Optoelectronic Properties of ZnO Nanoparticle/Pentacene Heterojunction Photodiode

We fabricated photodiodes based on planar heterojunctions of zinc oxide (ZnO) nanoparticles (NPs, ～5 nm) and pentacene. The current density–voltage (J–V) characteristics of the photodiodes were investigated in the dark and under illumination. The photodiodes had good rectifying behavior in the dark and under illumination. A high rectification ratio (RR) of 878 at ±1.75 V and a low turn-on voltage of 1.3 V were achieved in the dark. Under 100 mW/cm² illumination, an RR of 55.3 was obtained at ±1.90 V. Furthermore, the photoresponsive mechanism of the device was explained in terms of the schematic band diagram and the transport of charge carriers in the device.