Technical / Research - Page 6

Researchers from the Tokyo Institute of Technology, Osaka University, University of Toyama and Shizuoka University have developed a fluorescent blue (462 nm) OLED device that features an ulta-low turn-on voltage of 1.47 V (at 100 nits). The researchers say this is very low, as similar commercial blue devices typically need around 4 V.

To achieve that low turn-on voltage, the researchers built a new device, as they realize that the choice of materials significantly influences the device's turn-on voltage. The device itself is an upconversion OLED.

Researchers from the Korean Advanced Institute of Science and Technology (KAIST) and the Asan Medical Center (AMC) have developed the world's first OLED-based catheter for phototherapy within internal organs.

OLED-based light therapy has been researched, and even commercialized, before, but only for external use. This is the first time that such a device has been developed for internal use.  The device developed by the joint research team is a catheter-shaped OLED platform that can be directly inserted into tubular organs like the duodenum and is water-resistant. 

Researchers from the University of Manchester, led by Prof. Alexander Romanov, developed a promising new Carbene-Gold-Arylacetylide (CMAc) OLED near UV emitter type. The researchers also detail a strategy to develop longer device lifetimes for such emitters.

The new emitter exhibits an efficiency of 1% EQE, and a lifetime of 20 minutes at a practical brightness of 10 nits (LT50). This is low compared to commercial OLEDs - but it is actually quite outstanding for such an emitter, and the researchers say that this is among the longest lifetimes for a near UV-OLED at a practical brightness ever reported. In addition, organic fluorescent and TADF emitters rarely exceed 1% EQE at practical brightness.

Researchers from South China University of Technology and Guangzhou New Vision Opto-Electronic have found that the lifetime and current efficiency of a tandem OLED device can be greatly improved by adding an ultra-thin Ytterbium (Yb) metal layer through the charge generation layer (CGL).

The experiments detail an ultra-thin Yb metal layer with low work function, high transmittance, and large atomic radii, added to a light-green tandem OLED devices. The new device exhibited a lifetime of 308 hours (T90) at an initial brightness of 10,000 cd/m² - which is 362 times (!) longer than that of a similar device without the Yb layer (T90 = 0.85 hours). The lifetime of the same material in a single-layer configuration (not a tandem device) was 49 hours (T90).

Researchers from Japan's Keio University, in collaboration with Mitsubishi Chemical Corporation, developed a new method to accelerate the design of OLED materials, using a combination of classical computing with quantum computing.

The new approach combines a 'classic' machine learning model with a quantum-classical computational molecular design. Demonstrating the new approach, the researchers discovered a highly efficient OLED emitter, a deuterated derivative of Alq₃. The new emitter is not only highly efficient, it is also easy to synthesize. 

Researchers from Korea's KAIST institute, in collaboration with Gyeongsang National University developed a new TADF OLED deep-blue emitter molecule that achieves an EQE of 33%. Combined with a fluorescent emitter to create a hyperfluorescence system, the researchers achieved an EQE of 35.4%, with mitigated efficiency roll-off. The researchers say that this is the world's highest-efficiency narrow-band deep-blue TADF OLED emitter.

To develop the new emitter the researchers introduced sterically hindered peripheral phenyl groups to boron-based TADF emitter. The resulting material, o-Tol-ν-DABNA-Me, offers a pure narrowband emission that is far less sensitive to concentration compared to standard TADF emitters.

Researchers from Germany's Karlsruhe Institute of Technology (KIT) and Shanghai University developed a new high-efficiency exciplex deep-blue OLED emitter material. The researchers say that this new materials achieves a external quantum efficiency (EQE) of 20.35% - a new world record for deep-blue emission.

The researchers explain that their exciplex strategy is based around a new molecule type with carbazole and triazine fragments linked by a silicon atom. The molecules assemble into nanoparticles which emit light in a different mechanism compared to standard single-molecule emitters. The energy levels of the electron-donating carbazole fragments and electron-accepting triazine fragments can be adjusted independently of each other to enable highly efficiency and stable red, green and blue OLED emitters.

The following is a sponsored post by Cambridge Isotope Laboratories

OLED has become the display technology of choice for many commercial products such as smartphones, laptops, tablets, TVs, automotive dashboards and wearables. OLED has advantages with improved image quality (better contrast, higher brightness, fuller viewing angle, wider color range, and faster refresh rates), lower power consumption, and simpler designs (ultra-thin, flexible, foldable, and transparent displays).

Cambridge Isotope Laboratories plant in Xenia, OH, USA

OLED, however, faces several technical challenges. While OLED TVs yield better picture quality than common LCDs, they are usually less bright. Research using a compound that has at least one hydrogen replaced with its heavier isotope, deuterium, is showing promise toward achieving greater brightness. Since the bonds between carbon and deuterium are stronger than those between carbon and hydrogen, materials made with deuterated compounds tend to have a longer lifetime, which allows OLED displays to run brighter but still last as long.

A few months ago we reported on research conducted at Germany's Max Planck Institute, led by Prof. Paul W.M. Blom, that looks into single-layer OLED devices. In such devices, a single TADF OLED emitter layer is sandwiched between two electrode - a much simpler design compared to commercial OLED devices that use multilayer stacks, sometimes with 10 or more layers.

The researchers the the MPI say that in fact it is possible to develop highly efficient OLEDs with just the TADF emitter, as there's no fundamental reason or major benefits that arise from multilayer OLEDs. The researchers continue their work, and now they have developed a new single-layer blue OLED in which every injected electron is converted into a photon - or 100% IQE. This is the first time that such a single-layer OLED device was demonstrated (see image above).

The following is a sponsored post by Excyton

UK-based Excyton is happy to announce that it will showcase its novel TurboLED OLED architecture and technology at the 2023 Displayweek event (May 23-25, Los Angeles, California). Excyton has been accepted to participate at the 2023 I-Zone event.

TurboLED is a game-changing technology that offers a dramatic boost to the performance of displays. In a TurboLED OLED display, each pixel comprises deeper and lighter color red, green and blue emitters to maximize performance - in fact Excyton has shown that the TurboLED architecture leads to a 50% reduction in power consumption, a 3X improvement in emitter lifetime and an increased color gamut. TurboLED displays are especially suited for demanding applications, such as IT displays, automotive displays, gaming monitors, AR/VR headsets, smartphones and wearables.