All jet-printed polymer thin film transistor active-matrix backplanes (Invited talk)
The use of solution-processed materials in combination with simple printing technologies offers the promise of inexpensive fabrication of active matrix backplanes for large area flexible displays. We report additive jet-printing of regioregular polythiophene thin film transistors (TFT), and a printing process to fabricate complete prototype active matrix TFT arrays. We integrated metals and inorganic dielectric materials processed at low temperatures with a polymeric semiconductor to allow the use of flexible substrates. Patterning of metal gate, source and drain features and address lines uses digital lithography to jet-print a wax etch-mask. Once the wax mask is printed, the metal layer is patterned by etching and the wax is removed. The polymer solution is printed from a piezo-jet printhead. Additive jet printing was chosen as the preferred method of polymer deposition in order to achieve semiconductor isolation and reduce the cross talk leakage between transistors in the array. The jetted polythiophene semiconductor exhibits TFT mobility of ~0.1 cm2/Vs, on/off ratios of 107, and minimal bias-stress, showing that the process of jet-printing results in the same electronic properties as in spin-coated films. These TFT parameters approach the performance of amorphous silicon transistors and meet the requirements for addressing displays. We fabricated 128X128 pixel active matrix backplanes with 340 micron pixel size, corresponding to 75 dpi display resolution, on glass and flexible substrates. This is the largest number of printed transistors and the highest display resolution reported by ink jet printing. We show that pixel design benefits from the registration accuracy of jet-printing and that the electrical performance is suitable for addressing capacitive media displays. Integration of display media to the array will be discussed.
Arias, A. C. ; Ready, S. E. ; Lujan, R. A. ; Wong, W. S. ; Paul, K. ; Chabinyc, M. ; Salleo, A. ; Street, R. A. All jet-printed polymer thin film transistor active-matrix backplanes (Invited talk). ACS National Meeting; 2004 August 22-26; Philadelphia; PA.