Improvement of Characteristics of OTFT with Bottom-contact Structure and its application to a Flexible Liquid Crystal Display Panel

We developed an organic thin-film transistor (OTFT) -driven 16×16 polymer-dispersed liquid crystal (PDLC) display panel on a flexible plastic film. We fabricated low-voltage-operation bottom-contact (BC) OTFT with Ta2O5 gate insulator, using photolithography method. This transistor is suitable for both scaling down and increasing the number of pixels, however its performance is inferior to that of top-contact OTFT because of contamination and defects on the surface of the insulator, and leakage-current of channel region. We have reduced the current of the OTFT by optimizing the pentacene deposition area. We used O2 plasma, UV cleaning and HMDS as surface treatments suitable for Ta2O5 gate insulator, to improve the characteristics. The OTFT showed a good carrier mobility of 0.3 cm2/Vs, a high current on/off ratio of over 106 and a low operating drain voltage of -6V. We also successively confirmed display operation of the fabricated 16×16 PDLC display panel with a low driving voltage of 13 volts.