Research On Flexible Display Driving Circuits Based On Carbon Nanotube Thin Film Transistors

With the development of display technology,the display device has been transited from CRT to LCD,and flexible display will become the trend of display devices.Due to its self-emission,low power consumption,wider viewing angles,high brightness,fast response time,lightweight and flexible plastic substrates,active matrix organic light emitting diode(AMOLED)display holds great potential for the next generation visual technologies.Flexibility,high stability,low temperature process of thin film transistor(TFT)is required to realize the advantages of AMOLED.So the preparation of high performance TFT and driving circuit are the key to achieve flexible AMOLED.Single Walled Carbon Nanotube(SWCNT)is an ideal one dimension nano-material,which has excellent electrical,optical,thermal and mechanical properties.Using SWCNT as the channel materials can achieve different structures of the carbon nanotube thin film transistors(CNTTFTs)and high performance driving circuit for AMOLED.Based on the character of CNTTFTs,a research on flexible display driving circuits was studied.First,the performance of the CNTTFTs with different channel length and width were evaluated.By optimizing the electrical properties of CNTTFTs,the appropriate channel length and width were selected,and then the model of the CNTTFT and the logic of driving circuit were built and verified.Second,based on the traditional 2T1C pixel driving circuit and taking the appropriate size of TFT,the capacitance and the aperture ratio of the display into consideration,the layout of the driving circuit was built by L-edit software.Third,a kind of effective method by using polymer materials as the gate insulation layer to fabricate the flexible display driving circuit was proposed.Compared to SiO2,Al2O3 and other insulation layer,this method not only simplified the process,but also was an effective method to prepare flexible gate insulating layer.Finally,the pixel driving circuit was fabricated on silicon wafer,glass and flexible substrate(PEN)by taking photoresist as the insulation layer.For carbon nanotubes film with high quality,the single pixel unit demonstrated an on current of 10 ?A,a current on/off ratio of 105 and a hole mobility of 65 cm2/Vs,which offered high enough current to drive the designed OLED.According to the results of bending test and fatigue resistance test,there was no big change in performance of the circuits and TFTs under the bending deformation.This research was meaningful for the large scale AMOLED display.