Electron transport properties of bis[2-(2-hydroxyphenyl)-pyridine]beryllium investigated by impedance spectroscopy

The electron transport properties of bis[2-(2-hydroxyphenyl)-pyridine] beryllium (Bepp2) are investigated by impedance spectroscopy over a frequency range of 10 Hz to 13 MHz. The Cole-Cole plots demonstrate that the Bepp2-based device can be represented by a single parallel resistance Rp and capacitance Cp network with a series resistance Rs. The current-voltage characteristics and the variation of Rp with applied bias voltage indicate the electron conduction of space-charge-limited current with exponential trap distributions in Bepp2. It can be seen that the electron mobility exhibits strong field-dependence in low electric field region and almost saturate in high electric field region. It is experimentally found that Bepp2 shows dispersion transport and becomes weak as the electric field increases. The activation energy is determined to be 0.043 eV by temperature-dependent conductivity, which is consistent with the result obtained from the temperature-dependent current density characteristics. The elect...