William James Begley

60.1: Invited Paper: Tandem Hybrid White OLED Devices with Improved Light Extraction

A high-efficacy white OLED device is reported. At 1,000 cd/m2, the device showed an efficacy of 56 lm/W. The color at (0.387, 0.389) was within the Energy Star tolerance quadrangle; the CRI at 83.6 exceeded the requirements. The device had a tandem hybrid architecture comprising a fluorescent blue-emitting unit and a phosphorescent yellow-red-emitting unit. It also had an internal extraction enhancement structure that greatly enhanced the light extraction efficiency.

54.2: Tandem White OLEDs Combining Fluorescent and Phosphorescent Emission

Tandem white OLEDs with fluorescent and phosphorescent emission have been fabricated. Their electroluminescence performance is dependent on fluorescent blue-emitting portion in a white spectrum. When CIEx = 0.33, CIEy = 0.35, the devices can achieve 22% external quantum efficiency, 50 cd/A, 25 lm/W, and ∼10,000 h lifetime, tested at 6.2 V and 1000 nits. If the blue-emitting portion is reduced to produce color with CIEx = 0.34, CIEy = 0.40, the devices can exhibit ∼23% external quantum efficiency, 57 cd/A, 30 lm/W, and ∼30,000 h lifetime when tested at 5.9 V and 1000 nits.

61.2: Fluorescent White OLED Devices with Improved Light Extraction

An all-fluorescent white OLED device with 14.5% external quantum efficiency and 31.2 lm/W efficacy has been demonstrated. The color coordinate at (0.387, 0.381) falls well within the DOE Energy Star tolerance quadrangle for 4000K CCT. The T50 lifetime is projected to be over 10,000 h at an initial brightness of 1,000 cd/m2. The performance is achieved through the use of improved OLED materials, improved architecture, as well as a light extraction structure that more than doubles the light extraction efficiency.

Charge carriers and charge-transfer reactions in OLED devices studied by electron paramagnetic resonance†

Abstract— Electron paramagnetic resonance (EPR) was used as a quantitative method to measure charge carriers that are present in OLED devices under various bias conditions. Charge-transfer reactions that occur at the cathode interface through the interaction of charge-injection layers and charge-transport layers were investigated.

P‐190: Novel Electron‐Transporting Layer for Lowering Drive Voltage and Improving the Efficiency of OLED Devices

We report herein a new electron-transport layer (ETL) that reduces drive voltage, improves external quantum efficiency, and increases device operational stability. This new ETL has worked with red-, blue-, green-, and white-light emitting devices, but it is exceptionally suitable for improving the performance of the red-emitting device. By employing this new ETL, we prepared a fluorescent red device that provides a record luminance efficiency of 9.3 cd/A, an external quantum efficiency of 6.6%, power efficiency of 6.4 lm/W and color coordinates CIEx,y of 0.65 and 0.35, respectively. Compared to the Alq3 reference ETL, the new ETL decreases the drive voltage by 1.2 V, improves the external quantum efficiency by greater than 50%, and gives a three-fold increase in operational stability. To our knowledge, this is the highest performance obtained from a red-emitting fluorescent device. The new ETL reduces display power consumption while simultaneously increasing operational stability.

30.4: High-Efficiency Fluorescent Red- and Yellow-Emitting OLED Devices

We report high-efficiency fluorescent red OLEDs with 11.5% EQE (15 cd/A) at 3 V, and yellow OLEDs with 8.6% EQE (28 cd/A) at 2.9 V. This performance was obtained using a nonemitting assist layer adjacent to the emission layer, and low-voltage electron-transporting and electron-injecting layers. Time-resolved electroluminescence measurements indicate a significant efficiency contribution (up to 50%) from triplet—triplet annihilation processes.

35.3: High‐Performance Tandem White OLEDs Using a Li‐Free “P‐N” Connector

A nonmetallic connector has been developed for high-efficiency tandem white architecture. Forming the “N” type layer using NDN-26 doped into NET-18 and inserting an organometallic thin layer between the “N” and “P” layers results in a high-performance connector. An efficiency of 33 cd/A has been achieved at 6.7 V, 1000 cd/m2 and 10000K color temperature in a fluorescent based tandem emitter. This >15% EQE device also demonstrates a half-life of ∼80,000 h at 1000 cd/m2.

36.2: High-Performing Organic Electron-Injecting and Transporting Layers for Red, Green, Blue, and White OLED Devices

A new electron-injecting layer (EIL) for increasing the efficiency and lowering the power consumption of OLED devices has been developed. The performance of this new EIL, in combination new electron-transporting layers (ETLs), will be discussed. These devices show superior behavior when compared to controls containing the commonly used LiF injecting material or a lithium-doped Alq3: Bphen ETL. At 20 mA/cm2 current density, red device performance is 10.8 cd/A operating at 3.9 V and color CIEx,y = 0.66, 0.34; green performance is 18.4 cd/A at 4.2 V and color CIEx,y = 0.29, 0.62; deep blue performance is 7.7 cd/A at 3.7 V and color CIEx,y = 0.14, 0.13; blue-green performance is 21.1 cd/A at 4.2 V and color CIEx,y = 0.16, 0.37 and a white device is 13.2 cd/A at 3.8 V and color CIEx,y = 0.34, 0.34. At the same operating conditions, the external quantum efficiencies (EQEs) obtained for red, deep blue and blue-green devices were 8.2%, 6.6%, and 9.7% respectively. These are among the highest efficiencies reported so far for singlet emitting devices.

P-169: Efficient, Long-Lifetime OLED Host and Dopant Formulations for Full-Color Displays

We report developments in materials and formulations for blue, green, and red fluorescent OLEDs that provide lifetimes exceeding 15,000 h for a model display operating at 200 cd/m2 with a polarizer. In addition, we describe improvements in electron transport and injection that result in a reduction in display power consumption of up to 55%.

Advanced materials and formulations for OLED display manufacturing

This paper describes Eastman Kodak Companys commercialization efforts to develop new materials and formulations for monochrome and full-color displays. We have found a new set of materials, and combinations thereof, that improve luminance efficiency, lower drive voltage, and increase the operational stability of OLED devices. We report the developments in formulations for blue and white OLEDs based on fluorescent dopants that provide lifetimes exceeding 10,000 hours for blue, and 50,000 hours for white OLEDs at a starting luminance level of 1000 cd/m2. A red formulation, based on a fluorescent dopant using a new host, is shown to give a record luminance efficiency of 7.8 cd/A combined with excellent color and lifetime. We have found a phosphorescent red-emitting device using a novel host material that gives an excellent efficiency of 9.6 lm/W. Further progress has been made in a new electron-transport layer to reduce display drive voltage, and thus reduce power consumption, while simultaneously increasing operational stability. We have compared this performance with currently available systems.