Achieving time-of-flight mobilities for amorphous organic semiconductors in a thin film transistor configuration

Cyrus Y.H. Chan, K. K. Tsung, W. H. Choi, Shu Kong SO*

*Corresponding author for this work

Research output: Contribution to journalJournal articlepeer-review

30 Citations (Scopus)


We observe bulk-like hole transport in amorphous organic semiconductors in a thin film transistor (TFT) configuration. Five different organic hole transporters (HTs) commonly used in organic light-emitting diodes are investigated. When these HTs are deposited on SiO2 gate dielectric layer, the TFT mobilities are 1-2 orders of magnitude smaller than those obtained from bulk films (3-8 μm) using time-of-flight (TOF) technique. The reduction of hole mobilities can be attributed to the interactions between the organic HTs and the polar SiO bonds on the gate dielectric layer. Detailed temperature dependence studies, employing the Gaussian disorder model, indicate that the SiO2 gate dielectric contributes between 60 and 90 meV of energetic disorder in the charge hopping manifold. Besides SiO2 gate dielectric, similar effects can also be observed for other polar insulators including polymeric PMMA and BCB, or HMDS-modified SiO2. However, when a common non-polar polymer, polystyrene (PS), is employed as the dielectric layer, the dipolar energetic disorder becomes negligible. Holes effectively experience bulk-like transport on the PS gate dielectric surface. TFT mobilities extracted from all five organic HTs are in excellent agreements with TOF mobilities. The present study should have broad applications in the transport characterization of amorphous organic semiconductors.

Original languageEnglish
Pages (from-to)1351-1358
Number of pages8
JournalOrganic Electronics
Issue number5
Publication statusPublished - May 2013

Scopus Subject Areas

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Chemistry(all)
  • Condensed Matter Physics
  • Materials Chemistry
  • Electrical and Electronic Engineering

User-Defined Keywords

  • Gate dielectrics
  • Interfacial dipoles
  • Thin film transistor
  • Time-of-flight


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