed of Polystyrene (PS), Pluronic P123 Block Copolymer Surfactant (P123) composite thin film and Polyacrylonitrile (PAN) through fabrication of metal insulator metal (MIM) capacitor devices and organic thin film transistors (OTFTs). The conditions for fabrication of PAN and PS-P123 as a bilayer dielectric material are optimized before employing it further as a gate dielectric in OTFTs. Simple solution processable techniques are applied to deposit PAN and PS-P123 as a bilayer dielectric layer on Polyimide (PI) substrates. Contact angle study is further performed to explore the surface property of this bilayer polymer gate dielectric material. This new bilayer dielectric having a k value of 3.7 intermediate to that of PS-P123 composite thin film dielectric (k ∼ 2.8) and PAN dielectric (k ∼ 5.5) has successfully acted as a buffer layer by preventing the direct contact between the organic semiconducting layer and high k PAN dielectric. The OTFT devices based on α,ω-dihexylquaterthiophene (DH4T) incorporated with this bilayer dielectric, has demonstrated a hole mobility of 1.37 × 10-2 and on/off current ratio of 103 which is one of the good values as reported before. Several bending conditions are applied, to explore the charge carrier hopping mechanism involved in deterioration of electrical properties of these OTFTs. Additionally, the electrical performance of OTFTs, which are exposed to open atmosphere for five days, can be interestingly recovered by means of re-baking them respectively at 90 °C.

Original languageEnglish
Pages (from-to)120-130
Number of pages11
JournalOrganic Electronics
StatePublished - 1 Jan 2015


  • Device performance restore
  • Flexible device
  • Gate dielectric
  • Organic thin film transistor
  • Solution processing


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