High-efficiency top-emitting organic light-emitting devices

Lu, Min; Weaver, Michael S.; Zhou, Theodore X.; Rothman, M.; Kwong, Raymond C.; Hack, M.; Brown, J.J.

doi:10.1063/1.1523150

Cited by 180 publications

(105 citation statements)

References 14 publications

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“…The methodology for optimizing viewing characteristics of top-emitting OLEDs has been presented [10,11]. In this paper, we have designed a TOLED with a symmetric structure, in which two metal layers was used next to the transparent electrodes and functioned as a hole injection and an electron injection layer, respectively.…”

Section: Introductionmentioning

confidence: 99%

High-efficiency transparent organic light-emitting diode with one thin layer of nickel oxide on a transparent anode for see-through-display application

Wei¹,

Yamamoto²,

Ichikawa³

et al. 2007

Semicond. Sci. Technol.

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Work function of different species of metal oxide has been investigated, and of nickel oxide was found to reach about 5.4 eV, much higher than those of other metal species and indium tin oxide (ITO). The transparent organic light-emitting diode using a thin oxidation of nickel film upon ITO as an anode and a thin MgAg layer as a cathode has been fabricated. Device performance was found to improve greatly due to an efficient hole injection from nickel oxide; moreover, the top-emitting intensity was nearly same as the bottom-emitting intensity of device. The current efficiencies of the bottom and top emissions reached about 4.1 and 3.2 cd/A, respectively.2

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Section: Introductionmentioning

confidence: 99%

High-efficiency transparent organic light-emitting diode with one thin layer of nickel oxide on a transparent anode for see-through-display application

Wei¹,

Yamamoto²,

Ichikawa³

et al. 2007

Semicond. Sci. Technol.

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“…Top-emitting OLEDs have recently been shown to offer an efficient way to generate light. [1][2][3] Most aspects of OLED performance that impinge on device efficiency have now been optimized, but there is still scope for improving light outcoupling. A schematic of the structure we consider is shown in Fig.…”

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confidence: 99%

Light outcoupling efficiency of top-emitting organic light-emitting diodes

Smith

Wasey

Barnes

2004

Applied Physics Letters

194

115

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We report results obtained from modeling the light outcoupling efficiency of top-emitting organic light-emitting diode ͑OLED͒ structures and compare them with results from conventional substrate-emitting structures. We investigate two types of emissive material, small molecule and conjugated polymers, and study three different cathode materials; aluminum, silver, and calcium. We show that top-emitting OLEDs may have outcoupling efficiencies comparable to their substrate-emitting counterparts, and that the choice of cathode material is critical to the optical performance of the device. © 2004 American Institute of Physics. ͓DOI: 10.1063/1.1712036͔Organic light emitting diodes ͑OLEDs͒ are being commercially exploited, owing to the many appealing features they possess, notably the ease with which they may be fabricated. Conventional OLEDs are substrate emitting, with light emitted typically through a glass substrate. For display applications active matrix driven pixels are required and a good way to accomplish this is to make top-emitting OLEDs, i.e., for the emission to take place through the cathode. This would allow OLEDs to be incorporated onto a silicon substrate, thus enabling easier integration of light emitting and control components. Top-emitting OLEDs have recently been shown to offer an efficient way to generate light. 1-3Most aspects of OLED performance that impinge on device efficiency have now been optimized, but there is still scope for improving light outcoupling. A schematic of the structure we consider is shown in Fig. 1͑a͒ with the organic light-emitting layer sandwiched between a reflective anode and a composite metal/indium-tin-oxide ͑ITO͒ cathode. We model the conventional substrate-emitting OLED structure ͓Fig. 1͑b͔͒ for comparison.In order to optimize devices it is important to study the details concerning the amount of power lost to various decay channels. The decay of excitons within the emissive organic layer may result in outcoupled light, in power lost to guided modes, 4 including surface plasmon-polariton ͑SPP͒ modes, 5 or lost as heat to one of the electrodes. SPPs result from the coupling between the free charges at the surface of a metal and electromagnetic radiation. 6 This interaction leads to longitudinal surface charge density fluctuations that propagate along the interface combined with an oscillating EM field that decays exponentially away from the metallic surface.Here we investigate how the position of the emitters within the organic layer changes the strength of the coupling to different modes, and thus the optical efficiency of the device. To do this we make use of a specially adapted classical technique to calculate the power lost by an emissive dipole in a multilayered structure, 7 with the dipole field being represented by a sum of plane waves. Each plane wave is characterized by a different in-plane wave vector, k x , where k x is the component of the wave vector parallel to the interfaces. By calculating the power dissipated by the dipole as a function of k x we are a...

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“…7 The extraction efficiency (or light out-coupling) is especially challenging for bottom emitting devices, where the transparent substrate is coated with the transparent conducting electrode, as this combination can trap internally a high proportion of emitted light due to total internal reflection at the substrateair interface. 8 Top emitting devices usually have higher extraction efficiency 9 but can still trap many of the photons generated in the device. Enhancing light out-coupling is important if OLEDs are to play a significant role in lighting applications.…”

Section: Introductionmentioning

confidence: 99%

AZO/Ag/AZO anode for resonant cavity red, blue, and yellow organic light emitting diodes

Gentle

Yambem

Burn

et al. 2016

Journal of Applied Physics

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Indium tin oxide (ITO) is the transparent electrode of choice for organic light-emitting diodes (OLEDs). Replacing ITO for cost and performance reasons is a major drive across optoelectronics. In this work, we show that changing the transparent electrode on red, blue, and yellow OLEDs from ITO to a multilayer buffered aluminium zinc oxide/silver/aluminium zinc oxide (AZO/Ag/AZO) substantially enhances total output intensity, with better control of colour, its constancy, and intensity over the full exit hemisphere. The thin Ag containing layer induces a resonant cavity optical response of the complete device. This is tuned to the emission spectra of the emissive material while minimizing internally trapped light. A complete set of spectral intensity data is presented across the full exit hemisphere for each electrode type and each OLED colour. Emission zone modelling of output spectra at a wide range of exit angles to the normal was in excellent agreement with the experimental data and hence could, in principle, be used to check and adjust production settings. These multilayer transparent electrodes show significant potential for both eliminating indium from OLEDs and spectrally shaping the emission.

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High-efficiency top-emitting organic light-emitting devices

Cited by 180 publications

References 14 publications

High-efficiency transparent organic light-emitting diode with one thin layer of nickel oxide on a transparent anode for see-through-display application

High-efficiency transparent organic light-emitting diode with one thin layer of nickel oxide on a transparent anode for see-through-display application

Light outcoupling efficiency of top-emitting organic light-emitting diodes

AZO/Ag/AZO anode for resonant cavity red, blue, and yellow organic light emitting diodes

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