Ruiqing Ma

A single-layer permeation barrier for organic light-emitting displays

Films of a hybrid material with part-SiO2 part-silicone character are deposited as environmental barriers on bottom-emitting and on transparent organic light-emitting diodes. Devices coated with this barrier have lifetimes of up to ∼7500h when stored at 65°C and 85% relative humidity, by far exceeding the industrial requirement of 1000h. The intensity of the Si–O–Si absorption at the wavenumber of 1075cm−1, the wetting angle by water, and the indentation hardness support the interpretation of a homogeneous material with the properties of a SiO2-silicone hybrid. The films remain intact over 58600cycles of bending to ∼0.2% tensile strain.

Phosphorescent organic light-emitting diodes for high-efficacy long-lifetime solid-state lighting

We report data for a pair of singlestack all-phosphorescent 15 × 15 cm 2 organic light emitting-diode (OLED) light panels with high efficacy, long lifetime, and very low operating temperature: Panel 1 has 62 lm∕W efficacy, CRI ¼ 81 and lifetime to LT70 ¼ 18;000 h at 1000 cd∕m 2 , while Panel 2 has 58 lm∕W efficacy, CRI ¼ 82 and lifetime to LT70 ¼ 30;000 h at 1000 cd∕m 2 . Operating at a higher luminance of 3000 cd∕m 2 , Panel 2 has 49 lm∕W efficacy with lifetime to LT70 ¼ 4000 h. Excellent panel lifetime is enabled by a stable light blue phosphorescent materials system. Panel temperatures are within 10°C of ambient temperature at 3000 cd∕m 2 . Panel 2 was further used as a building block to demonstrate an all-phosphorescent OLED luminaire for under-cabinet lighting applications. Operating at approximately 3000 cd∕m 2 , theluminairedelivers570lmwith52 lm∕Wtotalsystemefficacy,CRI ¼ 86andCCT ¼ 2940 K.© 2012 Society of Photo-Optical Instrumentation Engineers (SPIE). (DOI: 10.1117/1.JPE.2.021205)

Flexible active-matrix OLED displays: Challenges and progress

Abstract— Organic light-emitting-device (OLED) devices are very promising candidates for flexible-display applications because of their organic thin-film configuration and excellent optical and video performance. Recent progress of flexible-OLED technologies for high-performance full-color active-matrix OLED (AMOLED) displays will be presented and future challenges will be discussed. Specific focus is placed on technology components, including high-efficiency phosphorescent OLED technology, substrates and backplanes for flexible displays, transparent compound cathode technology, conformal packaging, and the flexibility testing of these devices. Finally, the latest prototype in collaboration with LG. Phillips LCD, a flexible 4-in. QVGA full-color AMOLED built on amorphous-silicon backplane, will be described.

52.4: Highly Efficient Phosphorescent OLED Lighting Panels for Solid State Lighting

We present a 15 cm × 15 cm PHOLEDTM lighting panel that operates with 50 lm/W efficacy, CRI = 87, CCT = 3055 K and lifetime to LT70 ≅ 10,000 hrs at 1,000 cd/m2. We also present a panel with 58 lm/W efficacy, CRI = 86 and CCT = 2790 K at 1,000 cd/m2, and a small-area lighting pixel with 109 lm/W efficacy, CRI = 80, CCT = 3295 K and lifetime to LT70 ≅ 15,000 hrs at 1,000 cd/m2. A highly stable light blue phosphorescent host-emitter system is used to reduce power consumption, extend operational lifetime and demonstrate exceptional emission color stability with aging.

Diffusion of atmospheric gases into barrier-layer sealed organic light emitting diodes

Organic light emitting diodes (OLEDs) are protected from the atmosphere with a barrier layer. Even when this permeation barrier is hermetic, dark spots still may grow and dark sheets may extend into the OLED. These grow by diffusion from the atmosphere along the interfaces between the barrier layer with embedded particles or with the substrate. Observed growth rates of dark spots and sheets are modeled by a single diffusion mechanism. Similar normalized flux densities along the two pathways and a diffusion coefficient of ∼10−8 cm2/s suggest a similar polymeric structure of the barrier/particle and barrier/substrate interfaces.

Wearable 4‐in. QVGA full‐color‐video flexible AMOLEDs for rugged applications

— Work on the worlds first wrist-worn communications device built on a flexible, low-power-consumption full-color AMOLED using phosphorescent OLEDs is presented. The device offers the wearer the ability to see high-information-content video-rate information in a thin-and-rugged-form-factor 4-in. QVGA display, conformed around a human wrist.

65.4: Active Matrix PHOLED Displays on Temporary Bonded Polyethylene Naphthalate Substrates with 180 °C a-Si:H TFTs

A low temperature, 180 °C, amorphous Si (a-Si:H) process on bonded polyethylene naphthalate substrates is discussed and a 4.1-inch QVGA active matrix (AM) phosphorescent OLED display is demonstrated. The n-channel thin-film transistors (TFTs) exhibited saturation mobilities of 0.773 cm2/V-sec, layer to layer registration distortion less than 10ppm and low defectivity. The efficiency of the OLED display is 39 cd/A at 500 nits.

72.2: Phosphorescent OLEDs: Enabling Solid State Lighting with Lower Temperature and Longer Lifetime

We present a pair of 15 cm × 15 cm all-phosphorescent OLED light panels with high efficacy and extended operational lifetime. Panel 1 operates at 1,000 cd/m2 with power efficacy = 62 lm/W. At a higher luminance of 3,000 cd/m2, power efficacy = 49 lm/W, CRI = 82, CCT = 2,950 K and CIE 1931 (x, y) = (0.446, 0.417). Similar high efficacy performance is recorded for Panel 2, which has lifetime to LT70 ∼ 4,000 hrs at 3,000 cd/m2. Excellent lifetime is enabled by a new light blue phosphorescent materials system and by the use of efficient phosphorescent emitters that ensure very low panel temperature without any additional thermal management.

Diffusion of water into permeation barrier layers

Organic light emitting diodes (OLEDs) are attractive candidates for flexible display and lighting panels due to their high contrast ratio. However, the materials in an OLED are oxidized by very small quantities of moisture. Therefore, flexible OLEDs require flexible, thin-film, encapsulation. The authors introduce a set of three techniques for measuring the solubility and diffusion coefficient of water in a permeation barrier layer that is a SiO2-silicone hybrid made by plasma enhanced chemical vapor deposition. The techniques are secondary ion mass spectrometry, and measurements of electrical capacitance and of film stress. The measurements were carried out on samples exposed to water or steam at temperatures between 65 and 200 °C. From the resulting values of water solubility, diffusion coefficient, and their thermal activation energies, the authors calculate the time one monolayer of water will take to permeate through the bulk of the film. For a 3 μm thick film held at 38 °C and 90% relative humidity, the time is 13 years.

43.3: Power Efficient AMOLED Display with Novel Four Sub-Pixel Architecture and Driving Scheme

We present a novel all-phosphorescent AMOLED pixel architecture with a red, green, light blue and deep blue sub-pixel design. The highly efficient light blue reduces power consumption by 33% compared to an equivalent conventional RGB display using a fluorescent blue sub-pixel. Furthermore, by using a light and deep blue sub-pixel layout, the lifetime of the display will be significantly increased due to the reduced on-time required for the deep blue sub-pixel. Here we demonstrate this new design in a 2.5-inch AMOLED panel.