Julia J. Brown

High-efficiency top-emitting organic light-emitting devices

Based on theoretical arguments that top-emitting organic light-emitting devices (TOLEDs) can be more efficient than equivalent bottom-emitting devices, we fabricated TOLEDs comprising reflective anodes and transparent compound cathodes that emit 20.8% more photons in the forward 120° cone than equivalent bottom-emitting OLEDs. Device optimization by tuning the thickness of the top indium–tin–oxide layer according to a microcavity model is also reported.

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.

4.3: A Phosphorescent Active-Matrix OLED Display Driven by Amorphous Silicon Backplane

We have successfully demonstrated a 4.0 inch full-color active matrix OLED display based on amorphous Si a-Si TFT, and incorporating high efficiency phosphorescent materials. The use of a red phosphorescent sub-pixel reduced display power consumption by 42%, compared to a comparable display based on only fluorescent materials This demonstration clearly shows the possibility of using a-Si TFT as driving backplanes for the manufacture of full color AMOLEDs

Recent advances in phosphorescent OLEDs for small‐ and large‐area‐display sizes

— State-of-the-art phosphorescent organic light-emitting diode (PHOLED™) lifetime and efficiency performances for a range of emission colors are reported. Lifetimes in excess of 100,000 hours were demonstrated at display luminance levels for yellow-green and NTSC deep-red emission. In addition, external quantum efficiencies close to the theoretical maximum are demonstrated for long-lived PHOLEDs.

11.1: Invited Paper: Advances in Blue Phosphorescent Organic Light-Emitting Devices

paper discusses the latest developments towards a commercial blue phosphorescent organic light emitting device (PHOLED™) technology. Progress towards achieving a high efficiency, long-lived saturated blue PHOLED is discussed. First, a high efficiency (20% EQE, 45 cd/A), light blue (0.17, 0.39) PHOLED is presented. Next, long-lived blue PHOLEDs having chromaticity co-ordinates (0.17, 0.38) and (0.16, 0.29) are estimated to degrade to half their initial luminance of 200cd/m 2 after >100,000 hrs and 17,500 hrs, respectively. Finally, results from PHOLEDs designed to increase blue color saturation and lifetime are presented. 1. Introductiont organic light emitting devices (PHOLEDs) (1), the singlet excited state (S1) excitons may be converted into the triplet excited state (T1) through inter-system crossing via the presence of a heavy metal atom. In these devices, the triplet states can emit radiatively (T1 to S0), enabling record high conversion efficiencies. The first generation of PHOLEDs contained platinum 2,3,7,8,12,13,17,18-octaethyl-12H,23H-porphyrin (PtOEP) as the dopant phosphor. An impressive external quantum efficiency, at the time, of 6% was reported (2).

Status and potential for phosphorescent OLED technology

As organic light emitting device (OLED) technology is building up momentum in the commercial marketplace, phosphorescent OLEDs (PHOLEDsTM) are proving themselves to be an ideal display medium for a wide range of product applications: from small mobile displays to large area TVs. As part of this work we continue to advance PHOLED technology by new materials design and device architectures. For example a green PHOLED with 4.3 V, 70 cd/A, 50 lm/W and > 10,000 hours lifetime at 1,000 cd/m2 is reported. PHOLEDs enable very low power consumption displays with low display operating temperatures, and can be deposited by a range of different deposition techniques. Along with state-of-the-art device performance we report results on the ruggedness of PHOLED materials in high volume manufacturing environments.

High‐efficiency phosphorescent OLED technology

Universal Display Corp. (UDC), together with its academic partners at Princeton University and the University of Southern California, are developing high-efficiency electrophosphorescent small-molecule OLED devices, based on triplet emission. These device systems show good lifetimes, and are well suited for the commercialization of low-power-consumption full-color active-matrix OLED displays. In this paper we also show how these phosphorescent devices may be driven by low-cost amorphous-silicon backplanes, and discuss benefits that could be gained by employing bistable OLED pixels.

Active‐matrix technology for high‐efficiency OLED displays

Organic light-emitting device (OLED) technology has recently been shown to demonstrate excellent performance and cost characteristics for use in numerous flat-panel-display (FPD) applications. Universal Display Corp. (UDC), together with its academic partners at Princeton University and the University of Southern California, are developing high-efficiency electrophosphorescent OLEDs, based on triplet emission. These material systems show good lifetimes, and are well suited for the commercialization of low-power-consumption full-color active-matrix OLED displays. Their very high conversion efficiencies may even allow them to be driven by amorphous-silicon backplanes, and in this paper we consider design guidelines for an amorphous-silicon pixel to minimize display non-uniformities due to threshold voltage variations.

Optimization of Reliable Transparent Organic Light‐Emitting Devices

The optical and electrical properties of the Mg-Ag/ITO electrode of transparent organic light emitting devices (TOLED) have been extensively studied. An optimum thickness of Mg-Ag has been chosen to achieve low operational voltage and high transparency. A more than 20-fold improvement in ITO deposition rate over that previously reported has been achieved. Reliability data comparable to those of conventional OLEDs have been obtained.