Fully Aerosol-Jet Printed, High-Performance Nanoporous ZnO Ultraviolet Photodetectors

We report fully aerosol-jet printed ultraviolet photodetectors based on zinc oxide nanocrystal networks having a porous morphology. The developed photodetectors exhibit selective optical photoresponse in the ultraviolet spectrum at wavelengths ranging from 250 nm up to 400 nm. These devices show a high ON/OFF ratio of ∼106 and short response times. The characteristic time constants for the rise and fall edges were measured to be ∼0.4 and ∼1.3 s, respectively. In this work, we propose a direct approach for aerosol-jet printing of presynthesized nanocrystals to overcome the limitations of high post-annealing temperatures and tedious fabrication methods to obtain high aspect ratio nanostructures. The high performance characteristics of these devices are attributed to Schottky barrier modification under the influence of oxygen, which is enhanced by the porosity of the semiconductor material. The random orientation of the crystals aids the formation of air traps in the network, thereby enhancing the surface area to volume ratio. Most importantly, the complete processing of these devices is performed below 150 °C, which makes this technology compatible with the processing on a wide range of mechanically flexible, recyclable, or inexpensive substrates such as paper and plastics.