Title :
Amorphous silicon thin film transistor circuit integration for organic LED displays on glass and plastic
Author :
Nathan, Arokia ; Kumar, Anil ; Sakariya, Kapil ; Servati, Peyman ; Sambandan, Sanjiv ; Striakhilev, Denis
Author_Institution :
Dept. of Electr. & Comput. Eng., Univ. of Waterloo, Ont., Canada
Abstract :
This paper presents design considerations along with measurement results pertinent to hydrogenated amorphous silicon (a-Si:H) thin film transistor (TFT) drive circuits for active matrix organic light emitting diode (AMOLED) displays. We describe both pixel architectures and TFT circuit topologies that are amenable for vertically integrated, high aperture ratio pixels. Here, the OLED layer is integrated directly above the TFT circuit layer, to provide an active pixel area that is at least 90% of the total pixel area with an aperture ratio that remains virtually independent of scaling. Both voltage-programmed and current-programmed drive circuits are considered. The latter provides compensation for shifts in device characteristics due to metastable shifts in the threshold voltage of the TFT. Various drive circuits on glass and plastic were fabricated and tested. Integration of on-panel gate drivers is also discussed where we present the architecture of an a-Si:H based gate de-multiplexer that is threshold voltage shift invariant. In addition, a programmable current mirror with good linearity and stability is presented. Programmable current sources are an essential requirement in the design of source driver output stages.
Keywords :
amorphous semiconductors; driver circuits; elemental semiconductors; organic light emitting diodes; silicon; thin film transistors; Si:H; TFT circuit; active matrix display; active pixel area; current-programmed drive circuits; organic LED displays; organic light emitting diode; pixel architectures; programmable current sources; thin film transistor; threshold voltage shift invariant; voltage-programmed drive circuits; Active matrix organic light emitting diodes; Amorphous silicon; Apertures; Circuits; Flat panel displays; Glass; Light emitting diodes; Plastics; Thin film transistors; Threshold voltage; Active matrix display; amorphous silicon; organic light emitting diode; thin film transistor;
Journal_Title :
Solid-State Circuits, IEEE Journal of
DOI :
10.1109/JSSC.2004.829373