Investigation of the temperature-dependent electrical properties of Au/PEDOT:WO3/p-Si hybrid device

Abstract

The electrical properties of Au/PEDOT:WO3/p-Si hybrid devices were studied in terms of current–voltage (I–V) and capacitance–voltage (C–V) measurements. Poly (3,4-ethylene dioxythiophene/tungsten trioxide (PEDOT:WO3) composite was prepared by an in situ chemical oxidative polymerization of monomer in 1-butyl-3-methylimidazoliumtetrafluoroborate (BMIMBF4). Optical and structural properties of the PEDOT:WO3 thin film was characterized by using FTIR, UV–Vis and AFM techniques. The bandgap energy of PEDOT:WO3 thin film was determined as 2.07 eV from UV–Vis spectrum. It was seen that the I–V plots of the Au/PEDOT:WO3/p-Si hybrid devices were non-linear and C−2–V plots were linear in the reverse bias defining rectification behavior. The values of barrier height obtained from the I–V and C−2–V plots of the fabricated devices were found to be 0.729 ± 0.012 eV and 0.817 ± 0.011 eV at room temperature in the dark environment, respectively. Devices have a high rectification behavior with a rectification ratio of 3.645 × 105 at ± 1 V. The temperature-dependent I–V characteristics of one of the devices were also analyzed on the basis of the thermionic emission theory at low forward bias voltage regime. It was observed that the values of ideality factor decrease while the values of barrier height increase with increasing temperature. This kind of temperature dependence was attributed to the presence of the barrier inhomogeneity at the hybrid film/inorganic semiconductor interface. Then, by analysing of the forward bias I–V characteristics at double logarithmic scale, it was seen that the carrier transport in the Au/PEDOT:WO3/p-Si hybrid device demonstrates the space-charge-limited current (SCLC) conduction mechanism controlled by a trap distribution above the valence band edge dominates in the range 0.1–0.3 V voltages. Furthermore, by analyzing the reverse bias I–V–T characteristics, it was shown that Schottky emission was the dominating current conduction mechanism in the temperature range of 240–320 K.