Role of optical properties of metallic mirrors in microcavity structures

Becker, Heinrich; Burns, S. E.; Tessler, Nir; Friend, Richard H.

doi:10.1063/1.363940

Cited by 89 publications

(51 citation statements)

References 10 publications

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“…The light was incident from HTL. The thickness of the semitransparent bottom metal mirror was determined from the condition for the reflectivity of the mirror to achieve optimal extraction of light from a microcavity R1 = min(R1t Rpc,lt , R055 ) (9) where R1t=l_-!-, (10) where m is the mode number, and n is the refractive index of the material inside the cavity, R1b055 is determined by the losses in the cavity (for large losses, approximately equal to the reflectivity of the top mirror R2), and…”

Section: Description Of the Modelmentioning

confidence: 99%

Angular dependence of the emission wavelength in microcavity organic light-emitting diodes

Djurišić¹,

Rakić

Majewski

2003

SPIE Proceedings

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In this work, we have calculated the emission wavelength dependence on the viewing angle for different combinations of metallic mirrors. The dispersion of the optical functions of ten different metals is fully taken into account using Lorentz oscillator model. The metals have been assigned to a function oftop (cathode) or bottom (anode) mirror based on their work function. Refractive index dispersion of organic layers, N,N'-disphenyl-N,N'-bis(3-methylphenyl)-l,1'-disphenyl-4,4'-diamine (TPD) and tris (8-hydroxyquinoline) aluminum (emitting layer) is taken into account via Cauchy model. The change of the emission wavelength with angle has been calculated iteratively to fully take into account wavelength dependence of indices of refraction and phase change. Calculations have been performed for different hole transport materials and different thickness of the emitting layer.

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Section: Description Of the Modelmentioning

confidence: 99%

Angular dependence of the emission wavelength in microcavity organic light-emitting diodes

Djurišić¹,

Rakić

Majewski

2003

SPIE Proceedings

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“…10 However, the deposition of indium tin oxide can be problematic due to sputter-induced damage to the organic material underneath, 11 whereas metal films absorb a significant amount of light and introduce additional micro-cavity effects. [12][13][14] Hence, the device development of highly efficient color-tunable OLEDs remains experimentally challenging: the color-tunable OLEDs that have been reported thus far demonstrate relatively modest efficiencies (,10% external quantum efficiency (EQE), ,10 lm W 21 ), despite the use of phosphorescent emitter systems. 15,16 Although these reports on vertical stacking of two independently controllable emission units have demonstrated only moderate performance, we believe that an efficient realization of such a system is a necessary and important step toward RGB full-color devices in which three independent emission units are stacked on top of each other.…”

Section: Introductionmentioning

confidence: 99%

Get it white: color-tunable AC/DC OLEDs

et al. 2015

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Organic light-emitting diodes (OLEDs) have gained considerable attention because of their use of inherently flexible materials and their compatibility with facile roll-to-roll and printing processes. In addition to high efficiency, flexibility and transparency, reliable color tunability of solid state light sources is a desirable feature in the lighting and display industry. Here, we demonstrate a device concept for highly efficient organic light-emitting devices whose emission color can be easily adjusted from deep-blue through cold-white and warm-white to saturated yellow. Our approach exploits the different polarities of the positive and negative half-cycles of an alternating current (AC) driving signal to independently address a fluorescent blue emission unit and a phosphorescent yellow emission unit which are vertically stacked on top of each other. The electrode design is optimized for simple fabrication and driving and allows for two-terminal operation by a single source. The presented concept for color-tunable OLEDs is compatible with application requirements and versatile in terms of emitter combinations. INTRODUCTIONIn recent years, organic light-emitting diodes (OLEDs) have evolved into a mature technology and OLEDs are now used in various display applications. OLEDs provide an internal charge-to-photon conversion efficiency of nearly 100% and deliver homogeneous emission over large areas, making them promising candidates for new and innovative lighting applications. 1 White OLEDs, in particular, offer great potential for energy-efficient general illumination: luminous efficacies of more than 90 lm W 21 , comparable to the best fluorescent tubes, have already been reported. 2,3 Furthermore, OLED-based light sources can be made mechanically flexible and transparent, offering new opportunities for architecture, visual art and decoration. 4 The reliable realtime tunability of the OLED emission color would impart further momentum to OLED technology on its way to becoming a widespread source of general illumination. Thus far, two different color-tuning concepts have prevailed in the literature. One exploits voltagedependent changes in emission color and was demonstrated as early as 1994 for OLEDs fabricated from polymer blends. 5 Voltage-dependent color shifts are the result of a variety of mechanisms, e.g., voltagedependent charge trapping, a spatial shift of the recombination zone, a modified exciton distribution, or exciton quenching at high current densities. [5][6][7] However, this approach has several drawbacks: not only are the mechanisms that lead to voltage-dependent color-shifts difficult to control, but adjusting the driving voltage also unavoidably results in a dramatic and undesired change in device brightness. The second concept overcomes the disadvantages of the voltage-controlled approach by using a stacked tandem OLED structure with two (or more) independently addressable units emitting light of different colors. 8,9 In comparison with the first method, this approach provides

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“…또 하나의 접근 방법은 OLED가 가지는 미소공진(microcavity) 구조를 이용하는 것이다 [32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51] . 배면발광형 OLED는 기본적 으로 음극인 금속과 양극인 투명전극 사이에 약한 미소공진 구조가 형성되는데, 이 때 금속이나 유전체 다층박막 등으로 공진구조를 강화시키면 OLED 발광색의 순도가 강화되어 색 재현성이 증가하거나 발광효율의 상승을 기대할 수 있다.…”

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Effects of a Dielectric Multilayer Mirror on the Lighting Efficiency of Organic Light-Emitting Diodes Studied by Optical Simulation

Lee¹,

Ko²

2015

Korean Journal of Optics and Photonics

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The effects of a dielectric multilayer mirror on the efficiency of organic light-emitting diodes (OLEDs) were investigated by using optical simulation. Adoption of a dielectric mirror consisting of alternating SiN and SiO2 layers narrowed the emission spectrum due to the microcavity effect, and increased the outcoupling efficiency by a few percent. The layer thicknesses of the dielectric mirror were adjusted to change the wavelength of the resonance mode, which may be used to increase the color purity.

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Role of optical properties of metallic mirrors in microcavity structures

Cited by 89 publications

References 10 publications

Angular dependence of the emission wavelength in microcavity organic light-emitting diodes

Angular dependence of the emission wavelength in microcavity organic light-emitting diodes

Get it white: color-tunable AC/DC OLEDs

Effects of a Dielectric Multilayer Mirror on the Lighting Efficiency of Organic Light-Emitting Diodes Studied by Optical Simulation

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