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Abnormal temperature-dependent electron transport in hole
transport material TPD
Yun He, Yongmao Hu, Xiaoqing Chen, Huan Pen and Xiaoyuan Hou
Phys. Dept., Fudan Univ., Shanghai, People’s Republic of China
Abstract：Electron currents in N,N’-diphenyl-N,N’-bis(3-methylp-henyl)- (1,1’-biphenyl)-4,4’-diamine (TPD)
thin films were studied. It is found that temperature dependence of electron conduction of TPD varies with
driving voltage: in low voltage range the electron conduction almost keeps unchanged, and in the mid-voltage
range it increases with temperature, while in the high voltage range it decreases abnormally with increasing
temperature.
Many works have showed that the conduction of organic
material increases with increasing temperature, and the
experimental results could be well fitted by either trappedcharge-limited current (TCLC) with an exponential trap
distribution or space-charge-limited current (SCLC) model [1].
However, we find that temperature dependence of electron
conduction of TPD varies with driving voltage: in the range of 07 V the electron conduction almost keeps unchanged, and in the
range of 10-30 V it increases with temperature, while in the
range of 30-35 V it decreases abnormally with increasing
temperature (see Fig.1).
Fig.2
Fig.3
Fig.1
Fig.4
Summary: Temperature dependence of electron conduction in TPD is voltage dependent. Models TCLC
with exponential trap distribution and SCLC with field-dependent mobility are used to interpret the
experimental data, but neither one can apply to explain the experimental results for the whole voltage range.
References:
[1]X. D. Gao, Yun He et al, Appl. Phys. lett. 95, 133306(2009).