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Colloidal quantum dots (QDs) have been known to be the best candidates for emissive materials owing to their unique optical properties including high color purity and quantum efficiency. Cd-based QDs like CdSe, CdS, and CdTe have been extensively studied and their synthesis and application methods are very well developed, despite their potential harmful effects on health and the environment. Instead, InP QDs have been considered as the best alternative because of their band gaps corresponding to visible light as well as their relatively low toxicity. However, they could be easily oxidized to InPOx and have weak electronic tolerance to surface defects due to their relatively high covalent character. In this presentation, I will talk InP-based QDs showing almost unity photoluminescence quantum efficiency and long-term stability on high power blue irradiation. Based on this superior optical properties, the QDs could be applied for the color conversion pixels on blue OLED display.

Micro LED display has been considered as the next generation self-emitting display technology, because LED has been known as better luminance efficiency, durability & reliability than OLED. Lots of companies have been suggested about the key technologies of the manufacturing micro LED chips, intermediate process, manufacturing backplane, mass transferring, chip bonding & repair process. But, in this moment, there are only a few applications with micro LED display yet due to significant technical issues. In this speech, we will check the current status, technical issues & market forecast of micro LED display technology. Especially, we will review these agenda with analyzing the recent studies, prototypes & products from lots of companies. So, we can suggest that how the micro LED display should be developed and focused in the future.

Issues and experience of mini LED adapted into the display stepping to address micro LED display outlook.

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The roadmaps for MicroLED sizes are clearly indicating that future manufacturing technologies needs to be prepared for sizes down to 5 µm. Some current technologies adapted from MiniLED production are capable to process today´s MicroLED´s of around 50 µm but running into yield and basic challenges for the next generations.
Lasers are a key enabling manufacturing technology. This is because lasers have an unrivalled ability to yield smaller and more precise features at high throughput, and to work without physically damaging or overheating delicate parts.
Our presented laser processing technologies are capable to process very small MicroLED´s either from the growth (EPI) wafer, called the Laser Lift-off (LLO) or the mass transfer from temporary carriers. This is a future-proof technology approach and help MicroLED display makers to invest once, adapt a technology for the next years, and transfer the processing technologies into mass production.
We will present our latest information and results about laser processing solutions for MicroLED displays – from very small to very large displays.

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With the growing demand for ever-smaller devices, such as mini- and microLED displays with higher resolution rates, there is an unstoppable trend towards miniaturisation of components. High-speed, mass-production of these electronics is getting more and more difficult, because the handling and accurate placement of these tiny components is very challenging. Each component needs to be carefully selected, transferred and then accurately placed and assembled with interconnects – all at lightning speeds. As conventional industrial equipment fail to deposit ultrafine pattens of die attach material and handle such tiny components at required high rates, this calls for development of alternative high-throughput assembly technologies.

Holst Centre is continually pushing the boundaries of hybrid printed electronics technologies to open new frontiers and enable new promising applications. Leveraging on over a decade-long experience in development and maturing of Laser Induced Forward Transfer (LIFT) technology and bringing it to the next level, we have developed a new laser-assisted printing technology – Volume-Controlled Laser Printing (VCLP) – capable of high-throughput deposition of ultrafine interconnects, such as conductive adhesives and solder pastes, from structured carrier plated covered with a proprietary permanent release layer. At Holst Centre we believe that high-throughput deposition of ultrafine interconnect patterns using VCLP technology opens up new possibilities for various applications, particularly, flip chip integration of micro-LED displays.

To complement VCLP interconnect printing technology and complete high-throughput integration of microcomponents, at Holst Centre we have developed another laser-assisted technology targeted to selectively and accurately transfer microcomponents from carrier wafers populated with high-density arrays of microcomponents. The technology has no fundamental limits to scale down to transfer of sub-10 µm microcomponents with dicing street as narrow as 5 µm. We have already demonstrated that our innovative and proprietary release stack developed at Holst Centre enables high-throughput, fast and well-controlled transfer of microcomponents, as small as 40x40x10 µm3 with 20 µm dicing street.

GaN microled is the key display technology for the next generation AR/MR glasses and Metaverse. Microled arrays driven by CMOS circuits are needed for GaN microdisplays and large area displays.
Several technologies can be used to hybridize the two parts. We will review the challenges for their fabrication, show solution provided such as microtube technology and recent results with hybrid bonding.

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We have developed a versatile, flexible and sustainable printing process to print micrometre semiconductor/optoelectronic devices into a surface to create functional surfaces such as displays at the yield and throughput required for such products. In addition, we have developed a self-aligned process that can enable the ultimate displays needed for augmented reality (super high brightness, ultra-high resolution, full colour, low power, and very compact).

The cartridge-based printing process is developed to offer a simple, scalable tool with faster throughput, higher yield, and high uniformity. This solution does not require picking microLED for every transfer and does not require a laser for releasing microLEDs into the display substrate. As a result, it benefits from simple tools that can be scaled to a large area and offer high throughput due to simple process steps.

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Tight pitch integration of compound semiconductor with advanced node CMOS like in microLED displays requires a full wafer level monolithic approach in 300mm. At pitches below 5um, the CMOS bonding is at the center and cannot be considered as an afterthought of a great LED process. Here we show a 9150ppi µLED process-flow with backplane integration that is realized in a 300mm CMOS pilot line using standard volume manufacturing equipment with a similar integration scheme as is done for 3D-stacked backside illuminated imager (BSI). This includes the realization of wafer level optics for beam-shaping. The achieved brightness exceeds 1Mnits. We discuss the inter-dependency of pitch vs manufacturing yield including epi-defectivity and epi-uniformity.

Ultra-Precise Deposition (UPD) is an additive manufacturing technique for fabricating conductive and non-conductive features at a micrometer scale. The process does not require an electric field, the deposition can be made on any substrate (conductive and non-conductive, planar and 3D) and materials with viscosities up to 1 000 00 cP can be printed in full resolution range. The combination of unique features can be used for fabricating next-generation OLED, MicroLED, and QD-LED displays.
Due to precise pressure control and the system's design, UPD allows depositing material with femtoliter precision. Together with the possibility to deposit materials with viscosities up to 1 000 000 cP and high solid content the UPD technology can be used for depositing conductive microdots below 10 µm in diameter and a very high aspect ratio for flip-chip application (for example micro-LED assembly).
UPD technology can also be used for the deposition of color-conversion layers based on quantum dots. We demonstrated technology that allows direct deposition of Quantum Dots material, simplifying the whole process and reducing the overall manufacturing cost. Moreover, it increases resolution: microdots currently obtained on the market usually have about 50 μm, the minimum is 20 μm – while we demonstrated with UPD technology dots with a diameter of even less than 5 μm. Compared to other digital additive manufacturing techniques like inkjet and EHD, UPD technology allows the deposit of high uniformity and repeatability structures with the use of inks with a higher concentration of QDs. This, according to Beer’s law, directly affects light absorption by the QDs. The combination of unique capabilities of the UPD printing method provides the solution for efficient fabrication of QD color conversion for next-generation Micro-LED displays.

Morphotonics has set the standard in the replication of structures that range from 500 microns down to 50 nanometers on large areas of greater than 1-meter square. Our Roll-to-Plate (R2P) technology and
equipment not only enable manufacturing scalability (thus lowering unit costs) but also offer high replication fidelity down to picometer-scale. R2P technology is already being used to manufacture optical components inside commercial displays currently on the market. Additionally, R2P-based waveguide manufacturing is a strong candidate for addressing the high-volume manufacturing needs of emerging Augmented Reality (AR) glasses.
We have replicated many Micro Lens Array (MLA) optical structures for a variety of applications. Using aligned micro-optics, we can address the light collimation challenges that Mini- and MicroLEDs face to
achieve higher energy efficiency and lower power consumption. We are currently developing equipment that will significantly improve the overlay accuracy down to ±5 microns, allowing us to address the optical collimation needs of MicroLED displays.
Consequently, we are exploring several ways to address this emerging segment of the display market inthe near future.

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MicroLED is still mostly in the process of transitioning from the lab to high-volume manufacturing. MiniLEDs, on the other hand, have already attracted more than $15 billion of investment for manufacturing infrastructure and are commonly used in high volume consumer products as well as in B2B, direct view LED displays.
MiniLEDs backlights can supercharge LCD panels, allowing them to compete against OLEDs in high-end, high-added value consumer markets. In industrial markets, narrow pixel pitch miniLED displays are growing at a 24% CAGR.
With OLED continuously improving, is the window of opportunity already closing for miniLED backlights? Will miniLED dominate in direct view LED displays and converge with microLEDs to break into the consumer market?
This presentation will discuss miniLED markets, applications, supply chain as well as technology trends based on device teardowns and performance measurements conducted by Yole Group.