Technical / Research - Page 13

Researchers from Dresden's Technical University (TUD) developed a new OLED device structure that combine vertical organic permeable base transistors (OPBT) and OLEDs materials - organic permeable base light-emitting transistor, or OPB-LET.

The new design successfully combines the function of a highly efficient switching transistor and an organic light-emitting diode. The OLED transistors (OLETs) are three-terminal devices combining a thin-film transistor with a light-emitting diode. Unlike previous OLETs, the OPB-LET offer high performance, thanks to the permeable base electrode located at the center of the device. The electrode forms a distinctive optical microcavity and so regulates the charge carrier injection and transport.

Researchers from the UK's UCL and Italy's IIT developed OLED-based smart temporary tatoos. Similar to children's "sticker" type tatoos, these small devices can be transferred to the skin by being pressed and washed with water.

Such devices could in the future be used to short-term sensors (for example to detect when an athlete is dehydrated during an event) or in fruit packaging to signal when a product has passed its expiry date.

Researchers from the Helmholtz Center Berlin for Materials and Energy and the Physics Department of the Humboldt University Berlin, together with Oreltech, developed a new flexible OLED prototype that uses Oreltech's silver-inks to deposit electrodes on PET substrates.

The researchers report that the new device outperforms ITO-based devices in both efficiency and luminance - and they are offer better bending stability.

Researchers from Soochow University, in collaboration with a wide team of scientists from China and Japan (including Prof. Adachi from Kyushu University) developed a TADF emitter material compound that features high efficiency and a narrow color spectrum.

Up until now, most TADF emitters featured a wide spectrum, which limits the adoption of TADF materials in displays as they cannot enable a wide color spectrum. To overcome this problem companies employ a structure in which the TADF emitter is combined with a narrow-spectrum fluorescence emitter (so-called Hyperfluorescence).

Scientists from North Carolina State University and the University of Texas have developed and demonstrated a new approach for designing photonic devices. The new method enabled the team to control the direction and polarization of light from thin-film LEDs, overcoming the widely known obstacles of beam shaping that arise from their Lambertian nature. Such LEDs with directional and polarized light emission could be useful for many photonic applications.

The researchers demonstrated that this approach could be used to emit directional and polarized light from an OLED devices without external optical elements.

Researchers from Osaka University developed the best performing heavy-metal-free room-temperature phosphorescence (RTP) OLED emitters.

The researchers say that the new emitter (called SiAz), made entirely out of carbon, hydrogen, nitrogen, and silicon atoms, combines the mechanisms of TADF and RTP to create an efficient emitter system.

Researchers from Kyushu University reported that they have developed a promising new blue OLED emitter system, based on a two-unit stacked tandem hyperfluorescence OLED with improved singlet-excited-state energy transfer from a sky-blue assistant hetero-donor-type TADF (HDT-1) dopant.

The research reports that the new emitter system offers a pure-blue color (CIE 0.13, 0.16), a narrow spectrum (full-width at half-maximum of 19 nm), an EQE of 32% at 1,000 cd/m² and a lifetime of 18 hours LT95. The lifetime is still lacking, but with stricter control of device fabrication and procedures the researchers say they expect that device lifetimes will further improve to rival commercial fluorescent blue OLEDs.

Researchers from the Imperial College London have devised a method to create strong chiral light emitting polymers OLEDs. These OLED devices emit efficient polarized light - which means that they could be used to create OLEDs without an anti-reflection polarizer filter and thus enable higher efficiency displays.

The researchers discovered that using thin films of aligned polymer LED devices shaped like fusili pasta it is possible to emit high chirality light.

A couple of months ago we reported that researchers at UDC developed an OLED device with plasmonic decay rate enhancement that dramatically increase device stability. It turns out that UDC filed for two new trademark applications that seem to hint it is aiming to commercialize this technology.

The two trademarks at PLASMON PHOLED and PLASMONLED, which both of course indicate that these are emitters that adopt plasmon technology.

Researchers from Canada's Polytechnique Montréal and the Université de Montréal developed a new near-infrared (840 nm) TADF OLED device that is 300% more efficient than existing ones. The IQE of the new deice is 3.8% - which is the best all-organic OLED emitter ever developed above 800 nm.

Photograph of the Polytechnique Montréal crest taken using visible and infrared illumination. Credit: Pr Sébastien Kéna-Cohen

To create the new OLED device, the researchers developed two new organic compounds - and were inspired by a class of molecules previously used for biomedical imaging.