Ultraviolet photodetectors based on low temperature processed ZnO/PEDOT:PSS Schottky barrier diodes

In this work, vertical Schottky barrier diodes (SBDs) were fabricated using a thin film of ZnO (50 nm) and PEDOT:PSS deposited by RF Sputtering and micro-drop casting, respectively. ITO and Au were used as ohmic contacts to ZnO and PEDOT:PSS films, respectively. The final structure consisted on Glass/ITO/ZnO/PEDOT:PSS/Au. The SBDs performance was characterized under dark and four different wavelengths conditions. From current–voltage characteristics, under dark and ambient conditions, a diode ideality factor of 1.4; a saturation current density of 1×10−9 A/cm2; a Schottky barrier height of 0.9 eV and a rectification ratio of 5 orders of magnitude at ±1 V were obtained. A carrier density of 5×1017 cm−3 for the ZnO film was estimated from capacitance–voltage measurements. For their characterization as photodiodes, the SBDs were illuminated with an ultra-bright UV (~380 nm) LED. A maximum UV responsivity of 0.013 A/W was obtained. The transient response of the SBDs was also analyzed with the UV LED connected to a pulsed signal of 0.5 Hz, demonstrating rise and fall times in the order of 200 ms. With a low temperature processing (<80 °C), visible-blind and UV photon-detection characteristics, the fabricated SBDs are candidates for flexible optoelectronics devices such as optical receivers for digital signal processing and measurement of light intensity.