Technical / Research

Researchers from Korea's Hanyang University, Yonsei University, and Sogang University have jointly developed new hole transport materials and processes that enable the fabrication of ultra high definition OLED microdisplays - achieving over 10,000 PPI.

The researchers explain that one of the problems with ultra-high-density OLED displays is that as the distance between pixels approaches the micrometer level, electrical signal interference which leads to light leakage from closeby pixels and a decrease in color fidelity. This leakage between subpixels occurs because the hole transport layer that facilitates the movement of holes is shared among the pixels that form the display.

Researchers from the University of Manchester and the University of Cambridge, led by Prof. Alexander Romanov, have discovered a new class of OLED host material, that is highly efficient and also is very easy to synthesize, and thus could be very cheap to produce.

Compared with PPBI, one of the popular hosts for blue OLEDs, the new 1,3,5-oxadiazines (NON) materials possess the same or improved characteristics, such as wide band gap and high triplet state energy up to 3.3 eV, whilst costing 100 times less after sublimation. Dr Hwan-Hee Cho from Optoelectronics Group at the University of Cambridge performed the first tests in deep-blue OLED architecture to demonstrate that NON-hosts can result in up to 21% EQE at practical brightness with CIE colour coordinates (0.17, 0.16) – outperforming other commonly used hosts in the same device stack. NON-host materials and their further derivatives have a strong potential for the OLED community to unlock high-performance electronic displays.

Researchers from Hasselt University, led by Prof. Wim Deferme, have discovered that adding an interface layer at the electron injection layer (EIL) can improve the efficiency of OLED devices. The researchers explain that the materials  improve the mobility of electrons towards the recombination layer, and so enhance the efficiency of he light emission. Metal chlorides lead up to an increase of 50% in efficiency as compared to device stacks without the interface layer.

The researchers tested several materials, including RbCl, CsCl, NaCl, and KCl as interfacial layers in OLED architectures, and has seen that these led to a substantial reduction in the potential energy barrier between the electron injection layer (EIL) and the aluminum (Al) electrode, accompanied by significant enhancements in irradiance. These enhancements in the performance of the OLEDs include a lower turn-on voltage (almost 50% reduction by addition of the RbCl layer), a higher electroluminescence intensity (25% higher than the reference device for the RbCl-based OLED), improved current density, enhanced operational stability compared to the reference devices, and enhanced external quantum efficiency (EQE) (20% higher for NaCl-based OLED).

Researchers from the Korea 's SNU, KAIST and KIMM developed a new lift-off process for flexible OLED displays, based on graphene. The researchers term the new method GLLO, or Graphene Laser Lift Off.

The researchers placed a single-layer CVD graphene film between the polyimide film and the glass carrier. The graphene, with its ability to absorb ultra-violet light and distribute heat laterally, enables a clean lift-off without any wrinkles or residues. Using the GLLO method, the researchers successfully separated 2.9 μm thick ultrathin PI substrates without any mechanical damage or carbon residue left behind. In contrast, traditional methods left the substrates wrinkled and the glass carriers unusable due to stubborn residues. This breakthrough has far-reaching implications for stretchable electronics and wearable devices.

The Indian Institute of Technology Madras (IIT Madras) has inaugurated a new research center dedicated for the development of AMOLED technologies. The new AMOLED Research Centre (ARC) is a national centre of excellent that is funded by the Government's Ministry of Electronics and Information Technology (MeitY), by the Indian Defence Research and Development Organisation (DRDO), and Tata Sons.

The goal of this new center is to help India's display manufacturing industry. It will focus on AMOLED displays for wearables, smartphones, and tablets. Researchers at the ARC will also engage in research into OLED TVs, OLED lighting and OPVs.

Researchers from the University of Science and Technology of China (USTC and the Beijing Information Science and Technology University (BISTU), have developed a new strategy for the design of deep red MR-TADF OLED emitters, that offers high efficiency, good color emission and long lifetimes. 

The researchers report they have developed a new deep red (0.657,0343 CIE) OLED emitter material that achieves high efficiency, over 43% EQE, which they say is the most efficient MR-TADF red emitter.

Researchers from the the University of Michigan developed a new class of phosphorescence OLED emitters that do not contain heavy metals. The metal was replaced with a new hybrid material. The researchers collaborated with colleagues from Inha University, and Sungkyunkwan University.

In current phosphorescence  OLEDs, the emitters include a heavy metal, in most cases either iridium or platinum. These heavy metals generate a magnetic field that forces the same spin direction excited electron to turn quickly, resulting in faster light emission as it returns to its ground state. The researchers replaced the heavy metal with a 2D layer of molybdenum and sulfur near a similarly thin layer of the organic light emitting material, achieving the same effect by physical proximity without any chemical bonding. 

Researchers from the University of St Andrews, led by Prof. Ifor Samuel, have designed an OLED based communication device that achieves a record data rate of 3.2Gbps.

To realize this achievement, the researchers developed high-speed red, green and blue emitting OLED devices, on a single substrate. Using wavelength division multiplexing (WDM), the three OLED devices are emitting at the same time. By selecting fluorescent materials with nanosecond emission lifetimes and little overlap between their emission spectra, the researchers achieved a -6b dB electrical bandwidth of over 100 Mhz. 

Researchers from Durham University have used a unique molecule to create TADF emitters with better triplet harvesting, and thus extended lifetime. The fused indolocarbazole-phthalimide molecules offer rigidly planar charge-transfer and can maintain their stability and efficiency over time, even in high-stress conditions.

The researchers say that the new molecules break all our current ideas about excited states in OLED emitters and the researchers developed a new model linking molecular bonding patterns leading to the breaking of molecular pi-conjugation in the excited state. 

Researchers at Korea's Gachon University, in collaboration with InnoQD and researchers from Chungbuk National University, have developed a new QD-OLED patch that can encourage hair growth. The patch can also measure heart rate at the same time.

The researchers used a flexible OLED device, and covered it with quantum dots that emit near-infrared (NIR) light. The OLED device is a tandem blue OLED device, that offers a high light output. The researchers say that when attached to the head, the patch encourages hair collicle cell growth, with a measured improvement of 23% in hair growth.