Analytical Sciences

Carrier Mobility for Organic Semiconductors: Reduction of Noise of the Short Part Drift Time in the Time of Flight Mobility Method

Ken KASHIMA,* Hiroshi SATO,** Kiyoshi MUSHA,*** Ken-ichiro KANNO,* and Tamotsu TAKAHASHI*

*Catalysis Research Center and Graduate School of Life Science, Hokkaido University, Sapporo 001-0021, Japan
**System Department, Bunkoh Keiki, Co., Ltd., Takakura, Hachioji, Tokyo 192-0033, Japan
***Advanced Materials R & D Laboratory, ADEKA, Higashi-Ogu, Arakawa, Tokyo 116-8553, Japan

Measurements of time of flight (TOF) mobility of organic semiconductors become difficult when the mobility values are high, since the electronic signals overlap with the noise of the short part in drift time. Such noise of the short part in the drift time in the TOF method for measurements of carrier mobility was reduced by three methods: (1) longer distance (3.5 m) between sample and the N₂ laser, (2) optical connection (photo coupler) between the N₂ laser and the pulse generator, and (3) using a digital filter to remove characteristic pulses caused by N₂ laser. Each method showed significant reduction of the noise. When all three methods were applied, 94% of the noise was reduced. The measurement of TOF mobility was demonstrated with TPD (N,N′-diphenyl-N,N′-di(meta-tolyl)benzidine) film. Electronic signals in TOF measurements were clearly observed and the TOF mobility was determined to be 9.0 × 10^-4 cm²/V s.

J-STAGE: View this article in J-STAGE