Technical / Research - Page 18

Motorola has been granted an interesting patent that aims to solve screen deformation with foldable displays. Motorola says that one of the issues with foldable displays is that they deform in low temperatures.

Motorola suggests using a temperature sensor that detects when the display is deformed, and then the hinge is heated so that the display is automatically corrected. This could be used to create foldable OLEd phones that bend both inward and outwards, and can work with more than one hinge (so that you can fold a display several times).

Researchers from Penn State University have demonstrated 3D OLED lighting devices, inspired by the Japanese Kirigami art of paper cutting the folding.

The researchers started with flexible OLED lighting devices produced on thin plastics, which they then cut and folded to create lighting-emitting 3D structures.

Researchers from the Universitat Autònoma de Barcelona and TU-Dresden have demonstrated that ultra-stable film formation can be used to to improve the performance of OLED devices.

The researchers grew (using evaporation) the organic materials as ultrastable glasses - a growth condition that allows for thermodynamically most stable amorphous solids. Testing four different phosphorescent emitters, the researchers show significant (over 15%) increases of efficiency and operational stability. The researchers also say that these growing conditions are expected to even be more useful for TADF materials.

Researchers from the University of Michigan developed a new method to cost-effectively extra more light out of OLED displays. To achieve that, the researchers used a Sub-Electrode Micro-Lens Array (SEMLA) placed between the bottom transparent ITO electrode and the glass substrate. Testing on green and white PHOLEDs, the researchers say the SEMLA enhanced light output by a factor of 2.8 (green) and 3.1 (white) compared to a similar device without the lens array.

The researcher say that such an array can be fully transparent and has no impact on the sharpness of the display. The hexagonal array of 10 um lenses can be fabricated using conventional photolithography methods which are quite cost effective. Such a micro-lens array does not change the actual OLED production process.

Researchers from Yonsei University managed to use a graphene-like 2D material called Molybdenum Disulfide (MoS₂) to create a transistor that can drive flexible OLED displays.

The researcher created a 6x6 OLED pixel array on a 7 mm plastic substrate that is so bendable (1 mm radius) it can be used as a skin sticker as can be seen in the video above.

Researchers from Samsung Electronics and the Ewha Womans University in Korea collaborated in a new study of the degradation in blue phosphorescence OLED materials. This study demonstrate the importance of controlling exciton-induced electron transfer, and more importantly provides strategies for the design of longer-lasting blue PHOLED materials.

The researchers say that the study reveals the charge-neutral generation of polaron pairs (radical ion pairs) by electron transfer from the dopant to host excitons. According to the study, device lifetime correlates linearly with the rate constant for the annihilation of the radical ion pair.

Researchers from Taiwan's National Tsing Hua University (NTHU) developed a new TADF OLED emitter material that maintains its high efficiency at high luminance. The researchers say that this new material is the world's most efficient TADF emitter at high brightness.

The new material is made from two diboron-based molecules, CzDBA and tBuCzDBA. These donoracceptordonor (DAD) type and rod-like compounds concurrently generate TADF with a photoluminescence quantum yield of ~100% and an 84% horizontal dipole ratio in the thin film. The researchers synthesized a green TADF emitter that achieved a a high external quantum efficiency of about 37.8% with an efficiency roll-off of only 0.3% at 1,000 cd/m².

Visionox developed a 7.2" foldable AMOLED display, and has tested its reliability. Visionox says that even after 200,000 folding cycles, the display still showed good reliability. Visionox also performed extensive surface hardness and ball/pen drop tests on this display.

Visionox will discuss the reliability and failure mode analysis of its foldable OLEDs at SID Displayweek 2018 in May - and will also hopefully demonstrate this new display. Visionox performed the tests on a display module that included the AMOLED panel, a touch layer and a thin circular polarizer layer.

Taiwan's AU Optronics (AUO) developed a 13-inch 100 PPI transparent OLED display, specifically for AR applications. This is a highly-transparent display - with 68% transmittance.

AUO 6" transparent OLED prototype (2011)

To achieve such high transparency, AUO optimized the TFT array layer stack, the OLED cathode pattern and the encapsulation. This is the first transparent OLED AUO has developed since 2011. It will discuss this new display at SID Display 2018 - and will hopefully demonstrate it as well.

Researchers from Korea's ETRI (Electronics and Telecommunications Research Institute) developed a flexible OLED panel that use a transparent graphene electrode. ETRI will detail this new graphene-based OLED panel at SID DisplayWeek 2018 in May.

A rigid graphene-based OLED prototype (ETRI 2017)

The researchers produced a "fully operational" 40x40 mm OLED panel that uses the pixelated graphene film as electrodes.