Functional Pixel Circuits for Elastic AMOLED Displays

TitleFunctional Pixel Circuits for Elastic AMOLED Displays
Publication TypeJournal Article
Year of Publication2005
AuthorsServati, P., and A. Nathan
JournalProceedings of the IEEE
Pagination1257 -1264
Date Publishedjul.
Keywordsactive matrix organic LED display, AMOLED display, amorphous semiconductors, amorphous silicon, bending, bending stress orientation, current mirror, elemental semiconductors, flexible displays, LED displays, mechanical stress, organic light emitting diodes, pixel circuit, plastic substrate, plastics, silicon, strain gauges, strain-induced shifts, stress effects, substrate bending, TFT circuit, thin film circuits, thin film transistors, thin-film transistor, threshold voltage shift

While fabrication of active matrix organic LED (AMOLED) displays on plastic substrates continues to face technological challenges, stable electrical operation of thin-film transistor (TFT) pixel circuits under mechanical stress induced by substrate bending remains a critical issue. This paper investigates strain-induced shifts in hydrogenated amorphous silicon TFT characteristics and the compound impact on TFT circuit behavior. Measurements show that the magnitude of the shifts is determined by the direction of current flow in the TFT with respect to the bending stress orientation as well as bias conditions. Physically based compact models are developed that relate device characteristics to material behavior for design and optimization of AMOLED pixel circuits that can maintain immunity to bending stress. In particular, current mirror-based pixel circuits are presented that compensate for the long term threshold voltage shift and instantaneous strain-induced shifts in device characteristics.


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