A Full-Color Transparent Metal-Free Stacked Organic Light Emitting Device with Simplified Pixel Biasing

Parthasarathy, Gautam; Gu, G.; Forrest, Stephen R.

doi:10.1002/(sici)1521-4095(199908)11:11<907::aid-adma907>3.0.co;2-l

Cited by 57 publications

(21 citation statements)

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“…There are only few publications that describe vertical stacking of three emission units for a full-color OLED pixel. The most important work on this topic has been published almost two decades ago, however, when compared to current state-of-the-art display technology, the devices have only rather low brightness, poor electrical performance, low efficiency, and only mediocre color gamut 1 , 2 .…”

Section: Introductionmentioning

confidence: 99%

Three-terminal RGB full-color OLED pixels for ultrahigh density displays

Fröbel

Fries

Schwab

et al. 2018

Sci Rep

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In recent years, the organic light-emitting diode (OLED) technology has been a rapidly evolving field of research, successfully making the transition to commercial applications such as mobile phones and other small portable devices. OLEDs provide efficient generation of light, excellent color quality, and allow for innovative display designs, e.g., curved shapes, mechanically flexible and/or transparent devices. Especially their self emissive nature is a highly desirable feature for display applications. In this work, we demonstrate an approach for full-color OLED pixels that are fabricated by vertical stacking of a red-, green-, and blue-emitting unit. Each unit can be addressed separately which allows for efficient generation of every color that is accessible by superpositioning the spectra of the individual emission units. Here, we use a combination of time division multiplexing and pulse width modulation to achieve efficient color mixing. The presented device design requires only three independently addressable electrodes, simplifying both fabrication and electrical driving. The device is built in a top-emission geometry, which is highly desirable for display fabrication as the pixel can be directly deposited onto back-plane electronics. Despite the top-emission design and the application of three silver layers within the device, there is only a minor color shift even for large viewing angles. The color space spanned by the three emission sub-units exceeds the sRGB space, providing more saturated green/yellow/red colors. Furthermore, the electrical performance of each individual unit is on par with standard single emission unit OLEDs, showing very low leakage currents and achieving brightness levels above 1000 cd/m2 at moderate voltages of around 3–4 V.

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Section: Introductionmentioning

confidence: 99%

Three-terminal RGB full-color OLED pixels for ultrahigh density displays

Fröbel

Fries

Schwab

et al. 2018

Sci Rep

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“…S 1 in the Supplementary Information). Two subunits are stacked vertically 18 , 19 in a configuration that allows for emission through the substrate, i.e., a bottom emitting layout. Compared to conventional OLEDs, this device shows an increased overall thickness of ~800 nm, which is needed to realize the desired optical effects.…”

Section: Resultsmentioning

confidence: 99%

Real-time beam shaping without additional optical elements

et al. 2018

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Providing artificial light and enhancing the quality of the respective light sources is of continued interest in the fields of solid state, condensed matter, and semiconductor physics. Much research has been carried out to increase the luminous efficiency, lifetime and colour stability of such devices. However, the emission characteristics of a given light source do not necessarily comply with today’s often sophisticated applications. Here, beam shaping addresses the transformation of a given light distribution into a customized form. This is typically achieved by secondary optical elements often sporting elaborate designs, where the actual light source takes up only a small fraction of the system’s volume. Such designs limit the final light source to a single permanent operation mode, which can only be overcome by employing mechanically adjustable optical elements. Here we show that organic light-emitting diodes (OLEDs) can enable real-time regulation of a beam shape without relying on secondary optical elements and without using any mechanical adjustment. For a red light-emitting two-unit OLED architecture, we demonstrate the ability to continuously tune between strongly forward and strongly sideward emission, where the device efficiency is maintained at an application-relevant level ranging between 6 and 8% of external quantum efficiency for any chosen setting. In combination with additional optical elements, customizable and tuneable systems are possible, whereby the tuning stems from the light source itself rather than from the use of secondary optics.

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“…Unlike a traditional tandem light‐emitting device, these highly transparent OLEDs provide the possibility of stacking two complete emitting cells together, enabling the luminance of different emitting cells in the same pixel, which has been predicted for stacked OLEDs (SOLEDs). [ 43–46 ] SOLEDs will not only increase the pixel density in displays but also present a stereo image due to the vertical distance between each emitter, as shown in Figure 1b. However, due to the limited transparency and potential energy barrier induced by a traditional cathode structure, previous independent cells for SOLEDs have shown poor efficiency and transparency.…”

Section: Figurementioning

confidence: 99%

Highly Conductive Alkaline‐Earth Metal Electrodes: The Possibility of Maintaining Both Low Work Function and Surface Stability for Organic Electronics

Liu

Ding

Chen

et al. 2020

Advanced Optical Materials

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The realization of a highly efficient and transparent light‐emitting display isan ambitious but highly desirable goal since several obstacles need to be solved. One of the most challenging issues is the fabrication of a suitable transparent cathode on the top emitting surface. Evaporated Ca thin film is one theoretically promising candidate due to its remarkable optical transparency, conductivity, and matched work function (WF) on the electron injection side. However, until now, keeping metallic Ca working as a stand‐alone electrode is not possible because its highly reactive characteristics cause ultrathin Ca film to react with organics. In this work, atomic layer deposition ZnO is presented with the intention of protecting a vulnerable ultrathin Ca layer while preserving its low WF in the entire structure. In this research, a transparent cathode that maintains a low WF of 3.31 eV is built, enabling highly transparent (nearly 90% in the visible range) organic light‐emitting diodes with external quantum efficiencies that reach 22.7%, 19.3%, and 17.9% for green, yellow, and blue emissions, respectively, and reaching an emission balance. The luminance of the devices is about three times higher when compared with the devices without protective structures, which are even likely to fail to operate.

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A Full-Color Transparent Metal-Free Stacked Organic Light Emitting Device with Simplified Pixel Biasing

Cited by 57 publications

References 0 publications

Three-terminal RGB full-color OLED pixels for ultrahigh density displays

Three-terminal RGB full-color OLED pixels for ultrahigh density displays

Real-time beam shaping without additional optical elements

Highly Conductive Alkaline‐Earth Metal Electrodes: The Possibility of Maintaining Both Low Work Function and Surface Stability for Organic Electronics

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