Amorphous silicon thin film transistor circuit integration for organic LED displays on glass and plastic

TitleAmorphous silicon thin film transistor circuit integration for organic LED displays on glass and plastic
Publication TypeJournal Article
Year of Publication2004
AuthorsNathan, A., A. Kumar, K. Sakariya, P. Servati, S. Sambandan, and D. Striakhilev
JournalSolid-State Circuits, IEEE Journal of
Pagination1477 - 1486
Date Publishedsep.
Keywordsactive matrix display, active pixel area, amorphous semiconductors, current-programmed drive circuits, driver circuits, elemental semiconductors, organic LED displays, organic light emitting diode, organic light emitting diodes, pixel architectures, programmable current sources, Si:H, silicon, TFT circuit, thin film transistor, thin film transistors, threshold voltage shift invariant, voltage-programmed drive circuits

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.


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