Thin-film transistor (TFT)-driven full-color organic light-emitting diodes (OLEDs) with vertically stacked structures are developed herein using photolithography processes, which allow for ...high-resolution displays of over 2,000 pixels per inch. Vertical stacking of OLEDs by the photolithography process is technically challenging, as OLEDs are vulnerable to moisture, oxygen, solutions for photolithography processes, and temperatures over 100 °C. In this study, we develop a low-temperature processed Al
O
/SiN
bilayered protection layer, which stably protects the OLEDs from photolithography process solutions, as well as from moisture and oxygen. As a result, transparent intermediate electrodes are patterned on top of the OLED elements without degrading the OLED, thereby enabling to fabricate the vertically stacked OLED. The aperture ratio of the full-color-driven OLED pixel is approximately twice as large as conventional sub-pixel structures, due to geometric advantage, despite the TFT integration. To the best of our knowledge, we first demonstrate the TFT-driven vertically stacked full-color OLED.
Metal oxides are intensively used for multilayered optoelectronic devices such as organic light-emitting diodes (OLEDs). Many approaches have been explored to improve device performance by ...engineering electrical properties. However, conventional methods cannot enable both energy level manipulation and conductivity enhancement for achieving optimum energy band configurations. Here, we introduce a metal oxide charge transfer complex (NiO:MoO
-complex), which is composed of few-nm-size MoO
domains embedded in NiO matrices, as a highly tunable carrier injection material. Charge transfer at the finely dispersed interfaces of NiO and MoO
throughout the entire film enables effective energy level modulation over a wide work function range of 4.47 - 6.34 eV along with enhanced electrical conductivity. The high performance of NiO:MoO
-complex is confirmed by achieving 189% improved current efficiency compared to that of MoO
-based green OLEDs and also an external quantum efficiency of 17% when applied to blue OLEDs, which is superior to 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile-based conventional devices.
The optical properties of the materials composing organic light‐emitting diodes (OLEDs) are considered when designing the optical structure of OLEDs. Optical design is related to the optical ...properties, such as the efficiency, emission spectra, and color coordinates of OLED devices because of the microcavity effect in top‐emitting OLEDs. In this study, the properties of top‐emitting blue OLEDs were optimized by adjusting the thicknesses of the thin metal layer and capping layer (CPL). Deep blue emission was achieved in an OLED structure with a second cavity length, even when the transmittance of the thin metal layer was high. The thin metal film thickness ranges applicable to OLEDs with a second microcavity structure are wide. Instead, the thickness of the thin metal layer determines the optimized thickness of the CPL for high efficiency. A thinner metal layer means that higher efficiency can be obtained in OLED devices with a second microcavity structure. In addition, OLEDs with a thinner metal layer showed less color change as a function of the viewing angle.
ZnSe/ZnS core/shell quantum dots (QDs) with efficient blue emission are in situ synthesized using a novel microfluidic reaction system. This advances research on both simple one‐step synthesis of ...core/shell QDs and their production using thermoplastic‐based microfluidic reaction systems. Furthermore, QD light‐emitting diodes (LEDs) are demonstrated using ZnSe/ZnS QDs as wavelength converters.
The incorporation of InP quantum‐dot/N‐doped multiwalled carbon nanotube (QD:NCNT) nanohybrids in the active layer of poly(3‐hexylthiophene)/indene−C60 bisadduct (P3HT/ICBA) bulk‐heterojuction solar ...cells enhances VOC and JSC. The QDs encourage exciton dissociation by promoting electron transfer, while the NCNTs enhance the transport of the separated electrons and eventual charge collection. Such a synergistic effect successfully improves the power conversion efficiency (PCE) from 4.68% (reference cells) to 6.11%.
Microdisplays based on organic light‐emitting diodes (OLEDs) have a small form factor, and this can be a great advantage when applied to augmented reality and virtual reality devices. In addition, a ...high‐resolution microdisplay of 3000 ppi or more can be achieved when applying a white OLED structure and a color filter. However, low luminance is the weakness of an OLED‐based microdisplay as compared with other microdisplay technologies. By applying a tandem structure consisting of two separate emission layers, the efficiency of the OLED device is increased, and higher luminance can be achieved. The efficiency and white spectrum of the OLED device are affected by the position of the emitting layer in the tandem structure and calculated via optical simulation. Each white OLED device with optimized efficiency is fabricated according to the position of the emitting layer, and red, green, and blue spectrum and efficiency are confirmed after passing through color filters. The optimized white OLED device with color filters reaches 97.8% of the National Television Standards Committee standard.
A single‐chamber system capable of depositing both organic and inorganic layers by initiated chemical vapor deposition (iCVD) and atomic layer deposition (ALD) is demonstrated to facilitate the ...fabrication of organic/inorganic hybrid thin film encapsulation (TFE). The chamber geometry and the process conditions of iCVD and ALD are similar to each other, which enabled the design of the single‐chamber system. Both organic and inorganic films deposited via the single‐chamber system produces films with their properties equivalent to those deposited in separate iCVD and ALD reactors. Alternating the deposition mode between iCVD and ALD produces organic/inorganic multilayers with outstanding barrier properties as well as optical transparency mechanical flexibility.
A single‐chamber system that can conduct both initiated chemical vapor deposition (iCVD) and atomic layer deposition (ALD) is demonstrated in this study. From the single‐chamber system, thin film encapsulation (TFE) composed of alternating organic and inorganic layers is fabricated. The TFE exhibited outstanding properties suitable for encapsulation of organic light‐emitting diodes.
We demonstrate independently and simultaneously controlled color-tunable organic light-emitting diodes (OLEDs) with vertically stacked blue, green, and red elements. The blue, green, and red elements ...were placed at the bottom, middle, and top positions, respectively, forming color-tunable OLEDs. The independently driven blue, green, and red elements in the color-tunable OLEDs exhibited low driving voltages of 5.3 V, 3.0 V, and 4.6 V, as well as high external quantum efficiencies of 11.1%, 10.9%, and 9.6%, respectively, at approximately 1000 cd/m
. Each element in the color-tunable OLEDs showed high-purity blue, green, and red colors with little parasitic emission owing to the delicately designed device structure resultant from optical simulations. The color-tunable OLEDs could produce any colors inside the triangle formed with blue (0.136, 0.261), green (0.246, 0.697), and red (0.614, 0.386) Commission Internationale de l'éclairage (CIE) 1931 color coordinates. In addition, the correlated color temperatures (CCTs) of white colors in the color-tunable OLED can be easily changed from the warm white to the cool white by controlling the red, green, and blue emissions simultaneously. The white colors in the color-tunable OLED have the CIE 1931 color coordinate of (0.304, 0.351), with a CCT of 6289 K and (0.504, 0.440), with a CCT of 2407K at the driving voltage of 5 V (blue), 2.8 V (green), 4.4 V (red), and 4.6 V (blue), 3 V (green), 5 V (red), respectively. Furthermore, the white color in the color-tunable OLED exhibited a high color rendering index (~88.7) due to vertically stacked three color system. Moreover, we successfully fabricated a large-sized, 14 × 12 pixel array of the color-tunable OLEDs to demonstrate lighting and display applications, respectively.
Even though it is in high demand to introduce a nano-structure (NS) light extraction technology on a silicon nitride to be used as a thin film encapsulation material for an organic light-emitting ...diode (OLED), only an industry-incompatible wet method has been reported. This work demonstrates a double-layer NS fabrication on the silicon nitride using a two-step organic vapor phase deposition (OVPD) of an industry-compatible dry process. The NS showed a wrinkle-like shape caused by coalescence of the nano-lenses. The NS integrated top-emitting OLED revealed 40 percent enhancement of current efficiency and improvement of the luminance distribution and color change according to viewing angle.
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Organic-inorganic hybrid perovskite nanocrystals (PNCs), have superior optical properties that meet the high color standard of Rec. 2020, but poor environmental instability, which ...impedes their practical applications as light emitters in displays. Here, we report exceptionally stable PNC-incorporated color-converting material that, and that maintains its luminescence in various harsh environments. Our main approach is to use two kinds of siloxane hybrid materials: a passivating ligand on the surface of PNCs (M-PNC) and an encapsulating matrix (MP-SH); they induce significantly improved stability against moisture, oxygen, and light. The MP-SH film (M-PNC encapsulated by siloxane hybrid) was stable for 100 d in water, air at 85 °C with 85% relative humidity, various polar solvents, and continuous blue light irradiation without any additional protecting layer. Furthermore, we investigate reversible optical property healing characteristics that are induced by water-induced defect passivation mechanism, suppressing non-radiative recombination in perovskite crystals. We demonstrate a color-converted organic light-emitting diode that uses MP-SH and that has excellent optical characteristics and operating reliability. This approach to increasing the environmental stability of PNCs provides great potential toward commercialization of PNCs for use in stable color-converting layers of displays.
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