Hysteresis-free DC conduction in zinc oxide films with a conducting polymer counter electrode

Abstract

A conducting polymer, namely poly (3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has been employed as an alternative metal counter electrode to study steady state charge conduction through a spin-coated 5.2 µm thick ZnO film in a sandwich structure on a fluorine doped tin oxide (FTO) coated glass substrate. The room temperature current-voltage characteristics exhibit rectifying behaviour without hysteresis as the bias voltage is cycled between ±10V for varying voltage sweep rate from 100mV/s to 1000mV/s. Thermionic emission is believed to be the dominant conduction mechanism at forward bias voltage V ≤ 2.5V whereas the space charge limited current conduction becomes effective in a higher voltage region V>2.5V. The barrier height (b), ideality factor (n) and series resistance (Rs) are found to be strongly temperature dependent parameters showing the increase of ϕ_band simultaneous decreases of n and Rs within the range of 218K-298K. The behaviour of the temperature dependent charge carrier mobility in the higher voltage region has also been discussed. The use of PEDOT: PSS is quite promising as an alternative to metal electrodes in semiconductor devices.