There has been a great interest in the realization of low-cost and large-area manufacturing methods for flexible electronic applications such as lighting displays, organic photovoltaics, thin film transistors, 3D batteries, etc. Printed electronics has become the most promising technology due to its lithography- and vacuum-free processing. On the other hand, many nanoscale functional materials such as nanowires, nanotubes, nanoparticles, supermolecules, biomaterials, etc., have been developed. In order to use them as active materials for electronic devices, precise drop-on-demand technique with extremely small volume has been desired. In this regard, solution-processed nanomaterials have been advanced rapidly to enhance the performance of printed electronic devices.

In this work, an a...[ Read more ]

There has been a great interest in the realization of low-cost and large-area manufacturing methods for flexible electronic applications such as lighting displays, organic photovoltaics, thin film transistors, 3D batteries, etc. Printed electronics has become the most promising technology due to its lithography- and vacuum-free processing. On the other hand, many nanoscale functional materials such as nanowires, nanotubes, nanoparticles, supermolecules, biomaterials, etc., have been developed. In order to use them as active materials for electronic devices, precise drop-on-demand technique with extremely small volume has been desired. In this regard, solution-processed nanomaterials have been advanced rapidly to enhance the performance of printed electronic devices.

In this work, an all-printed ZnO granular polycrystalline nanowires based UV photodetector with ultra-high detectivity was fabricated on flexible substrate. Systematic investigations have shown their ultra-high photoconductive gain, responsivity and detectivity up to 3.3×10¹⁷ Jones. Further analysis shows that their high performance originates from the unique band-edge modulation along the nanowire axial direction, where the existence of Schottky barriers in series leads to highly suppressed dark current of the device and also gives rise to fast photoelectric response to low-intensity optical signal owing to barrier height modulation. The discovered rationale in this work can be utilized as guideline to design high-performance photodetectors with other nanomaterial systems. The developed fabrication scheme opens up possibility for future flexible and high-performance integrated optoelectronic sensor circuitry.

However, the poor resolution of state-of-the-art printing techniques has necessitated the use of large channel lengths in transistors and large gate to source/drain overlap to compensate for the poor layer-to-layer registration capability. These large dimensions have limited the speed improvement in printed transistors, despite the improvements in materials. Therefore, a novel near-field electrospinning PVA nanofibers assisted method was developed to largely decrease the channel length to ~500nm, contrasted to the >50 μm typically required in conventional printed transistors. Furthermore, the three-dimensional CNTs transistors were schematically integrated by this method and the initial single layer CNTs transistors are characterized and measured.