Copper Oxide-Based Schottky Diode Using Poly(3-hexylthiophene) as an Interlayer

We report the electrical properties and charge transport behavior of an electrodeposited, vacuum-annealed (100 °C) pure Cu₂O and air-annealed (at 300 °C) Cu-O (mixed phase of Cu₂O and CuO) films in the device geometry of ITO/Cu₂O/Al and ITO/Cu-O/Al. An intermediate poly-(3-hexylthiophene) (P3HT) layer was deposited by spin coating to fabricate devices with the structures ITO/Cu₂O/P3HT/Al and ITO/Cu-O/P3HT/Al. The incorporation of P3HT significantly alters the device characteristics from ohmic to Schottky-type behavior. The device ITO/Cu₂O/P3HT/Al shows better <i>I-V</i> characteristics compared to ITO/Cu-O/P3HT/Al in terms of its lower leakage or reverse saturation current (of the order ∼10^-7 mA). Furthermore, the Schottky barrier height (φ_B) at P3HT/Al for both devices is of the same order ∼0.9 eV. Impedance Spectroscopy (IS) measurements were performed on all the devices in the frequency range of 40 Hz-100 MHz to understand the device characteristics and AC charge transport phenomenon. An equivalent circuit model with two RQ parallel (Q: constant phase element) components in series best fits the IS data, highlighting the separate roles of bulk and interfacial effects. Mott-Schottky analysis confirms p-type behavior for Cu₂O films, whereas Cu-O exhibits n-type characteristics arising due to oxygen vacancies. This work demonstrates the potential of Cu₂O/P3HT interface engineering for optoelectronic device applications.