Displays

Micro-LED (also known as mLED or µLED) is a display technology based on miniature LED devices that are used to directly create color pixels. Micro-LED displays are highly promising and have the potential to create efficient and great looking flexible displays, which could challenge even the most impressive high-end OLED displays. Micro LEDs are attracting significant attention as next-generation displays owing to their desirable characteristics such as low power consumption, high contrast ratio, high brightness, fast response speed, and long life span.

Perovskite materials can benefit the MicroLED industry in two ways: as materials for color conversion (using perovskite-based QDs) and in perovskite-based LED emitters. Much R&D work is taking place on both these fronts, and interest seems to be growing.

Researchers at Linköping University, Nanjing University and NanjingTech have developed a multifunctional display that uses photo-responsive metal halide perovskite LEDs as pixels. The perovskite LED display can be simultaneously used as a touch screen, ambient light sensor and image sensor (including for fingerprint drawing) without integrating any additional sensors. The light-to-electricity conversion efficiency of the pixels also allow the display to act as a photovoltaic device that can charge the equipment.

Illustration of functions realized by the multifunctional display. Image from Nature Electronics

This is a step forward compared to current display screens, which are typically only used for information display, but can have a range of different sensors integrated into them for functions such as touch control, ambient light sensing and fingerprint sensing. According to the team, photo-responsive light-emitting diodes (LEDs), which can display information and respond to light excitation, could be used to develop future ultra-thin and large screen-to-body ratio screens. However, photo-response is difficult to achieve with conventional display technologies. 

Researchers from China's Xiamen University, Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Yang Ming Chiao Tung University and Hon Hai Research Institute have reported a self-polarizing RGB device utilizing semipolar micro-LEDs and perovskite-in-polymer films aimed at improving backlight applications.

Structure of an LCD based on semipolar blue μLEDs excite anisotropic perovskite NCs as backlight. Image from Opto-Electronic Advances

In backlighting systems for LCDs, conventional red, green, and blue (RGB) light sources that lack polarization properties can result in a significant optical loss of up to 50% when passing through a polarizer. To address this inefficiency and optimize energy utilization, the scientists developed a high-performance device designed for RGB polarized emissions. The device uses an array of semipolar blue µLEDs with inherent polarization capabilities, coupled with mechanically stretched films of green-emitting CsPbBr₃ nanorods and red-emitting CsPbI₃-Cs₄PbI₆ hybrid nanocrystals. 

Perovskite nanocrystals (PNCs) have considerable potential as next-generation display materials thanks to their excellent photoluminescence quantum yield (PLQY), wide color gamut, and narrow emission bandwidth. However, due to their weak stability against solvents, their patterning remains a challenge. In a recent study, researchers at Ajou University, Hanyang University, Sungkyunkwan University, Macquarie University and Kongju National University developed functional organic ligands (AzL1-Th and AzL2-Th) for the fine pixelation of perovskite nanocrystal (PNC) displays. 

Functional ligands containing photocurable azide moieties exhibit good charge transport properties and fast and efficient photocrosslinking performance, while maintaining a high PLQY. The team successfully demonstrated the crosslinked PNC light emitting diodes using AzL1-Th. The results suggest the high potential of photocurable ligands for the micro-patterning of PNC films without film damages.

Perovskite-Info is proud to announce an update to our Perovskite for the Display Industry Market Report. This market report, brought to you by the world's leading perovskite and OLED industry experts, is a comprehensive guide to next-generation perovskite-based solutions for the display industry that enable efficient, low cost and high-quality display devices. The report is now updated to February 2024, with all the latest commercial and research activity. This was a major version, with over 15 updates, new companies and new technologies covered.

Reading this report, you'll learn all about:

• Perovskite materials and their properties
• Perovskite applications in the display industry
• Perovskite QDs for color conversion
• Prominent perovskite display related research activities

The report also provides a list of perovskite display companies, datasheets and brochures of pQD film solutions, an introduction to perovskite materials and processes, an introduction to emerging display technologies and more.

Researchers at Lawrence Berkeley National Laboratory (Berkeley Lab), led by Prof. Peidong Yang, have developed a new 3D printing ink based on perovskite materials, that exhibits near 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:

Eiffel Tower luminescent structures, made from 3D-printed supramolecular ink (Berkeley Lab)
 

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.

A team of researchers, led by Maksym Kovalenko at ETH Zurich and Empa, working in collaboration with scientists from the U.S. and Ukraine, recently demonstrated how the promising properties of perovskite quantum dots can be improved further. They used chemical methods for surface treatment and quantum mechanical effects that had never before been observed in perovskite quantum dots. 

Perovskite quantum dots can be mixed with liquids to form a dispersion, which makes them easy to process. Moreover, their special optical properties make them shine more brightly than many other quantum dots. They can also be produced more cheaply, which makes them interesting for applications in displays, for instance. On top of all this, the newly developed phospholipid molecules create a protective layer around the perovskite nanocrystal and make it possible to disperse it in non-aqueous solutions. They also ensure that the quantum dot emits photons more continuously. 

Swiss additive manufacturing startup Scrona and Avantama, developer and manufacturer of high-tech materials for electronics, have jointly announced that they have successfully processed high-performance perovskite quantum dot (QD) ink using Scrona's electrohydrodynamic (EHD) inkjet printing. 

This collaboration combines the benefits of the inkjet process with high-patterning resolution to drive a new generation of efficient and cost effective MicroLED displays, while also increasing color purity and brightness, and improving overall pixel production tact time. 

Researchers at Seoul National University and Korea Advanced Institute of Science and Technology (KAIST) have developed highly efficient tandem perovskite light-emitting diodes (PeLEDs). This advancement may expedite the commercialization of perovskite light-emitting materials in next-generation display technologies.

The Ministry of Science and ICT (MSIT) announced that the team, led by Professor Lee Tae-woo from Seoul National University’s College of Engineering, has successfully created a high-efficiency and long-life hybrid tandem light-emitting device. This device combines metal halide perovskites with organic light-emitting diodes.

Researchers at Yonsei University and Korea University have integrated perovskite films with two-dimensional electronics to address current obstacles that hinder the commercialization of perovskite LEDs (PeLEDs). 

The scientists developed centimeter-scale integrated PeLED displays achieving key metrics on par or better than existing standards. This work suggests the potential transition of PeLEDs from lab concept to next-generation commercial displays.