Technical / Research - Page 22

Researchers from South China University of Technology developed a new OLED structure that promises to enable low-cost efficient fluorescent OLED devices. The so-called pn-OLED structure is inspired by p-n junction theory and inorganic LED design.

The pn-OLED uses a highly-efficient emission-layer-free OLED, in which the p-type and n-type organic semiconductors are sandwiched vertically between an ITO anode and a lithium fluoride/aluminum cathode. The luminescent center of the pn-OLED is located in the pn junction region. The light-emission behavior of this device is a result of the synergetic energy release from both the p-type and n-type materials. This is in contrast to conventional OLEDs, where the light generation occurs from single-molecule emitters.

CSEM and Sefar developed low cost flexible, transparent, highly conductive electrodes made of fabric substrates comprising flexible metallic wires and polymeric fibers woven together in a highly transparent and flexible polymer. CSEM and Sefar produced an OLED lighting prototype that uses a backplane based on these new electrodes.

Sefar calls this new backplane a fabric SEFAR TCS Planar backplane. These backplanes are manufactured using low-cost, high-throughput processes under standard ambient clean room conditions. The OLED lighting device prototype was deposited using a coating technology and is made from polymer solution materials.

LG is demonstrating a new technology which they call Crystal Sound OLED - which is an OLED panel that contains an embedded sound system. LG says that this technology is only possible with an OLED panel as it does not require backlights.

LG Display demonstrated a 65" Crystal Sound OLED - and the company says that it provides a better immersive viewing experience as the sound comes directly from the characters on the screen and not from an off-center sound speaker. LGD says it will unveil 55" and 65" 4K Crystal Sound OLED TVs in the future.

The European GLADIATOR project, led by the Fraunhofer Institute, developed a functional flexible OLED lighting panel based on graphene electrodes. This new panel is 2 x 1 cm in size - much larger the previous prototype developed as part of that project last year.

The GLADIATOR project will conclude in April 2017. In the following months, the researchers aim to improve the graphene electrode by minimizing the impurities and defects that occur during the transfer of the graphene sheet. The project's leader, Beatrice Beyer, estimate that such OLEDs with graphene electrodes could be commercialization within 2-3 years. In September 2015 Graphene-Info posted an interview with Beatrice, discussing the technology behind this project.

Researchers from Kyushu University discovered that lifetime of OLED displays is compromised during the evaporation production process due to small amounts of impurities in the vacuum chamber.

The researchers examined the production process and found that there are many impurities floating in the vacuum even when the deposition chamber is at room temperature. They found a strong correlation between the time the OLED is placed in the deposition chamber and its lifetime.

Researchers at Tohoku University in Japan developed a super flexible organic liquid crystal device, which they say are promising for next-generation highly-flexible LCD displays. The new device is formed from ultra-thin plastic (polyimide) substrates that are firmly bonded by polymer wall spacers.

The transparent polyimide substrate (made by Mitsui Chemicals) are about 10 um thick each, and feature heat resistance and the ability to form fine pixel structures, including transparent electrodes and color filters. The refractive index anisotropy is extremely small, making wide viewing angles and high contrast ratio possible.

Reserachers from Korea's KAIST institute developed a process to deposit OLED displays on textile substrates. The substrate uses fabrics made from several-micrometer-thick fibers. Using a planarization process the researchers created a fabric as flat as a piece of glass.

The OLED was deposited on this flat fabric using regular evaporation equipment. Using thin-film encapsulation, a lifetime of 1,000 hours was achieved. The textile OLED is much more flexible than a plasic based one, and may find uses in wearables. Of course the performance needs to be increased and this just a research project at this stage.

Researchers from the Holst Centre developed a new process to deposit semiconductor layers with better performance and high throughput than PVD-based process. the new process is based on scalable, atmospheric-pressure process spatial-ALD.

The Holst Centre used sALD to deposit IGZO backplanes that achieved charge carrier mobilities of 30 to 45 cm²/Vs. The researchers say that similar backplanes deposited with PVD (supttering) achieve about 10 cm²/Vs. The sALD layers also exhibited low off current, switch-on voltages around 0 V and excellent bias stress stability.

Sunic System recently unveiled a new evaporation-FMM based AMOLED system that enables high resolution deposition - Sunic says it will enable PPI up to 2,250 PPI. Sunic's new technology makes use of a plane source for evaporating OLED materials, as opposed to the currently-used linear source. Such high resolution displays will be very useful for VR applications.

Sunic System now announced that it succeeded in implementing 1.1um shadow distance by using the new plane source evaporation and 100um shadow mask. Such a small shadow distance can achieve 1,000 to 1,500 PPI resolutions. The company's next step is to lower shadow distance to 0.37um - which will indeed enable 2,250 PPI and 11K high-resolution mobile AMOLEDs.

Researchers from South China University of Technology (SCUT) demonstrated a new MgO-based OLED encapsulation layer. The researchers say that MgO provides an efficient barrier at a low cost, and can be deposited in low temperatures.

The researchers say that this is the first time that MgO is used for OLED encapsulation, but this material has a number of advantages - a low refractive index, a wide bandgap, high dielectric constant, high chemical stability and the lack of UV irradiation treatment requirements.