The Study Of Inkjet-printed Vertical Organic Transistors And Their Applications

Organic thin film transistors(OTFTs)have been widely explored due to their unique properties such as chemical diversity,solution processing and flexibility.However,some intrinsic disadvantages of conventional OFETs have been reported in recent research such as low current density,inferior operating speeds,and relative poor mobility compared to inorganic materials.In order to overcome these limitations,from the perspective of geometry,vertical OFET(VOFET)architecture has recently been explored to overcome the performance limitations of conventional lateral-channel OTFT structures.Unfortunately,the state-of-the-art of the fabrication of solution-processed VOFETs is still immature.The vacuum process cannot meet the low-cost and large-area requirements of organic transistors,while the solution process is too complicated,which can only focus at a single-cell level.Combined with the solution preparation,low cost and optional patterning of the new inkjet printing technology,this work innovatively used inkjet printing to fabricate VOFET,successfully simplifying the fabrication process.Moreover,solution processed VOFET array was achieved for the first time.In addition,for the first time,focusing on different bending conditions and illumination conditions,this research studied the influence of different situation on VOFETs,and realized its application in flexible image sensors for the first time.The research was conducted step by step,which included the following three aspects:1.The key steps of the fabrication of solution processed VOFET,pattern of active layer and the deposition of source contact and drain,were achieved by inkjet printing,and the fabrication process of the VOFET array was presented.The array was characterized and the working mechanism of the device was described.Finally,a VOFET array with excellent performance and good uniformity was obtained.2.A flexible VOFET array was fabricated and electrical characterization under bending conditions was performed to reveal the effect of bending conditions on VOFET.It is found that the mechanical stability of VOFET is much higher than that of traditional structure OTFT.The analysis of the VOFET architecture revealed that vertical transmission can effectively avoid the influence of defects in layers under the bending condition on carrier transmission.3.The application of VOFET in flexible image sensor was realized.The VOFET image sensor was characterized by optical response,and the operation of the VOFET influenced by light was studied.Compared with the traditional OTFT photodetector,the optical detection performance of VOFET was significantly improved.It is explored that the ultra-short channel of the VOFET architecture facilitates the rapid separation and transmission of photogenerated excitons,and the vertical transmission avoids the capture of photo-generated carriers by the interlayer interface.