Flexible active matrix displays and integrated amorphous silicon source drivers

In the last few years there has been an enormous growth in the number of portable devices such as cell phones, notebook PCs, palm-top computers, mp3 players, etc. All these devices have liquid crystal displays (LCD) which are heavy, fragile and power hungry. There is significant interest in developing light weight, rugged, flexible displays on stainless steel and plastic substrates. The display technologies considered in this thesis are electrophoretic, cholesteric and organic light emitting diodes (OLED) using amorphous silicon (a-Si:H) thin film transistor (TFT) backplanes. These displays need external drivers which are bonded to the active matrix backplane using tape automated bonding (TAB) which tend to reduce reliability. One way to improve the reliability and reduce cost is to integrate the source and gate drivers on the active matrix backplane using a-Si:H TFTs.; In this thesis, amorphous silicon active matrix backplanes for electrophoretic, cholesteric and OLED flexible displays are developed and integrated source drivers for electrophoretic displays are demonstrated. A 4" quarter video graphics array (QVGA) a-Si:H TFT backplane with 240 x 320 pixels for electrophoretic displays has been designed, fabricated and successfully tested on heat stabilized Polyethylene Naphthalate (PEN) and thin stainless steel substrates. A 64x64 active matrix backplane for cholesteric display on silicon substrate and OLED on PEN substrate are also demonstrated. In order to reduce the number of external interconnects, source driver architectures to drive 4" QVGA electrophoretic displays have been developed. A single column of the source driver was fabricated using amorphous silicon TFT technology and tested at up to 30Hz frame rate. The current design reduces the number of column interconnects of a 4" QVGA display by more than 3x compared to a display with external drivers. An 8x8 active matrix backplane for an electrophoretic display with integrated source drivers was fabricated and successfully tested with image data. Also, the effect of threshold voltage shift due to stress/rest combination on the output voltage of inverters and latches was determined.