Exploring the temperature-dependent hole-transport in vanadyl-phthalocyanine thin films

In this paper, the dc electrical properties of Vanadyl phthalocyanine (VOPc) thin films were explored in a hole-only device configuration: ITO/MoO3/VOPc/MoO3/Al. The fabricated diode device was investigated using current density-voltage (J-V) characteristics by varying the substrate temperature from 303 K to 373 K with an interval of 5 K. The barrier height at the ITO/VOPc interface was observed to be reduced from 500 meV to 428 meV as temperature increases. The electrical conduction mechanism was found to be space charge limited currents with exponential trap distribution. Further, the hole-mobility was realized to increase from 1.7 x 10(-7) cm(2)V(-1)s(-1) to 1.2 x 10(-5) cm(2)V(-1)s(-1) (2 orders) with a rise in temperature from 303 K to 373 K. The effective trap density in our device was estimated as N-t similar to 5.5 x 10(22) m(-3). However, the improved hole-mobility with temperature is attributed to the enhanced injection of charge carriers (thermally generated) along with the reduction of barrier height.