Chun- Cheng

High-contrast top-emitting organic light-emitting devices for active-matrix displays

Unlike previous high-contrast devices that all involve inserting extra layer(s) with optical purposes (e.g., absorption and interference) into the active region of devices, in this-letter we report a high-contrast top-emitting organic light-emitting device (OLED) that utilizes only optical characteristics of electrodes and anti-reflection coatings deposited outside the active region, thus reducing the complexity of devices. Furthermore, the device has an inherent microcavity which is beneficial to electroluminescence efficiency. The devices are readily compatible with the processing of active-matrix backplanes, and active-matrix OLED displays incorporating such high-contrast top-emitting devices were demonstrated to have improved readability under a strong lighting environment.

Amorphous InGaZnO Thin-Film Transistors Compatible With Roll-to-Roll Fabrication at Room Temperature

High-performance amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs) are successfully fabricated on a colorless polyimide substrate using a top-gate self-aligned structure. All thin films are deposited by roll-to-roll-compatible sputtering processes at room temperature. The maximum field-effect mobility is 18 cm2/V·s, the threshold voltage is -1.35 V, the subthreshold slope is 0.1 V/decade, and the on/off current ratio is about 105. The results highlight that excellent device performance can be realized in a-IGZO TFTs without compromising manufacturability.

Influence of Passivation Layers on Characteristics of a-InGaZnO Thin-Film Transistors

We investigated the influence of passivation-layer deposition on the characteristics of a-InGaZnO thin-film transistors (TFTs). The threshold voltage (VT) of the TFTs shifted markedly as a result of the mechanical stress induced by the passivation layers above. By adjusting the deposition parameters during the passivation process, the performance of the TFTs can be modulated. The a-InGaZnO TFTs after dual passivation exhibited good performance with a field-effect mobility of 11.35 cm2/V·s, a threshold voltage of 2.86 V, and an on-off ratio of 108.

Effects of Mechanical Strains on the Characteristics of Top-Gate Staggered a-IGZO Thin-Film Transistors Fabricated on Polyimide-Based Nanocomposite Substrates

In this paper, we had successfully implemented flexible top-gate staggered amorphous In-Ga-Zn-O (a-IGZO) thin- film transistors (TFTs) on colorless and transparent polyimide (PI)-based nanocomposite substrates using fully lithographic and etching processes that are compatible with existing TFT mass fabrication technologies. The use of the selectively coated release layer between the nanocomposite PI film and the glass carrier ensured smooth debonding of the plastic substrate after TFT fabrication. The TFTs showed decent performances (with mobility >; 10 cm2/V · s) either as fabricated or as debonded from the carrier glass. By bending the devices to different radii of curvature (from a flat state to an outward bending radius of 5 mm), influences of mechanical strains on the characteristics of flexible a-IGZO TFTs were also investigated. In general, the mobility of the flexible a-IGZO TFT increased with the tensile strain, whereas the threshold voltage decreased with the tensile strain. The variation of the mobility in a-IGZO TFTs versus the strain appeared smaller than those observed for amorphous silicon TFTs.

Top-Gate Staggered a-IGZO TFTs Adopting the Bilayer Gate Insulator for Driving AMOLED

We report the successful implementation of top-gate staggered amorphous In-Ga-Zn-O (a-IGZO) thin-film transistors (TFTs) with decent performance and environmental stability by adopting the SiOx/SiNx bilayer gate-insulator stack. The PECVD SiOx and SiNx were used as the first and second gate insulators, respectively, in the TFT to simultaneously ensure the channel/gate-insulator interface properties for device performances and the water impermeability of the gate insulator for effective passivation of the channel layer. It was also found that the cleanliness of the back-channel interface (and thus the effectiveness of the source/drain etching process) is critical for the successful implementation of the top-gate staggered a-IGZO TFTs. In this paper, a two-step wet-etching process for source/drain was used to ensure the quality of the back-channel interface. Finally, we successfully integrated the top-gate staggered a-IGZO TFTs into a working 2.2-in active matrix organic light-emitting display panel, demonstrating the real use of the developed TFTs.

38.3: LTPS Active Matrix OLED Displays Incorporating High‐Contrast Top‐Emitting OLEDs

A 3.8-inch high-contrast top-emitting AMOLED display using the LTPS TFT backplane is demonstrated. The display incorporates low-reflection top-emitting OLEDs with improved efficiency, and thus exhibits clear readability under a strong lighting environment without need of extra contrast-enhancement films.

22.3: Flexible Top‐gate Amorphous InGaZnO TFTs Array for AMOLED Applications

Flexible top-gate amorphous InGaZnO TFTs array on a colorless polyimide substrate for AMOLED applications was successfully fabricated at 200 °C for the first time. The light transmittance of polyimide substrate is 90%. The maximum field-effect mobility is 10.6 cm2/V-s, subthreshold swing is 0.3 V/decade, and the on/off current ratio is 108.

P‐37: Room Temperature Top‐Gate Self‐Aligned Amorphous InGaZnO TFTs Fabricated on Colorless Polyimide Substrate

Room temperature top-gate self-aligned amorphous InGaZnO TFTs were successfully fabricated on colorless polyimide plastic substrates for the first time. All these thin films were deposited by sputtering system at room temperature. The maximum field-effect mobility is 48.5 cm2/V-s, the subthreshold swing is 0.1 V/decade, and the threshold voltage is −1V.

High-contrast top-emitting OLEDs for OLED displays

This paper describes a top-emitting OLED structure that implements both low ambient light reflection within the OLED structure and reasonable emission efficiency. Ambient light reflection from a top-emitting device can be effectively suppressed by using a moderate bottom reflector and top antireflection coating, meanwhile retaining acceptable EL efficiency and other viewing characteristics for display applications.

Temperature instability of low-temperature deposited a-Si:H TFTs fabricated on plastic substrate

— Low-temperature deposited a-Si:H TFTs have been successfully fabricated on colorless polyimide (CPI) substrate for flexible-display applications. A serious degradation in threshold voltage was observed after applying external thermal stress. The threshold-voltage shift saturates after applying several thermal stress cycles. In addition, the TFTs show instability under long periods of thermal stress with fixed temperature. This phenomenon was composed of thermally induced traps and substrate-expansion-induced mechanical stress. Finally, the a-Si:H TFT backplane fabricated on a PI substrate at low temperature has been successfully demonstrated for flexible AMLCDs.