Technical / Research - Page 5

Researchers Durham University, led by Professor Andrew Monkman, discover new OLED emitters that offer high performance in a hyperfluorescence emission system. The main new material, a molecule called ACRSA, was found to triple the efficiency of hyperfluorescence OLED devices.

These OLED emitters aren't actually new - they were studied years ago, but were found to be poor emitters. That was true when used as OLED emitters, but when used in a hyperfluorescence system (which combines both fluorescent and TADF emitters), these were surprisingly efficient. The ACRSA emits a green emission, but deep blue light emission can be achieved by transferring ACRSA's energy to a blue terminal emitter. This approach reduces exciton energy compared to direct blue emission in devices, allowing more stable, longer-lasting blue OLEDs.

Researchers at Lawrence Berkeley National Laboratory (Berkeley Lab), led by Prof. Peidong Yang, developed a new 3D printing ink based on perovskite materials, that exhibits unity photoluminescence quantum yield (PLQY). Interestingly, as it is a 3D printable ink, it is possible to create luminescent objects from it, as seen in the image below:

The researchers brand the new ink as 'supramolecular ink', and say it is produced without any rare metals. It is a combination of several powders containing hafnium (Hf) and zirconium (Zr), and is made at room temperatures. In a process called supramolecular assembly, tiny molecular building block structures are self-assembled within the ink. These supramolecular structures enable the material to achieve stable and high-purity synthesis at low temperatures.

Toray Research Center (TRC) has launched a new open online webinar focused on OLED inspection and analysis technologies. TRC, who supplies technical analysis and support for R&D and manufacturing, invites you to attend the online lectures at no cost, to get a deeper understanding on OLED inspection and analysis, and how to achieve higher performance displays. The webinar recordings are accessible until February 15.

The webinar include four presentations:

• Identification of Trace Impurities Using High-Resolution Mass Spectrometry (Toward High-Quality OLED Panels)
• Analysis of Small Molecule OLED Layers in Solution Process and Vacuum Deposition Process
• Moisture Diffusion Evaluation in Encapsulant
• Analysis of QD sheet (Quantum Dot Enhancement Film)

The first presentation, titled Identification of Trace Impurities Using High-Resolution Mass Spectrometry (Toward High-Quality OLED Panels), details examples of possible degradation in OLED devices that lead to performance reduction. In this presentation, TRC discusses the role of analysis, the advantages of high mass resolution, different evaluation techniques and how it can help developers increase the performance of OLED displays.

In 2023, we reported on research conducted at Germany's Max Planck Institute, led by Prof. Paul W.M. Blom, that looks into single-layer OLED devices. In such devices, a single TADF OLED emitter layer is sandwiched between two electrode - a much simpler design compared to commercial OLED devices that use multilayer stacks, sometimes with 10 or more layers. The researchers the the MPI say that in fact it is possible to develop highly efficient OLEDs with just the TADF emitter - and have demonstrated 100% IQE single-layer devices, with an EQE of 27.7%. 

Prof. Blom's group continues to improve its single-layer TADF OLED device, and have now reported that by employing a recently developed trap-free large band gap material as a host for the DMAC-BP OLED emitter, a nearly balanced charge transport is achieved. The device achieves a record power efficiency for DMAC-BP TADF OLEDs of 82 lm/W - surpassing  the best reported multilayer power efficiencies of 52.9–59 lm/W. This is due to the lower operating voltage. The single-layer device reaches an external quantum efficiency (EQE) of 19.6%, which is only slightly lower than the reported EQEs of 18.9–21% for multilayer devices. In addition to the high power efficiency, the operational stability is greatly improved compared to multilayer devices and the use of conventional host materials in combination with DMAC-BP as an emitter.

Researchers from Japan's Chiba University developed a new method to deposit thin OLED layers that achieves controllable molecular arrangement - that can be used to increase the efficiency and lifetime of OLED devices.

The method, called intermittent deposition, uses pauses in deposition and changes in deposition conditions to invert the orientation of the organic molecules, thus achieving high control over the resulting films. The researchers built on a tool called Rotary Kelvin Probe (RKP) that is used to measure the surface potential during and after the deposition in real-time. The new approach of intermittent deposition created a relaxed and stable surface layer with controllable polarization. 

Researchers from the University of Michigan developed a new OLED emitter system, based on a blue phosphorescence emitter, based on the polariton-enhanced Purcell effect. This new emitter systems offers high stability and high efficiency. 

The basic idea is to start with a light-blue (cyan) phosphorescence emitter (which offers a longer lifetime than a deep blue emitter), and placing it between two mirrors. The distance between the mirrors is controlled so that only deep blue light waves persist and are emitter from the mirror chamber. The researchers also tuned the optical properties of the OLED stack to the adjacent metal electrode which introduced a new quantum mechanical state called a plasmon-exciton-polariton, or PEP. This new state allows the organic material to emit light very fast, thus even further increasing the lifetime by decreasing the opportunity for excited states to collide and destroy the light-emitting material.

Researchers from Korea's Dongguk University developed a new green phosphorescent OLED emitter based on a manganese complex called MnBz. The green MnBz emitter offers high brightness and efficiency and low-cost fabrication without any heavy metals. The green emitter was also used to create a warm-white OLED device.

The new emitter is based on a a zero-dimensional manganese (Mn)-based complexes, produced via solution processing. The green phosphorescent OLED offers a record-breaking quantum efficiency of 11.42% and current efficiency of 56.84 cd A^-1. 

Toray Research Center (TRC) has launched its open online webinar focused on OLED technologies. TRC, who supplies technical analysis and support for R&D and manufacturing, invites you to attend the online lectures at no cost, to get a deeper understanding on OLED technologies and analysis of OLED devices. The webinar recordings are now accessible for two weeks.

The first lecture, titled 'current analytical techniques for displays', will focus on current techniques used for OLED analysis, including OLED layers observation by high-contrast STEM, OLED layer construction analysis by GCIB-TOF-SIMS and TOF-SIMS MS/MS and quantification analysis using LC/CAD. The same lecture will also discuss recent topics in analysis technology, including the degradation analysis of QD devices.

On November 2nd 2023, Toray Research Center (TRC) will share an open online webinar focused on OLED technologies. TRC, who supplies technical analysis and support for R&D and manufacturing, invites you to attend the online lectures at no cost, to get a deeper understanding on OLED technologies and analysis of OLED devices. The webinar recordings will be accessible from November 2nd, for two weeks.

The first lecture, titled 'current analytical techniques for displays', will focus on current techniques used for OLED analysis, including OLED layers observation by high-contrast STEM, OLED layer construction analysis by GCIB-TOF-SIMS and TOF-SIMS MS/MS and quantification analysis using LC/CAD. The same lecture will also discuss recent topics in analysis technology, including the degradation analysis of QD devices.

Dr. Kou Yoshida and Dr. Junyi Gong, from the University of St Andrews, working with Prof. Ifor Samuel and Prof. Graham Turnbull, have developed an integrated organic laser device, based on an electrically-pumped laser.

In this work, the researchers developed and electrically driven organic electronic laser, with a narrow emission spectrum and the formation of a laser beam above the threshold. The researchers have shown that indirect electrical pumping by an OLED is a very effective way of realizing an electrically driven organic semiconductor laser.