Research On Aerosol Jet Printing Technology And Its Application In Organic Thin-film Transistor

Organic thin film transistors （OTFT） have attract more and more attention due to theirunique advantages such as low cost, easy processability and abundant organic materialstogether with their potential electric applications in large area processing and flexiblefabrication. As a new micro design machining technology, Aerosol-Jet printing is graduallybecoming an ideal method to fabricate electronic devices such as displays, efficient solar cellsand sensors.In this thesis, electrode layer, semiconductor layer and insulating layer of OTFT werepreparation and representation utilizing Aerosol-Jet printing technology. Besides, OTFTs werefabricated, which the electrodes of PEDOT:PSS and silver were obtained by Aerosol Jetprinting technology. The performance of the OTFT was tested and compared. As well as, Allprinted OTFT was fabricated by Aerosol Jet printing technology and the performance wastested and analysed. The main contents include:（1） The film of conducting polymer PEDOT:PSS was fabricated by Aerosol Jet printingtechnology. The effects of the different solvents such as ethylene glycerol and glycerol onsatellite particle, morphology and conductive properties of the films were studied in detail byOptical image, atomic force machine （AFM）, four-probe method. Furthermore, the effects ofinserting the Ag nanowires or grapheme in the PEDOT:PSS mixed solvent have beendiscussed. It has been experimentally found that addition of ethylene glycol and glycerol caneffectively control the satellite particles, reduce the roughness. The RMS is reduced from266nm to47.7nm, and2.99nm, respectively after employing the solvent of ethylene glycol andglycerol. Moreover, the conductivity of PEDOT:PSS film is enhanced obviously. The sheetresistance of the films is reduced from the3.31×10⁸Ω/口to4.53×10⁵Ω/口, and4.61×10⁴Ω/口, respectively by inserting the ethylene glycol and glycerol solvent. What is more, theconductivity of PEDOT:PSS film is enhanced particularly by inserting the Ag nanowires andgrapheme. The sheet resistance of the films is reduced from the3.16×10³Ω/口to321Ω/口,and267Ω/口, respectively. （2） The film of semiconductor material P3HT was fabricated by Aerosol Jet printingtechnology. The effects of the different solvents and printing parameters on morphology andthickness of the films were studied in detail by Optical image, AFM and Step-height Profilermethod. It has been experimentally found that chloroform with terpinol is the best solvent inthe preparation of the semiconductor material P3HT with Aerosol Jet printing technology.The best quality of P3HT film can be obtained under the condition that mist flow rate is10^<sup>mland the printing is conducted at the speed of0.5mm/s or1mm/s. Moreover, when otherparameters fixed, the deposition film is becoming thinner when printing speed is faster andmist flow rate is smaller. On the contrary, the deposition film is becoming thicker whenprinting speed is slower and mist flow rate is larger.（3） The film of insulating material PMMA and PMMA with ionic liquid was fabricatedby Aerosol Jet printing technology. The effects of the different solvents and differentproportion of solvents on morphology and thickness of the films were studied in detail byOptical image, AFM and four-probe method. The results proved that the best quality film wasmade using PMMA with ionic liquid （3wt%:7wt%） in anisole. Under this condition, thedielectric constant of film was highest and was more suitable for insulating layer of OTFT.（4） The OTFTs were fabricated, which the electrodes of PEDOT: PSS and silver wereobtained by Aerosol Jet printing technology. The performance of the OTFT was tested andcompared by the four-probe method. The results indicated that the performance of the OTFTwith different electrodes were similar. Carrier mobility of the two OTFTs were1.1×10^-3cm²V^-1s^-1and2.9×10^-3cm²V^-1s^-1, respectively.（5） All printed OTFT was fabricated by Aerosol Jet printing technology. Theperformance of the OTFT was tested by the four-probe method. The results indicated that thisdevice was saturated at3V with lower driving voltage. This is mainly due to the highdielectric constant of insulating materials which can effectively reduce the working voltage ofdevices.