Dong-un Jin

65.2: Distinguished Paper: World-Largest (6.5”) Flexible Full Color Top Emission AMOLED Display on Plastic Film and Its Bending Properties

The world largest flexible full color 6.5-inch active matrix organic light emitting diode (AMOLED) display with top emission mode on plastic film is demonstrated. The active matrix backplanes were fabricated using metal oxide thin film transistors (TFTs). The n-channel metal oxide TFTs on plastic film exhibited field-effect mobility of 17.8 cm2/Vs, threshold voltage of 0.4 V, on/off ratio of 1.1× 108, and subthreshold slope of 0.34 V/dec. These TFT performance characteristics made it possible to integrate scan driver circuit, demux switching and compensation circuit on the panel. Bending tests were performed with TFT backplane samples to determine critical curvature radius to which the panel can be bent without TFT performance degradation. The results were compared with the calculations that took into account thicknesses and mechanical constants of flexible substrate and of thin-film layers in AMOLED device.

Flexible full color organic light-emitting diode display on polyimide plastic substrate driven by amorphous indium gallium zinc oxide thin-film transistors

We have fabricated 6.5 in. flexible full-color top-emission active matrix organic light-emitting diode display on a polyimide (PI) substrate driven amorphous indium gallium zinc oxide thin-film transistors (a-IGZO TFTs). The a-IGZO TFTs exhibited field-effect mobility (μFE) of 15.1 cm2/V s, subthreshold slope of 0.25 V/dec, threshold voltage (VTH) of 0.9 V. The electrical characteristics of TFTs on PI substrate, including a bias-stress instability after 1 h long gate bias at 15 V, were indistinguishable from those on glass substrate and showed high degree of spatial uniformity. TFT samples on 10 μm thick PI substrate withstood bending down to R=3 mm under tension and compression without any performance degradation.

47.2: 2.8‐inch WQVGA Flexible AMOLED Using High Performance Low Temperature Polysilicon TFT on Plastic Substrates

This paper reports a low-temperature polycrystalline silicon (LTPS) fabrication process on plastic substrate for a flexible AMOLED display. Characteristics of fabricated TFTs showed excellent performance with field effect mobility of 124.1 cm2/V-s, on/off ratio of >108, subthreshold slope of 0.30V/dec, and threshold voltage of −2.03V. Internal scan drive circuits, 1:3 demux, and compensation circuits were successfully integrated on the backplane of a 166ppi 2.8″ WQVGA flexible AMOLED panel.

47.1: Invited Paper: Highly Robust Flexible AMOLED Display on Plastic Substrate with New Structure

A new flexible TFT backplane structure with improved mechanical reliability has been fabricated on a plastic substrate using amorphous indium-gallium-zinc-oxide (a-IGZO) thin film transistors. The panel withstood 10,000 bending cycles at a bending radius of 5 mm without any noticeable TFT degradation. After the bending test, change of Vth, mobility, sub-threshold slope, and gate leakage current were only −0.10V, −0.11cm2/V-s, 0.01V/decade, and −1.03×10-−12A, respectively. No line defects, dark spots, or bright spots appeared after 10K bending cycles at a bend radius of 10 mm.

16.2: World-Best Performance LTPS TFTs with Robust Bending Properties on AMOLED Displays

This study reported a low temperature polycrystalline silicon LTPS thin film transistor TFT fabrication process on plastic substrates for flexible display applications. Polycrystalline silicon poly-Si films were formed by excimer laser annealing ELA method. It was found by ELA thermal simulation that there was around 70 □ on plastic surface during ELA crystallization process. The excimer laser irradiated film was analyzed by using various spectroscopic methods such as X-ray diffraction, scanning electron microscopy, and atomic force microscopy. Dehydrogenation and activation processes were performed by a conventional LTPS method without causing any plastic substrate distortion. The fabricated poly-Si TFT on a flexible backplane shows a very good performance with field effect mobility of 95.3 cm2/Vs, on/off ratio current ratio > 108, and threshold voltage of −1.6 V. Bending tests after a delamination process were also performed with TFT backplane samples.

Flexible AMOLED displays on stainless-steel foil

— The worlds thinnest flexible full-color 5.6-in. active-matrix organic-light-emitting-diode (AMOLED) display with a top-emission mode on stainless-steel foil was demonstrated. The stress in the stainless-steel foil during the thermal process was investigated to minimize substrate bending. The p-channel poly-Si TFTs on stainless-steel foil exhibited a field-effectmobility of 71.2 cm2/N-sec, threshold voltage of −2.7 V, off current of 6.7 × 1013 A/μm, and a subthreshold slope of 0.63 V/dec. These TFT performances made it possible to integrate a scan driver circuit on the panel. A top-emission EL structure was used as the display element, and thin-film encapsulation was performed to realize a thin and flexible display. The full-color flexible AMOLED display on stainless-steel foil is promising for mobile applications because of its thin, light, rugged, and flexible properties.