Quantum dots (QD) are emerging as one of the best phosphors for commercial displays due to their narrow full width at half maximum, tunable wavelength, ease for preparation, high quantum efficiency and excellent stability. Specifically, QD based backlight illumination technology is already dominating the high-end TV sets and grows fast to replace tradition phosphors in the wider display market. Intrigued by the great potential of QD, more and more research are dedicated to the electrically driven illumination using QD as the emissive material. Compared to backlight technology, light emitting diodes (QLEDs) delivers brighter, lighter, more flexible and better contrast displays.
 
Dr. Wenyong Liu | Display Expert, TCL

PFS/KSF Technology provides superior performance for efficient red luminescence required in both display applications seeking wider color gamut performance as well as general illumination applications desiring high efficiency with truer color rendering of illuminated areas and objects. With PFS/KSF Phosphors in display devices, LEDs illuminate with a truer saturated red yielding vivid red colors while reducing yellowing of the green pixel emission.  In general illumination, the technology has enabled lighting products with 90CRI and R9>50 at the same/better lumen efficiency as 80CRI products. Moreover, the technology is well suited for high-quality, high-efficient lighting as evaluated with evolving color standards (e.g. TM-30). Significant progress has been made to enable more challenging applications for these fluoride Mn4+  phosphors in terms of both cost and reliability. Today’s use of this technology as well as areas of development, innovation, and expansion for PFS/KSF Phosphor will be discussed. Advancement for green luminescent materials will be shared that build upon the improved color gamut that PFS/KSF technology has enabled.
 
Dr. William Cohen | General Manager, Specialty Materials, Current Lighting Solutions, LLC

An opportunity for a significant increase in luminous efficacy and spectral efficiency of solid-state lighting (SSL) devices can be realized by reducing the amount of light that spills over into the deep red and near-infrared regions (i.e., above 740 nm). Advances in red emitter technology toward narrower emissions peaks has allowed narrow-band (NB) technologies like magnesium-doped potassium fluorosilicate (PFS) phosphor and red quantum dots (QDs) mixed with conventional green phosphors, that were traditionally used in displays, to transition into the more rugged conditions experienced by SSL devices. The long-term performance of these NB red emitter technologies in SSL devices was not well understood, and RTI used accelerated stress testing (AST) to study the long-term behavior of NB red emitter products that use PFS and QD-phosphors. Initial increases of up to 15% in luminous efficacy of radiation (LER) could be achieved using the NB red emitter technology compared to a conventional phosphor-converted LED, and these LER gains were not compromised with aging in elevated ambient temperatures of 75°C. As humidity was introduced into the system (75°C and 75% relative humidity), the NB red emitters experienced significant chromaticity shifts and accelerated decay of luminous flux maintenance. These findings provide direction for future research of NB red emitter technologies and demonstrate that excellent performance can be achieved with both PFS and QD NB technologies in normal indoor environments.
 
Kelley Rountree | Reliability and Exposure Engineer, RTI International

Human Centric Lighting focuses on the photobiological effects of light on the human body, and how those effects can be stimulated and enhanced by high quality LED lighting to enhance human health and well-being. In the area of visible lighting, HCL places an emphasis on the cyan and NIR parts of the spectrum. Quantum dots were first introduced in 2019 to provide record efficacies for general lighting products. These QD materials generally enable the highest quality light at the highest efficacy and are well suited for tailoring a spectrum to a set of desired characteristics while still bringing the highest possible performance. While Human Centric Lighting solutions are growing year-over-year, this talk will cover some of the most prominent HCL designs to date and the technical challenges to introducing QD-enabled HCL components.
 
Dr. Juanita Kurtin | Director of Materials Research, OSRAM Opto Semiconductors

Colour conversion using photoluminescent materials like phosphors, quantum dots and now perovskites is enabling new levels of colour performance and efficiency in displays. Although great improvements are being achieved in LCDs through colour conversion in backlight films, the highest performance and efficiency gains will require colour conversion at the pixel level. This is relevant to almost all emissive displays including OLED and µLED. This talk describes the additional challenges of colour conversion at the pixel level and how Helio is addressing them with new red and green perovskite-based materials. We also discuss the fastest route to adoption for ultimate performance and efficiency enabled by in-pixel colour conversion.
 

Simon Jones | CEO, Helio Display Materials

The trivalent lanthanide ion Eu3+ has the ideal emission spectrum for a red phosphor in solid-state lighting applications. However, the ion has weak absorption in visible part of the spectrum, which makes pumping with blue light-emitting diodes difficult. A potential solution to this problem is sensitization by nonradiative energy transfer between doped nanoparticles. In this presentation, I will go over our efforts to realize interparticle energy transfer to europium-doped nanoparticles experimentally and to understand the parameters that determine the efficiency of the process.
 
Freddy Rabouw, PhD | Professor, Utrecht University

Over the past decades, only a few downconverter materials have emerged as viable for commercial LED applications. Unfortunately, even these best performing phosphors suffer from thermal quenching at high temperatures and ‘droop’ or ‘saturation quenching’ at high light intensities. Despite rigorous optimization efforts, these unwanted effects are often already observed at LED operating conditions, while for even higher power applications only Ce-doped garnets can be used, while no red-emitting material is available. Surprisingly, the mechanisms behind this saturation behavior are often poorly understood. In this talk, I will review three popular commercial LED phosphors: YAG:Ce3+, CASN:Eu2+, and K2SiF6:Mn4+, unravel their saturation mechanisms and discuss the implications of each of these processes for LED applications.
 
Dr. Marie Anne van de Haar | Program Director Materials, Seaborough Research

Nanocrystal semiconductors or quantum dots (QDs) have earned their place as down-convertors for displays since the commercialization of Cd-based QDs in LCDs in the early 2010’s. The benefits in terms of color quality and conversion efficiency have been widely recognized as key selling points. Since then, a shift towards greener, Cd-free materials has been initiated by European RoHS directives that restrict the use of Cd in consumer appliances. This stimulated the development of InP-based QDs, which can nowadays be produced through economical synthesis routes that yield excellent optical properties. In parallel, display technologies have evolved from LCD panels to self-emissive screens with a trend towards smaller and smaller pixel sizes. Technologies such as OLED and in particular microLED, which uses inorganic emitter materials, are seen as key enabling technologies for next generation high-brightness displays. Nevertheless, challenges in scaling pick-and-place processes and in producing highly efficient red and green native microLEDs currently hamper microLED mass production. RoHS-compliant colloidal QDs for on-chip down-conversion provide an attractive and cost-effective alternative for various innovative device architectures that are being developed throughout the microLED ecosystem. For this reason, QustomDot was founded at the start of 2020 to assist the microLED industry and to accelerate the roll-out of QD-microLED displays. At the 2020 edition of the Phosphors & Quantum Dot Industry Forum, QustomDot presented how its technology platform based on InP QD materials yields promising photostability results for red QDs in a mid-power LED package. In this talk, we present progress made in the transition towards relevant film thicknesses for down-conversion at microLED scale (10-30 µm) for both red and green QDs. Challenges such as absorption, solid loading, conversion efficiency and photostability come together in this configuration and we want to provide insights in how we tackle those issues and how we reach 100’s of hours of photostability in this form factor. Questions regarding the viability of InP-based QDs for microLED applications will be discussed and open challenges will be addressed.
 
Willem Walravens | CTO & Founder, QustomDot

We choose the UCr4C4 oxynitride phosphor by adjusting the ratio of precursor between lithium carbonate and lithium nitride and optimizing the synthesis conditions to make the oxynitride phosphors purer. On the other hand, synchrotron radiation X-ray diffraction and neutron powder diffraction are conducted to investigate the detailed structural information. Through the refinement method, we can understand the exact change in the structure. According to the EXAFS spectra, we find that the compositions of the first coordination environment of europium are the same. We deduce the contents of lithium in the second coordination environment and the nephelauxetic effect of europium increase gradually. These effects lead to the spectra redshift. Using temperature-dependent spectroscopy explores the luminescence mechanism of the phosphor. The sample which has the highest quantum efficiency is chosen for LED packaging and obtains better optical performance than Sr[LiAl3N4]:Eu in the device. In this study, ammonium chloride was used as a flux to improve the quantum efficiency of the phosphor as well. Ammonium chloride will increase the content of oxygen in the oxynitride phosphors during the sintering process. Thus, as the flux increases, the emission spectra will cause the blueshift. We can infer the other chemical formula change of oxynitride phosphor by the results of Rietveld refinement. Finally, we can deeply understand the properties of materials and find out their optimized way to increase the application of materials by the structural analysis and the spectroscopic mechanism.
 
Professor Ru-Shi Liu | Professor, Department of Chemistry, National Taiwan University

Industrial cameras capable of imaging objects in the shortwave IR (SWIR) range are attracting increasing interest for applications in food, pharmaceutical, and other industries. While InGaAs sensors gained an early foothold, imaging sensors based on quantum dots (QDs) are introducing unique advantages, such as higher resolutions, wider fields of view, and significantly broader imaging bandwidths. In 2018 SWIR Vision Systems introduced its 2.1 MP Acuros cameras to the industrial imaging market, becoming the first company globally to commercialize high resolution, quantum-dot based image sensors. Since this product introduction, SWIR Vision Systems has continued to advance the performance of its colloidal quantum dot detector architecture. This presentation will provide an overview of our approach to fabricating focal plane arrays, will describe recent results fabricating Vis-SWIR and eSWIR CQD detector arrays, and will show imaging demonstrations of these sensors in a variety of applications.
 
Dr. Ethan Klem | Chief Technology Officer, SWIR Vision Systems

In this talk several fast and mild synthesis routes for luminescent nanoparticles (NPs) are presented. Eu2+ containing NPs of varying host lattices can be obtained even in aqueous solution using Zn as reducing agents for Eu3+. Moreover, its synthesis is also possible in ionic liquids with Eu2+ containing starting materials. In the latter case ionic liquids (e.g. [Bmim][BF4] or [Bmim][PF6]) can also serve as a fluoride source for easy and “green” production of fluoridic NPs. On the other hand NPs of CaWO4:Eu3+, Sm3+ with a persistent afterglow are presented for the first time with the aid of the co-precipitation method in diethylene glycol followed by an annealing step to improve the crystallinity for an intense afterglow. They can be used for bio-imaging and -detection due to the preferred red emission of the doped Eu3+ ions. Another advantage is the possibility to excite the nanoparticles before injection to avoid the problems of low transparency of tissue and autofluorescence of cells.
 
Prof. Dr. Claudia Wickleder | Professor, Inorganic Chemistry, University of Siegen, Germany

Short wave infra-red photodetectors based on colloidal lead sulfide quantum dots (SWIR QDPD) are attractive for the realization of novel image sensors in various fields in the automotive industry, machine vision, surveillance technology, communications and healthcare.
 
Quantum dots possess the characteristic of having a size tunable electronic structure. This means that by fine tuning the size of these nanocrystals a broad range of spectral response can be achieved, while enjoying the benefit of inexpensive, solution-based device fabrication. 
 
In this talk, we will describe the steps of realizing high quality QD-based infrared image sensors based on quantum dot pixel stacks. We will also show how achieving external quantum efficiency above 40% and state-of-the-art pixel pitch below 2 µm leads to high image quality. Finally, we will survey the look ahead for the field of SWIR QDPD.
 
Itai Lieberman, Ph.D. | R&D Team Lead Optical Devices, imec

• Search for nitride phosphors by high-throughput calculations
• Selection rules and discovery of nitride phosphors for laser-driven solid-state lighting
• Design of nitride phosphors with mechaluminescence

Professor Rong-Jun Xie | Professor, College of Materials, Xiamen University (China)

The cost of solar power is currently dominated by the Balance-of-Systems, and only by increasing the efficiency of the solar panels grid parity can be attained on the global level. QD Solar is developing a cost-effective solar solution that has the potential to reach power conversion efficiencies beyond 40%. The technology combines perovskites and colloidal quantum dots in a multi-junction solar cell architecture that has the ability to harvest the full solar spectrum, including the infrared part that conventional solar technologies are transparent to. In this talk we will outline the technology and the considerations for its commercialization.
 
Sjoerd Hoogland | Co-founder, CTO, QD Solar, Inc.

Lanthanide-doped nanoparticles exhibit unique luminescent properties, including a massive Stokes shift, a sharp bandwidth of emission, high resistance to optical blinking, and photobleaching. Uniquely, they can also convert long-wavelength stimulation into short-wavelength emission. These attributes offer the opportunity to develop alternative luminescent labels to organic fluorophores and quantum dots. In recent years, researchers have demonstrated the use of spectral-conversion nanocrystals for many biological applications, such as highly sensitive molecular detection and autofluorescence-free cell imaging. With significant progress made over the past decade, we can now design and fabricate nanoparticles that display tailorable optical properties. In particular, we can generate a wealth of color output under single-wavelength excitation by rational control of different combinations of dopants and dopant concentration. By incorporating a set of lanthanide ions at defined concentrations into different layers of a core-shell structure, we have expanded the emission spectra of the particles to cover almost the entire visible region, which is unavailable to conventional bulk phosphors. In this talk, I will highlight recent advances in the broad utility of lanthanide-based nanocrystals for multimodal imaging, bio-detection, therapy, display, X-ray scintillation and nanophotonics.
 
Xiaogang Liu, PhD | Professor, Department of Chemistry, National University of Singapore

In recent years, quantum dots (QDs) have gained interest as narrowband emitters for displays, but have traditionally suffered from reliability issues, high manufacturing costs, and toxicity concerns, which prevent them from being incorporated into products beyond displays. At UbiQD, local advanced materials company and LANL-spinoff, we are on the path to making QDs ubiquitous with a new QD composition that is intrinsically more stable, lower-cost, and avoids toxic compounds. We are bringing to market QD-enhanced polymers and glass for spectrum-optimized greenhouses and solar windows.
 
Hunter McDaniel, Ph.D. | Founder and CEO, UbiQD, LLC