Richard Hewitt

Thin film encapsulated flexible organic electroluminescent displays

We describe encapsulated passive matrix, video rate organic light-emitting diode (OLED) displays on flexible plastic substrates using a multilayer barrier encapsulation technology. The flexible OLED (FOLED™) displays are based on highly efficient electrophosphorescent OLED (PHOLED™) technology deposited on barrier coated plastic (Flexible Glass™ substrate) and are hermetically sealed with an optically transmissive multilayer barrier coating (Barix™ encapsulation). Preliminary lifetime to half initial luminance (L0∼100 cd/m2) of order 200 h is achieved on the passive matrix driven encapsulated 80 dpi displays; 2500 h lifetime is achieved on a dc tested encapsulated 5 mm2 FOLED test pixel. The encapsulated displays are flexed 1000 times around a 1 in. diameter cylinder and show minimal damage.

Power Consumption and Temperature Increase in Large Area Active-Matrix OLED Displays

We model and analyze the power consumption and resulting temperature rise in active-matrix organic-light-emitting device (AMOLED) displays as a function of the OLED efficiency, display resolution and display size. Power consumption is a critical issue for mobile display applications as it directly impacts battery requirements, and it is also very important for large area applications where it affects the display temperature rise, which directly impacts the panel lifetime. Phosphorescent OLEDs (PHOLEDs) are shown to offer significant advantage as compared to conventional fluorescent OLEDs due to high luminous efficiency resulting in lower pixel currents, reducing both the power consumed in the OLED devices and the series connected driving thin-film transistor (TFT). The power consumption and temperature rise of OLED displays are calculated as a function of the device efficiency, display size, display luminance and the type of backplane technology employed. The impact of using top-emission OLEDs is also discussed.

Performance of high‐efficiency AMOLED displays

In this paper, the performance of active-matrix-driven small-molecule OLED displays incorporating high-efficiency electrophosphorescent dopants were analyzed. These enable triplet excitons to contribute to light emission and have led to pixel efficiencies of over 40 lm/W. By considering a conventional two TFT per pixel addressing scheme, we show how this OLED design enables the fabrication of very-low-power-consumption displays (lower than AMLCDs). We simulate display performance and perform a trade-off analysis comparing the power consumption of displays driven by both amorphous-silicon and low-temperature poly-Si TFTs.

64.2: Full Color 100 dpi AMOLED Displays on Flexible Stainless Steel Substrates

We demonstrate full color, top emission, active matrix OLED displays on flexible stainless steel substrates. The 100 dpi QVGA displays are driven by LTPS TFT backplane with excimer laser annealed poly-Si. To our knowledge this is the worlds highest resolution full color flexible AMOLED display on steel foil demonstrated to date. Encapsulation is by a multilayer thin film.

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.

21.4: Thin Film Encapsulated Flexible OLED Displays

Fully encapsulated passive matrix, video rate, phosphorescent OLED displays on flexible plastic substrates using a multilayer barrier encapsulation technology are described. The flexible OLED (FOLED™) displays are based on highly efficient electrophosphorescent OLED (PHOLED™) technology deposited on barrier coated plastic film (Flexible Glass™ substrate) and are hermetically sealed with an optically transmissive multilayer barrier coating (Barix™ Encapsulation). Preliminary lifetime to half initial luminance (Lo∼100 cd/m2) of order 200 h is achieved on the encapsulated 80 dpi displays using a passive matrix drive at room temperature; 2500 h lifetime is achieved on a dc tested encapsulated 5 mm2 FOLED test pixel. The encapsulated displays are flexed 1000 times around a 1″ diameter cylinder and show minimal damage.

49.3: A 200‐dpi Transparent a‐Si TFT Active‐Matrix Phosphorescent OLED Display

We have fabricated a 120×160 high-resolution (200dpi) a-Si TFT active-matrix transparent phosphorescent OLED (PHOLED™) display with novel pixel architecture to maximize transparency and aperture ratio and also ensure comparable light emission from both sides of the display. The a-Si backplane was selected as the technology that would most easily enable the pathway toward achieving high-resolution flexible transparent AMOLEDs (T-AMOLEDs) on polymeric substrates. A-Si TFTs are preferred for fabrication on polymeric substrates since lower process temperatures can be used in comparison to poly-Si TFT processes. As a TOLED generally emits less light from a transparent cathode than anode, a standard 2T pixel was designed with both an opaque, reflective anode region on top of the TFTs as well as a conventional transparent ITO anode to equal the emission from both contacts. This design achieves a total pixel aperture ratio of 64% with a display transparency of 23% in the off-state.

P-11: Analysis of Low Power Consumption AMOLED Displays on Flexible Stainless Steel Substrates

We present simulations and results to demonstrate the viability of metal foil as a substrate for low power consumption, flexible AMOLED displays. We show that using organic planarization layers, very smooth surface properties can be achieved resulting in excellent TFT performance, and that capacitive coupling effects only have a minimal impact on power consumption, and a small impact on gate line delays. We demonstrate that using phosphorescent OLEDs it is possible to design low power consumption 40″ AMOLED displays.

Flexible phosphorescent OLEDs on metal foil for military and commercial applications

We report recent advances in the development of low power consumption, emissive, flexible active matrix displays through integration of top emitting phosphorescent OLED (T-PHOLED) and poly-Si TFT backplane technologies. The displays are fabricated on flexible stainless steel foil. The T-PHOLEDs are based on UDC phosphorescent OLED technology, and the backplane is based on PARCs Excimer Laser Annealed (ELA) poly-Si TFT process. We also present progress in operational lifetime of encapsulated T-PHOLED pixels on planarized metal foil and discuss PHOLED encapsulation strategy.

White phosphorescent organic light emitting devices for lighting applications

Consumer display manufacturers are increasingly interested in white organic light emitting devices (WOLEDs), because these devices offer thinner display profiles, and in combination with color filters eliminate the need for high-resolution shadow masks. Additionally, WOLEDs are well suited for general-purpose illumination, since the power efficiencies of laboratory devices have surpassed that of todays commercial incandescent bulbs. In this paper, we report on an all phosphorescent 25 cm2 WOLED lighting system that achieves (31±3) lm/W at 850 cd/m2 with CIE coordinates (0.37, 0.36), and an external quantum efficiency of (29±3)%.