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 I x 10(-9) A/cm(2); 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 x 10(17) 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 (similar to 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 degrees C), visibleblind 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. (C) 2015 Elsevier Ltd. All rights reserved.