Polymer-Doped Printed Metal Oxide Thin Film Transistors

In recent years,due to the rapid development of the display industry,thin-film transistor technology has attracted much attention.Metal oxide thin-film transistor(MOTFT)has been extensively studied for their excellent electrical and optical properties and is widely applied in high resolution active matrix liquid crystal displays,large-area memory arrays and sensors.Comparing with the conventional vacuum-based technologies,intensive efforts have been made on the fabrication of MOTFTs using solution-processing methods,which enable the low-cost and large-area fabrication of metal oxide semiconductor films.However,most study of solution-processed MO was focused on single cell using spin coating,while patterned TFT arrays are intensively required for the commercialization.As one of promising thin film fabricated techniques,inkjet printing(IUP)has many advantages such as eliminating costly masking steps and direct-writing of high resolution TFT arrays,which has great potential to replace conventional TFTs fabrication technology.Therefore,it is crucial to study the inkjet printing of solution-processed oxide thin film transistors.This work will use the inkjet printing technology to fabricate the oxide thin film transistor,and study the morphology and electrical properties of the inkjet printed films from the perspective of ink formulation and printing process.Specific research content includes the following aspects:1.Using inkjet printing technology to study the effects of different surface treatments and substrates with different temperatures on the quality of the printed film.The surface morphology of the printed film was examined through a profiler and a polarizing microscope.The dot pitch and printing speed were adjusted to obtain the optimized process parameters for printing and the phenomenon of the coffee ring of the film was well studied.The results showed that the appropriate process parameters are conducive to improve the non-uniform of the printed film morphology.2.To solve the problem of non-uniformity in the film,a polymer doping method was used.By changing the molecular weight of the doped polymer,the changes in the morphology and properties of the device were investigated.The results show that doping with a suitable molecular weight polymer improves the unevenness of the inkjet printing pattern and suppresses the coffee ring phenomenon of the film.Compared with the undoped ink,the doping of this molecular weight polymer facilitates the formation of the M-O network in the film and the inhibition of crystallization,and the device mobility increases from 4.2 cm-2V-ls-1 to 13.7 cm-2V-1s-1.3.Based on the optimization of the uniformity of the doping of the polymer by the doping of the polymer to improve the performance of the device transistor,a vertical structure thin film transistor compatible with the printing process is further designed.Through mechanism analysis and structural design,a mesh electrode is prepared by a spin coating process and combined with inkjet printing process,which realizes the preparation of a vertical structure thin film transistor matrix.The experimental results show that the grid electric field can realize the regulation of the active layer on and off through the mesh electrode,and the device can work normally.Its current density can increase to 11mA/cm2 when it is turned on,suitable for AMOLED display technology which requires high current density.Meanwhile,its switching capability still has a lot of space to improve.