Transparent And Conducting Films Based On ITO Nanocrystals

Indium tin oxide (ITO) is a wide band-gap, highly doped n-type degenerate semiconductor material. Because of its high transparency in visible range and high conductivity, ITO is the most widely used transparent and conducting material. Traditional methods such as magnetron sputtering requires high vacuum and sophisticated equipment, and are not compatible with flexible plastic substrate. Solution-processed methods, which enable roll-to-roll processing to fabricate films on large-scale substrates with high speed, provide alternatives to produce high quality ITO films. Nevertheless, solution-processed ITO thin films often requires high-temperature annealing to improve the conductivity, which is not compatible with plastic substrates. It is of great interest to find a method to produce ITO films at low temperature (<200℃).Here, we report the synthesis of high quality ITO nanocrystals using hot-injection method. We employed low-temperature oxygen-plasma treatment on as-spin coated ITO films and discussed the mechanism.. The main contents are as followings:1. We synthesized ITO nanoflower particles with limited ligand protection mechanism, and detailed characterized the properties of both nanoflower and nanodot ITO.2. We chose common thermal annealing, along with oxygen plasma treatment on spin coated ITO nanocrystal films. The lowest resistivity prepared by oxygen plasma treatment is 2.33×10-2Ω·cm with 92% transparency in visible range. This is the lowest resistivity reported so far on low temperature solution processed ITO films. We further discussed the mechanism of oxygen plasma treatment on ITO films, and applied it on Cu/Ni alloy nanocrystal films.3. We applied the ITO nanocrystal films on the Polyethylene Naphthalate (PEN) substrate, which were produced by oxygen plasma treatment, as the transparent electrode for the flexible capacitive pressure sensor.