Technical / Research - Page 23

Researchers from the Fraunhofer FEP announced a new development that can reduce the power consumption of OLED microdisplays. The power reduction is enabled by new chip and control electronics, that now only handles pixel changes and does not refresh the entire display all at once.

The researchers say that this development enabled a drastic reduction in power consumption - which is somewhat surprising. The new microdisplays (which are monochrome - green) use 1 to 4 mW, which they say is a fraction of the power consumed by the Fraunhofer's previous generation display - a color (WOLED+CF) bi-directional OLED (so this is not a fair comparison of course).

The US DoE published a new CALiPER report made by the PNNL laboratory, with photometric testing, laboratory teardowns and accelerated lifetime testing of OLED luminaires. As you can see in the photo below, the four luminaries (from top-left, clockwise) are the OTI Aerelight, Acuity Brands Chalina and Acuity Brands Nomi (single panel and dual panel).

The report contains a lot of interesting information (see the link below to access the PDF). The PNNL researchers find that efficiency of OLED luminairies is still low compared to LED lamps - ranging from 23 lm/W to 45 lm/W. The OLED panels themselves are more efficient (42 - 55 lm/W) but the reduction in efficiency is mostly due to very inefficient transformer and driver selections and combinations.

Switzerland-based R&D tools provider Fluxim released a new simulation tool called Laoss. Laoss is aimed specifically for large area organic electronic devices - such as large OLED display and lighting panels and perovskite solar cells.

The Laoss software is used to design optimal electrode lay-outs of any shape with and without current carrying grids. Fluxim says that a carefully designed electrode layout avoids non-uniformities that arise due to the resistance of the electrode and charge injecting layers. Laoss tool can be used in combination with Fluxim’s Setfos software to design the layer stack of the OLED/PV device as well as with results from the Paios measurement platform.

Korea equipment maker DAWONSIS developed a new OLED deposition process that is based on FMM but according to the company can be scalable to large-area deposition. This could theoretically enable efficient evaporation-based OLED TV production.

The so-called Joule Heating Deposition process use a large area material source (as opposed to point-sources or line-sources currently used) using a conductive film that is efficiency heated using voltage induction. According to DAWONSIS this process is scalable and also efficient in terms of material usage (which is about 70%-80%).

Exactly one year ago at IFA 2016, Panasonic unveiled its first OLED TV, the 65" curved 4K TX-65CZ950. Now Panasonic unveiled a new "reference" OLED TV prototype, with an aim to show what is possible with next-gen OLED technology.

Panasonic said that it achieved significant progress with near-black reproduction, by applying its plasma self-illuminating experience. It's not clear what is meant exactly, but this probably related to software algorithms Panasonic is developing to increase the quality of the OLED TV image. The panel, of course, is supplied by LG Display.

The Fraunhofer Institute is working on alternative light sources for photo therapy, and Flexible OLED technology is prime candidate because it is light weight, can be flexed and does not produce almost any heat (unlike LED-based lighting).

Before flexible OLEDs are actually used in such treatment, though, it is important to know if OLEDs carry any potential toxic risks. The Fraunhofer FEP performed an initial study on in vitro cell cultures afflicted by defined damage. The researchers used flexible 10x10 cm green OLEDs, and found that the OLEDs positively stimulated the damaged cells, as expected. The tests showed now cytotoxity in the material systems, including when the OLEDs were bent (this increases the chance of material leakage from the OLEDs).

Researchers from Japan's Semiconductor Energy Laboratory (SEL) developed a new OLED device architecture that enables efficient, long-lasting and low-drive voltage OLEDs, at practical brightness levels.

The researchers call the new device architecture exciplex-triplet energy transfer, or ExTET. The image above shows the elementary process and its energy state diagram. To create the emissive layer of the ExTET, the researcher took a film with an electron-transporting material (ETM) and a hole-transporting material (HTM) and doped it with a phosphorescent dopant. Direct recombination between the electrons at the LUMO level and the hole at the HUMO level forms a charge-transfer excited complex (exciplex) - and the phosphorescent emission occurs via energy transfer from the exciplex to the dopant.

Reports from China suggest that LG Display is considering changing the basic structure of its white OLED panels (WOLED) used in LGD's OLED TVs. LGD is currently using yellow and blue OLED materials to create a white OLED, but now LGD may switch to an RGB based mix.

It's not clear from the Chinese reports (which are unverified yet, of course) - but it's likely that LGD will not switch to a direct-emission RGB structure, but rather use the RGB materials to create a white OLED and remain with a color-filter based design. Switching from Y/W to R/G/B may enable LGD to achieve higher color purity - and so a larger color gamut, and may also be more efficient.

Last week we reported about a new large-scale computer-driven material screening process that was developed by Researchers from Harvard University, MIT and Samsung.

The so-called Molecular Space Shuttle system combines theoretical and experimental chemistry, machine learning and cheminformatics, with an aim to quickly identify new OLED molecules (the system was already used to deisgn more than a 1,000 new high-performance blue-light emitting molecules). Today Kyulux announced that it secured a license to Harvard University’s Molecular Space Shuttle deep learning system.

Researchers from Harvard University, MIT and Samsung developed a large-scale computer-driven material screening process that incorporates theoretical and experimental chemistry, machine learning and cheminformatics, with an aim to quickly identify new OLED molecules.

The so-called Molecular Space Shuttle system was used to design more than 1,000 new high-performance blue-light emitting molecules. It seems that there is still a lot of work ahead to find the best new candidates and actually test these molecules, but this may be a promising new direction in OLED molecule research.