Conference Program - LOPE-C 2011

SCIENTIFIC CONF. | WEDNESDAY-JUNE 29, 2011
Track 4
Organic Transistors (02:30 pm - 04:00 pm) | LOCATION HARMONIE D / LEVEL C2
03:40 pm Dynamic Characterization of Charge Injection and Transport by
Mr Jack Lin,
Tokyo Institute of Technology, Japan
Semiconductor devices using organic materials, such as thin film transistors, light emitting diodes, and solar cells, have attracted a lot of research and commercial interests.
The importance of basic research on the injection, accumulation, and transport mechanisms has also become more recognized to understand and improve the device
performance. This paper introduces some enabling technologies that allow us to gain better understanding of the working mechanism of organic field-effect transistors
(OFET), especially in the transient state.
Direct imaging of carrier motion in OFET has been realized by the time-resolved microscopy optical second harmonic generation (TRM-SHG) technique, where the SHG
light intensity is proportional to the square of the local electric field. The time resolved measurement was achieved by varying the delay time of the laser pulse in relation to
the applied voltage precisely. By selecting the appropriate wavelength, the electric field induced SHG can be used to selectively probe the specific organic material of
interest in complex multilayered systems. In this paper, we show results of carrier propagation in pentacene OFET obtained by TRM-SHG. Furthermore, contact resistance
was also investigated by the potential drop which was directly evaluated from SHG.
In combination with the electrical time-of-flight technique and impedance spectroscopy, along with conventional current-voltage measurements, it is possible to investigate
the transient-state and steady-state behaviors of the OFET. The difference between these states is attributed to the filling of traps. Further study of the trapping states have
been carried out by partially charging the gate-semiconductor interface (partially filling the traps) and investigating the device?s temperature dependence.
Additionally, we introduce the newly developed technique to use time-resolved SHG for evaluation of carrier injection, recombination, and exciton generation processes in
organic light-emitting diode and organic solar cells.
04:00 pm COFFEE BREAK
page 61