Technical / research

Researchers from Sungkyunkwan University developed a source material for the inorganic hole transport layer of QD-EL devices. The researchers say that the new material significantly enhances the brightness and stability of emissive QD displays.

The researchers say that currently used organic HTL materials suffer from low conductivity and thermal instability. The new material is a standard HTL doped by defect-controlled nickel oxide-magnesium oxide alloy and treated with magnesium hydroxide. Using the new material, the EQE of the QD-EL device increased to 16.4%. The doping and treatment lowered the hole conductivity of the hole transport layer and suppressed the hole extraction process from within the quantum dots, thereby enhancing the device efficiency to a level comparable to existing technologies.

Researchers from China's Southern University of Science and Technology, by simultaneously measuring the electroluminescence-photoluminescence, have identified the presence of leakage electrons in QD-EL devices, which leads to the discrepancy of the electroluminescence and the photoluminescence roll-off.

The researchers then developed a single photon counting technique, the enables them to detect the weak photon signals and thus provides a means to visualize the electron transport paths at different voltages. By reducing the amount of leakage electrons, the researchers developed a QD-EL device with an internal power conversion efficiency of over 98%.

Researchers at Daegu Gyeongbuk Institute of Science and Technology (DGIST), Ulsan National Institute of Science and Technology (UNIST), and the Institute for Basic Science (IBS) have developed a new method, called double-layer dry transfer printing, to create highly efficiency QD-EL displays.

The researchers say that with the double-layer dry transfer printing technique, the light-emitting and electron-transferring layers of the device can be transferred onto a substrate simultaneously, which reduces interfacial resistance in the device, which facilitates electron injection and the control of leakage charge transport during the fabrication process. The researchers, by minimizing the leakage current, managed to increase the EQE of the QLED device to 23.3%, up from around 5% that is achieved with normal dry transfer printing. 

Researchers from Korea's Institute for Basic Science, led by Professor KIM Dae-Hyeong, published a new article in Nature that details intrinsically stretchable quantum dot LEDs. 

The researchers say that using current technology, making stretchable light-emitting devices results in poor luminous performance. The researchers now produced the intrinsically stretchable QD-LEDs using a mechanically soft and stretchable emissive layer consisting of a ternary nanocomposite of colloidal quantum dots, an elastomeric polymer and a charge transport polymer.

The prestigious Nobel Chemistry prize for 2023 was awarded to Moungi Bawendi, Louis Brus and Aleksey Ekimov, the three scientists that discovered quantum dots.  The Nobel prize is worth 11 million Swedish crowns (around $1 million), and will be split between the 3 winners.

The Royal Swedish Academy of Sciences, that awards the prize, stated that "Researchers believe that in the future they (QDs) could contribute to flexible electronics, tiny sensors, thinner solar cells and encrypted quantum communication".

Researchers from MIT have devised a new method to precisely assemble arrays of quantum rods, using scaffolds made of folded DNA. Using this method, the orientation of the rods can be controlled, which is a key factor in determining the polarization of light emitted by the quantum rods array.

The method starts by attaching the quantum rods to diamond-shaped DNA origami structures, built at an exact size required by the device. The structures are then attached to a surface, where they fit together "like puzzle pieces". 

Researchers from Samsung Display, led by Changhee Lee, developed an all-inkjet-printed 12.4" full color 182 PPI EL-QD display, that offers improved performance.

The researchers say that by controlling carrier transport properties and charge balance through ligand exchange in QDs and ZnMgO surface, they were able to create this display that has a potential for low cost and material-consumption-efficient display manufacturing. The researchers will disclose the paper at SID Displayweek 2023 next week.

Researchers from Kyung Hee University and the Korean Institute of Science and Technology have demonstrated that a low-temperature processed PTAA hole transport layer (HTL) can improve the performance of flexible light emitting quantum dots (QD-EL, or QLEDs) - produced on plastic substrate.

The researchers say that using a low-temperature process ensures that the flexible substrate is not deformed. Such QLED devices suffer from low performance compared to glass based devices that use optimal PTAA HTLs, but the new process and materials improve the flexible devices closer to glass based ones.

Researchers led by a team from the University of Chicago developed a new method to synthesize large-area ("giant") light-emitting QDs that emit light following an exciton state for over 500 nanoseconds, which is a new record.

The new QDs are based on a structure that allows the electrons to focus on holes within a core or shell heterostructure. This is performed by tuning the charge electron to the kinetic energy of a parabolic potential energy surface.

Developing blue-emitting quantum dots is highly challenging, and researchers from the University of Tokyo says that using a new bottom-up design strategy and self-organizing chemistry they have managed to create a high purity blue-emitting QD material (with a narrow emission spectrum).

The new QDs are made from special chemical composition that combines both organic and inorganic substances, such as lead perovskite, malic acid, and oleylamine. The materials self-aligned into a cube of 64 lead atoms. The lead researcher, Professor Eiichi Nakamura, says that "it took over a year of methodically trying different things to find that malic acid was a key piece of our chemical puzzle".