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Printed polymer-based TFTs for flexible display backplanes

 

Additively printed polymer TFT arrays on plastic substrates can enable low cost displays with new functionality and performance. We present results and discuss the many challenges arising from the integration of solution processed materials such as printable metals, polymeric semiconductors and dielectric materials to fabricate display backplanes on flexible substrates. We use inkjet printing as the only patterning technique on the fabrication of display backplanes. Silver and gold nanoparticles are deposited from solution to form the conducting lines of the backplane. We show that the conductivity of printable metals fulfils the requirements for large area arrays. We have also developed a self encapsulating process where the semiconductor is blended with an insulating polymer from solution and during deposition the insulator material segregates to the top surface encapsulating the underlying semiconductor. Bottom gate TFT were fabricated with blends of semiconducting and insulating polymers at different concentrations and mobilities as high as 0.05 cm2/Vs were obtained. TFT devices were fabricated in air and showed stable sub-threshold voltages up to 21 days in air. This self-encapsulating process is compatible with inkjet printing and allowed the fabrication of 180X180 pixels array for display backplanes. We discuss pixel designs for TFT backplanes that benefit from the registration accuracy of jet-printing. Finally, we report results of long term electrical stress measurements of polymer semiconductor TFTs under display drive conditions which show that the small threshold voltage shifts consistent with AMLCD operation.

 
citation

Arias, A. C. ; Daniel, J. H. ; Apte, R. B. ; Endicott, F .; Lujan, R. A. ; Ready, S. E. ; Street, R. A. Printed polymer-based TFTs for flexible display backplanes. USDC Flexible Display & Microelectronics Conference; 2006 February 7-9; Phoenix; AZ; USA.