Jeffrey P. Spindler

Triplet annihilation exceeding spin statistical limit in highly efficient fluorescent organic light-emitting diodes

We have demonstrated that the exemplary red fluorescent organic light-emitting diodes (OLEDs) gain as much as half of their electroluminescence from annihilation of triplet states generated by recombining charge carriers. The magnitude of triplet-triplet annihilation (TTA) contribution in combination with the remarkably high total efficiencies [>11% external quantum efficiency (EQE)] indicates that the absolute amount of electroluminescence attributable to TTA substantially exceeds the limit imposed by spin statistics, which was independently confirmed by studying magnetic field effects on delayed luminescence. We determined the value of 1.3 for the ratio of the rate constants of singlet and triplet channels of annihilation, which is indeed substantially higher than the value of 0.33 expected for a purely statistical annihilation process. It is, however, in an excellent quantitative agreement with the extent of the experimental contribution of delayed luminescence to steady-state electroluminescence. The ...

System considerations for RGBW OLED displays

Abstract— The fabrication of full-color RGBW OLED displays using a white emitter with RGB color filters has been previously described. This paper discusses the effect of several display-system factors on the important RGBW OLED display performance attributes of power consumption, lifetime, and perceived image quality. These display-system factors include the spectrum of the white OLED, the white OLED structure, the color-filter selection, the subpixel aperture ratios, and the pixel arrangement (including sub-sampling).

4.3: Lifetime- and Power-Enhanced RGBW Displays Based on White OLEDs

In this paper, we describe techniques for improving the power consumption and lifetime of full-color AMOLED displays with an RGBW pixel format. A highly efficient and stable white OLED, with color optimized for the display white point (D65) has been developed, which enables low power consumption as well as stable emission. Additionally, a novel approach for improving the lifetime of RGBW displays using subsampled R and B subpixels is discussed.

Full-color AMOLED with RGBW pixel pattern

Abstract— A full-color AMOLED display with an RGBW color filter pattern has been fabricated. Displays with this format require about one-half the power of analogous RGB displays. RGBW and RGB 2.16-in.-diagonal displays with average power consumptions of 180 and 340 mW, respectively, were characterized for a set of standard digital still camera images at a luminance of 100 cd/m2. In both cases, a white-emitting AMOLED was used as the light source, and standard LCD filters were used to provide the R, G, and B emission. The color gamuts of these displays were identical and the higher overall efficiency of the RGBW format results from two factors. First, a large fraction of a typical image is near neutral in color and can be reproduced using the white sub-pixel. Second, the white sub-pixel in an RGBW AMOLED display is highly efficient because of the absence of any color filter. The efficiency of these displays can be further enhanced by choosing a white emitter optimized to the target display white point (in this case D65). A two-emission layer configuration based upon separate yellow and blue-emitting regions is shown to be well suited for both the RGBW and RGB formats.

8.2: Development of Tandem White Architecture for Large‐Sized AMOLED Displays with Wide Color Gamut

In this paper, we discuss the development of tandem white OLED structures optimized for TV-Sized full-color AMOLED displays using an RGBW pixel format. A highly efficient (24 cd/A) and stable tandem white OLED, with color optimized for the display white point (D65), has been developed that enables low power consumption ( 100K h). Additionally, we describe the development of new color filters that deliver 102% NTSC ratio when combined with the tandem white OLEDs.

System design for a wide‐color‐gamut TV‐sized AMOLED display

Abstract— By using current technology, it is possible to design and fabricate performance-competitive TV-sized AMOLED displays. In this paper, the system design considerations are described that lead to the selection of the device architecture (including a stacked white OLED-emitting unit), the backplane technology [an amorphous Si (a-Si) backplane with compensation for TFT degradation], and module design (for long life and low cost). The resulting AMOLED displays will meet performance and lifetime requirements, and will be manufacturing cost-competitive for TV applications. A high-performance 14-in. AMOLED display was fabricated by using an in-line OLED deposition machine to demonstrate some of these approaches. The chosen OLED technologies are scalable to larger glass substrate sizes compatible with existing a-Si backplane fabs.

52.2: Hybrid Tandem White OLEDs with High Efficiency and Long Life‐time for AMOLED Displays and Solid‐State Lighting

Excellent performance (61 cd/A efficiency, 27% EQE, 6.2 V, 6500 K white point, 35,000 h half-life) was obtained using 2-stack hybrid tandem white OLED. This is >70% EQE improvement over the all-fluorescent tandem white resulting in >30% reduction in power consumption for a 32″ AMOLED HDTV. Hybrid Tandems for lighting show EQE between 28.4 and − 30.6%, and lifetime between 70,000 and 125,000 h without outcoupling.

70.2: Low‐Voltage White Tandem Structures for Fabricating RGBW AMOLED Displays

We recently demonstrated full-color RGBW AMOLED displays based on white-emitting OLED structures optimized for a D65 white point. The efficiency of the white formulation has been improved by the use of tandem structures with two or three lowvoltage white-emitting units connected by organic “PN”-type connectors. It has been found that the separation between emitting units is critical to the efficiency and the white point of the tandem structure. Optimized two- and three-EL unit structures exhibit efficiencies of 17.4 cd/A and 24.6 cd/A, respectively, compared to 10.7 cd/A for the single-EL unit control. The tandem structures demonstrate excellent operational stability, with extrapolated half-life times for one-, two-, and three-unit test devices of about 50,000 h, 70,000 h, and 110,000 h, respectively, at 1000 cd/m2. We have also fabricated advanced white tandem structures where the color gamut (NTSC x,y ratio) has been improved to greater than 70% using standard color filters.

30.3: White Fluorescent PIN OLED with High Efficiency and Lifetime for Display Applications

Highly efficient and stable white PIN OLED structures based on Kodaks proprietary emitters and Novaleds proprietary p- and n-type dopants have been developed with a focus on AMOLED display applications. At color coordinates of 0.33/0.36, a current efficiency of 15.1 cd/A at a voltage of 3.0 V was achieved at 1000 cd/m2 brightness. The lifetime of this device is 27,000 hours at a starting luminance of 1000 cd/m2. The spectrum of the devices contains a contribution from four emitters (RGBY) and the emission of the presented OLED structures is therefore ideally suited for use in RGBW AMOLED displays. with variations of the blocking layers, the device efficiency can be increased to 16.8 cd/A, which corresponds to an external quantum efficiency of 7.3%. The results in this paper are based on a joint research effort between Eastman Kodak Company and Novaled.

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.