Technical / Research - Page 2

Researchers from National Taiwan University, together with colleagues from Yuan Ze University, National Dong Hwa University and Academia Sinica, have developed a very high efficiency blue TADF OLED device, by adopting a favorable horizontal oriented host material.

The researcher designed a new host material (4Ac26CzBz) that is made from acridan and carbazole moieties linked to a benzimidazole core. The host material exhibits a wide optical gap (Eg) and high triplet energy (T1) of 3.3 and 3.0 eV, respectively. The researchers used 4TCzBN as the blue-light TADF dopant, and report a remarkably high device external quantum efficiency of 35.8 % (59.8 cd/A and 62.8 lm/W) and a low turn-on voltage (<3 eV). The device features with significant suppression of the efficiency roll-off, maintaining a high efficiency of 29.7 % as luminance at 1000 cd/m².

Researchers from Korea's KAIST, in collaboration with Dong-a University and ETRI have developed a new stretchable OLED structure that is made from 3D rigid islands, or bumps. These so-called 3D-Pop islands remain unchanged as the display itself stretches and so maintain excellent performance.

The OLED islands are connected with parts that are curved in shape (similar to a horseshoe) that can be deformed while still operating normally, even at 500% tension. The whole structure can simultaneously utilize hinge-type rotation and tension of the bending connection connector, and is so not limited to a 2D plane. Even at 40% elasticity, the light emitting area remains at 85%. 

Researchers from ETH Zürich and the Huazhong University of Science and Technology developed a new scalable fabrication technology that enables the deposition of extremely small OLED pixels. The so-called nano-OLEDs achieve a pixel density of 84,000 PPI, or even higher. The pixel size is around 100 nm, the smallest pixels ever reported.

The method is based on direct nanomolecular patterning of the OLED materials, realized by self-aligned evaporation through nanoapertures fabricated on a free-standing silicon nitride film adhering to the substrate. The researchers report that the average nano-OLED EQEs is up to 10%. 

Researchers from Tsinghua University in Shenzhen, China, have managed to dramatically increase the stability of OLED devices by the adoption of deuterated host material.

The researchers, led by Prof. Man-Chung Tang, have designed and synthesized deuterated anthracene-based hydrocarbon PNA as the new host material. The researchers have observed that the faraday loss decreases with the increase of the deuteration degree.

During iMID 2024, Samsung Display's eVP Yi Chung said that the company plans to reduce the power consumption of its OLED panels by over 50%. SDC is developing several technologies, each contributing to the same efficiency goal.

SDC did not detail its plans exactly, but it did mention some of the new technologies it is working on - polarizer-free OLEDs (these have been commercialized already), multi-frequency driving (demonstrated by other OLED makers), tandem OLED architecture and the adoption of high efficiency blue PHOLED emitters.

A report from Korea says that LG Display has successfully developed an OLED panel that is based on a blue phosphorescence emitter. The blue PHOLED, provided by Universal Display, offers 100% IQE, up from 25% used by current fluorescence emitters. This will result in around 20-30% power saving for the display itself (depending on the images shown).

UDC has been developing blue emitters for many years, and recently the company said that the development will take a few more months and won't be ready in 2024. The main challenge is increasing the lifetime of the materials. However LG Display has adopted a tandem design to enable a commercially ready display, perhaps even sooner than UDC planned.

Samsung Display's Lee Chang-hee, VP and head of SDC's research center, gave a talk during K-Display 2024, and updated that Samsung is progressing towards a next-generation blue OLED emitter technology in two tracks.

SDC is working with Universal Display, to adopt the company's blue PHOLED system. This is progressing, but SDC says that the pace is slow - indeed we heard from UDC lately that the introduction of a commercial material will take longer than expected.

Researchers from China's Northeast Normal University developed a new integration strategy (called “discrete preparation-multilayer lamination”) that enables the deposition of OLED devices directly on top of OTFT transistors, to enable high-aperture wearable skin-patch OLED devices.

The new method starts with the preparation of the different layers on different substrates to avoid chemical and physical damage caused by process interferences, and then the transfer of the OLED devices onto the OTFT transistors. The researchers say that the resulting AMOLED display offers a high apreture ratio (83%), high mobility

A few months ago researchers from the Fraunhofer IPMS announced that they have developed semi-transparent yellow high resolution OLED microdisplays, that are significantly lighter than conventional combiner-based optical see-through near-to-eye systems. 

The Fraunhofer IPMS now announced that it has managed to increase the transparency of these microdisplays to 45%. 

Researchers from Soochow University and the University of Muenster have developed a method to produce ultra high resolution OLED microdisplays - with up to 20,000 PPI.

To achieve such high resolution, the researchers used a method they refer to as "first surface patterning and then patterned growth". The idea is that the substrate is first patterned using lithography, and then the organic materials are deposited. Following the substrate treatment, the organic materials are diffusing on the substrate, selectively grown on the designated areas.