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The 14.6‐inch 202‐ppi rollable micro LED display was fabricated on flexible LTPS TFT backplanes. The tiny micro LEDs, those size are less than 30 um, were bonded on backplanes by flip‐chip soldering technologies. More than 11 million micro LEDs were transferred to achieve brightness of >1000 nits, contrast ratio of >1,000,000:1 and resolution of 2560xRGBx1440. We investigated the structure and mechanism to achieve the rollable capability for micro LED displays. [ABSTRACT FROM AUTHOR]

A flexible PI‐less micro‐LED display, 228 PPI, has been achieved by transferring the display devices from rigid glass to plastic. By forming this micro‐LED display on a mold with round edge and lowering the edge radius to 100um, a more cubic waterfall display is realized. [ABSTRACT FROM AUTHOR]

9.4‐inch 228‐ppi full‐color micro LED display using the flexible LTPS‐TFT backplane has been successfully developed. In order to solve the interconnection of tiny micro LEDs, those size are less than 30um, we introduced the flip‐chip soldering technology for high resolution flexible micro LED displays. Contrast ratio of >1,000,000: 1 with brightness of 700 nits was realized by the full‐color micro LED display with uniform brightness and color shift free at any off‐axis viewing angles. These supreme micro LED visual performances will be provided more comfortable user experience for high resolution flexible automotive applications. [ABSTRACT FROM AUTHOR]

A 9.4‐inch 228‐ppi full‐color micro‐LED display using the flexible low temperature polysilicon thin‐film transistor (LTPS‐TFT) backplane has been successfully developed. In order to solve the interconnection of tiny micro‐LEDs, those size are less than 30 μm, we introduced the flip‐chip soldering technology for high‐resolution flexible micro‐LED displays. Contrast ratio of >1,000,000:1 with a brightness of 700 nits was realized by the full‐color micro‐LED display with uniform brightness and color shift free at any off‐axis viewing angles. These supreme micro‐LED visual performances will provide a more comfortable user experience for high‐resolution flexible automotive applications. [ABSTRACT FROM AUTHOR]

Thickness of buffer layers affects performance of flexible polycrystalline silicon thin film transistors (TFT). A thicker buffer SiO2 film demonstrates better endurance to thermal expansion stress from the polyimide substrate. However, the thickness of buffer SiO2 film would causes the variation of optimal excimer laser annealing (ELA) crystallization condition. In addition, the simulation results shows that the non-uniform stress in the gate insulator is more pronounced near the poly-silicon/gate insulator edge and at the two sides of the poly-silicon protrusion. It would affect the stability results and device performance. By optimization the process condition, the device would still have good device performance after operating under high temperature (60 □) and long period of time (500hrs). [ABSTRACT FROM AUTHOR]

A highly reliable ultra-high gas barrier (UGB) was developed and applied on the fabrication of 4.3-inch flexible AMOLED. The water vapor transmission rate of the UGB on flexible substrate could achieve ∼ 10−6 g/m2-day under a calcium test (60°C and 90%RH). In addition, a delamination method to remove the flexible AMOLED from the glass carrier was proposed where the mechanical strain during the delamination is controlled within 0.2%. With the incorporation of a metallic interlayer, the damage of TFT due to the electrostatic discharges from the delaminated surfaces can be prevented. [ABSTRACT FROM AUTHOR]

Developments of backplane technologies, which are one of the challenging topics, toward the realization of flexible active matrix organic light-emitting diodes (AMOLEDs) are discussed in this paper. Plastic substrates including polyimide are considered as a good candidate for substrates of flexible AMOLEDs. The fabrication process flows based on plastic substrates are explained. Limited by the temperature that plastic substrates can sustain, TFT technologies with maximum processing temperature below 400 °C must be developed. Considering the stringent requirements of AMOLEDs, both oxide thin-film transistors (TFTs) and ultra-low-temperature poly-silicon TFTs (U-LTPS TFTs) are investigated. First, oxide TFTs with representative indium gallium zinc oxide channel layer are fabricated on polyimide substrates. The threshold voltage shifts under bias stress and under bending test are small. Thus, a 4.0-in. flexible AMOLED is demonstrated with indium gallium zinc oxide TFTs, showing good panel performance and flexibility. Further, the oxide TFTs based on indium tin zinc oxide channel layer with high mobility and good stability are discussed. The mobility can be higher than 20 cm2/Vs, and threshold voltage shifts under both voltage stress and current stress are almost negligible, proving the potential of oxide TFT technology. On the other hand, the U-LTPS TFTs are also developed. It is confirmed that dehydrogenation and dopant activation can be effectively performed at a temperature within 400 °C. The performance of U-LTPS TFTs on polyimide is compatible to those of TFTs on glass. Also, the performance of devices on polyimide can be kept intact after devices de-bonded from glass carrier. Finally, a 4.3-in. flexible AMOLED is also demonstrated with U-LTPS TFTs. [ABSTRACT FROM AUTHOR]