Kamala Rajan

High operational stability of electrophosphorescent devices

Electrophosphorescent devices with fac-tris(2-phenylpyridine)iridium as the green emitting dopant have been fabricated with a variety of hole and exciton blocking materials. A device with aluminum(III)bis(2-methyl-8-quinolinato)4-phenylphenolate (BAlq) demonstrates an efficiency of 19 cd/A with a projected operational lifetime of 10 000 h, operated at an initial brightness of 500 cd/m2; or 50 000 h normalized to 100 cd/m2. An orange-red electrophosphorescent device with iridium(III) bis(2-phenylquinolyl-N,C2′)acetylacetonate as the dopant emitter and BAlq as the hole blocker demonstrates a maximum efficiency of 17.6 cd/A with a projected operational lifetime of 5000 h at an initial brightness of 300 cd/m2; or 15 000 h normalized to 100 cd/m2. The average voltage increase for both devices is <0.3 mV/h. The device operational lifetime is found to be inversely proportional to the initial brightness, typical of fluorescent organic light emitting devices.

Organic light-emitting devices with extended operating lifetimes on plastic substrates

We fabricate long-lived organic light-emitting devices using a 175 μm thick polyethylene terephthalate substrate coated with an organic–inorganic multilayered barrier film and compare the rate of degradation to glass-based devices. The observed permeation rate of water vapor through the plastic substrate was estimated to be 2×10−6 g/m2/day. Driven at 2.5 mA/cm2, we measure a device lifetime of 3800 h from an initial luminance of 425 cd/m2.

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.

Reliability of Active-Matrix Organic Light-Emitting-Diode Arrays With Amorphous Silicon Thin-Film Transistor Backplanes on Clear Plastic

We have fabricated active-matrix organic light emitting diode (AMOLED) test arrays on an optically clear high-temperature flexible plastic substrate at process temperatures as high as 285 degC using amorphous silicon thin-film transistors (a-Si TFTs). The substrate transparency allows for the operation of AMOLED pixels as bottom-emission devices, and the improved stability of the a-Si TFTs processed at higher temperatures significantly improves the reliability of the light emission over time.

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.

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.

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.