Colloidal Nanocrystals for Quality Lighting and Displays: Milestones and Recent Developments

Total Page:16

File Type:pdf, Size:1020Kb

Colloidal Nanocrystals for Quality Lighting and Displays: Milestones and Recent Developments Nanophotonics 2016; 5 (1):74–95 Special Issue Article Open Access Smart nanophotonics for renewable energy and sustainability Talha Erdem and Hilmi Volkan Demir* Colloidal nanocrystals for quality lighting and displays: milestones and recent developments DOI 10.1515/nanoph-2016-0009 Received October 1, 2015; accepted October 1, 2015 1 Introduction Abstract: Recent advances in colloidal synthesis of Since the end of the 20th century, we have been witnessing nanocrystals have enabled high-quality high-efficiency the advance of electronics and photonics in a mutual re- light-emitting diodes, displays with significantly broader lation. The developments in one field clearly contribute to color gamut, and optically-pumped lasers spanning the further developments in the other. An important binding whole visible regime. Here we review these colloidal plat- force of this relation has been the research on emerging forms covering the milestone studies together with re- materials including in all disciplines of materials science, cent developments. In the review, we focus on the devices chemistry, physics, and electrical engineering. Thanks to made of colloidal quantum dots (nanocrystals), colloidal these multidisciplinary efforts at a global scale, today we quantum rods (nanorods), and colloidal quantum wells have very sophisticated optoelectronic devices, for exam- (nanoplatelets) as well as those of solution processed per- ple, luminaries, displays, sensors, imaging tools, etc. Es- ovskites and phosphor nanocrystals. The review starts pecially within the last two decades, significant contribu- with an introduction to colloidal nanocrystal photonics tions to photonics have come from the science and tech- emphasizing the importance of colloidal materials for nology of semiconductor colloids [1–6] leading to today’s light-emitting devices. Subsequently, we continue with the commercial devices [7, 8] made of colloidal semiconduc- summary of important reports on light-emitting diodes, tor nanoparticles. Some of the attractive features of these in which colloids are used as the color converters and colloidal materials can be listed as their high quantum ef- then as the emissive layers in electroluminescent devices. ficiencies, precisely controllable emission colors, narrow Also, we review the developments in color enrichment and emission bandwidths, large absorption cross sections, im- electroluminescent displays. Next, we present a summary proved stabilities, cost-effectiveness, and abundance [9]. of important reports on the lasing of colloidal semicon- Among the devices involving colloidal materials, in this ductors. Finally, we summarize and conclude the review review we focus on the light-emitting devices, in partic- presenting a future outlook. ular, light-emitting diodes (LEDs), displays, and lasers in which colloidal semiconductor quantum dots (QDs), rods (also known as nanorods), and wells (also known as nanoplatelets, NPLs) along with perovskites and phos- phor nanocrystals are utilized. Here, we summarize early milestone works and recent important advancements on these topics for each device. Talha Erdem: Department of Electrical and Electronics Engineer- LEDs were one of the first devices utilizing colloidal ing, Department of Physics, Institute of Materials Science and Nan- semiconductor nanoparticles, which offer spectral tuning otechnology, and UNAM-National Nanotechnology Research Center, in white light generation along with high efficiencies and Bilkent, Ankara Turkey 06800 high quality lighting for indoor [10] and outdoor [11] light- *Corresponding Author: Hilmi Volkan Demir: Department of ing applications. In LEDs, colloidal nanoparticles were Electrical and Electronics Engineering, Department of Physics, Insti- tute of Materials Science and Nanotechnology, and UNAM-National employed as both color converters typically on epitaxi- Nanotechnology Research Center, Bilkent, Ankara Turkey 06800 ally grown LEDs and as emissive layers of electrolumines- and Luminous! Center of Excellence for Semiconductor Lighting and cent devices. In the LEDs employing colloidal nanopar- Displays, School of Electrical and Electronic Engineering, School of ticles as color converters, the color-conversion layer is, Physical and Mathematical Sciences, School of Materials Science in general, prepared by blending the colloidal material and Engineering, Nanyang Technological University, Singapore within a polymeric encapsulation matrix and placed on 639798, E-mail: [email protected] © 2016 Talha Erdem and Hilmi Volkan Demir, published by De Gruyter Open. This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivs 3.0 License. Unauthenticated Download Date | 6/12/16 12:09 AM Colloidal nanocrystals for quality lighting and displays Ë 75 top of a near-ultraviolet (near-UV) or blue-emitting LED colloids can be developed. However, in contrast to LEDs chip that subsequently excites the colloidal semiconduc- and displays, the problems that need to be overcome to tors in the film. In the electroluminescent devices, the realize colloidal lasers are more serious. Since the lasers colloidal materials were usually sandwiched between lay- operate in the nonlinear regime in which the population ers of hole injection and transport, and layers of electron inversion of electrons and holes is required, suppression injection and transport. Electroluminescence is obtained of all the loss mechanisms including Auger recombination through the radiative recombination of injected electrons and surface traps and increasing the stability of the emit- and holes within the colloidal semiconductor material. A ters are of significant importance [17]. Therefore, develop- major advantage of using colloidal materials in both color- ing lasers involving colloidal emitters takes more effort but converting and electroluminescent LEDs comes from their it is also an open field for further improvements. To date, narrow-band emission spectra allowing for quality white- no electrically driven laser of colloidal materials could be light-emitting devices. As a result, high color rendition per- presented; however, a wide variety of lasers with optical formance along with high photometric efficiency can be excitation have already been reported for QDs, nanorods, realized at the same time [12]. In addition, due to the ris- NPLs, and perovskites. ing concerns regarding the supply of rare-earth ion based phosphors [13], colloidal semiconductor materials have stepped forward in recent years [14] since they can be syn- 2 Color-converting colloidal thesized from abundant materials having supply chains more immune to political tensions. materials for lighting Similar to lighting, colloidal materials have been in- vestigated in displays as color converters and also as ac- High-quality lighting requires the optimization of various tive electroluminescence layers. Their use in displays for performance metrics including the ability to render the lighting inherits significant similarities; however, the use real colors of the objects along with a strong overlap of of colloidal materials in displays poses additional advan- the emission spectrum with the eye sensitivity function tages. First of all, purer colors (in other words, more sat- and a warm white shade [15]. The color rendition capa- urated colors in color science terms) can be realized as a bility of the light sources is, in general, evaluated using result of significantly narrow band edge emission of the color rendering index (CRI). The worst color rendition per- colloidal materials. These pure colors obtained from col- formance is quantified with −100 while the perfect per- loids increase the range of colors that can be defined by formance is 100. In addition to the color rendition per- the display [15], which is also known as the color gamut. formance of the light source, it is also important to max- When these materials are utilized as color converters, they imize the fraction of the light produced by the light source are in general integrated on a blue LED chip as in the case that can be perceived by the human eye. Even if the emit- of lighting applications or as a remote color converter in ter is quantum mechanically very efficient, it might not a glass tube on the periphery of the optical back plane have any meaning as a light source for general lighting ap- or in a plastic film on the back plane of the display away plications in the case that the optical power is wasted in from LEDs. The generated light then passes through polar- the spectral regime where the human eye is not sensitive. izers, color filters, and liquid crystals to obtain the desired Therefore, overlap of the emission spectrum with the hu- color controlled at individual pixel level [16]. The use of man eye sensitivity function is very crucial for efficient il- the colloidal materials as active emissive layers in electro- lumination. This overlap is quantified using luminous ef- luminescent devices, on the other hand, requires pixelated ficiency (LE) of the optical radiation (LER), which takes formation of the LEDs. In these displays, there is no need values >350 lm/Wopt for high-efficiency light sources. The to use color filters or polarizers, which block a significant electrical efficiency of the light source is also an important amount of light leading to decreased efficiencies and heat- parameter for the performance of a light source. This met- ing, if single colored LEDs controlled at individual pixel ric is typically evaluated using the
Recommended publications
  • Environmentally Friendly Quantum Dots for Display Applications
    Environmentally Friendly Quantum Dots for Display Applications E. Jang SAIT, Samsung Electronics, Suwon, Korea, email: [email protected] Abstract— Ever since the physics of quantum dot (QD) was Color IQ technology, which was the glass tube optic using Cd- discovered, much research effort has been carried out for based QD. After that, TCL, Philips, BOE, Hisense and Konka more than 30 years, and lots of applications adopting QDs applied the same technology for their TV and monitor have been proposed. Especially, wide color gamut displays products. Nanosys has been very active in commercializing using QDs as active light emitting materials have drawn QD-film through the joint development with film-fabricating much attention. And, the QD-based consumer displays such companies such as 3M, LMS, Hitachi, and Nitto Denko. as LED TVs, tablets, and special monitors are now on the Starting from Amazon’s Kindle fire tablet, QD color market. They provide best color gamut, reasonable power converting film, which is called as QDEF, was adopted in the ASUS’s laptop and monitor, and TVs of Hisense, TCL, Vizio, efficiency, and affordable price showing superior competitive AUO. In China, Najing technology started to provide QDs to edge to OLED technology. However, still there are issues film makers such as Sangbo and Poly-OE, and work with TCL and argues using Cadmium containing materials in practical and Hisense to produce TVs. Nanoco is one of the pioneer consumer devices. In spite of the European RoHS companies to have developed the Cd-free QDs from the Exemptions, we need to be aware the environmental risk of beginning, and they have collaborated with Dow chemical and producing large quantity of Cd-containing materials and Merck for the mass-production.
    [Show full text]
  • Recent Advances on Quantum-Dot-Enhanced Liquid-Crystal Displays Haiwei Chen, Juan He, and Shin-Tson Wu, Fellow, IEEE
    IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS, VOL. 23, NO. 5, SEPTEMBER/OCTOBER 2017 1900611 Recent Advances on Quantum-Dot-Enhanced Liquid-Crystal Displays Haiwei Chen, Juan He, and Shin-Tson Wu, Fellow, IEEE (Invited Paper) Abstract—We review recent advances in quantum dot (QD)- en- high efficiency, and low cost [17]–[20]. However, the narrowest hanced liquid crystal displays (LCDs), including material formu- full width at half maximum (FWHM) of the green phosphor lation, device configuration, and system integration. For the LCD (β-sialon:Eu2+ ) is still as broad as 55 nm [20]–[22]. While system, we first compare the color gamut difference between the 4+ commonly used Gaussian fitting method and that using real emis- for red phosphor (K2 SiF6:Mn ) with five emission peaks, its sion spectra. Next, we investigate the Helmholtz–Kohlrausch effect. individual FWHM is indeed quite narrow, but the average peak Our simulation results indicate that QD-enhanced LCD appears wavelength centers at ∼625 nm, which is not deep enough 1.26X more efficient than organic light-emitting diode (OLED) dis- [23]–[25]. As a result, the RGB lights still show a relatively large play due to its wider color gamut. Finally, two new trends for QD- overlap after passing through the color filters. These crosstalks LCDs are discussed: 1) replacing conventional color filters with a QD array, and 2) emerging quantum rod (QR)-enhanced backlight. greatly reduce the color gamut. Their inherent advantages, technical challenges, and potential so- Recently, quantum dot (QD)-enhanced backlight is emerging lutions are presented. We believe the prime time for QD-enhanced and it has found widespread applications because of following LCDs is around the corner.
    [Show full text]
  • Information Display Magazine Vol. 33 No. 2, March/April 2017
    Mar-Apr Cover_SID Cover 3/4/2017 10:05 AM Page 1 DISPLAY WEEK 2017 PREVIEW AND DISPLAY MATERIALS March/April 2017 Official Publication of the Society for Information Display • www.informationdisplay.org Vol. 33, No. 2 RADIANT FROM EVERY ANGLE LEADER IN DISPLAY TEST SYSTEMS Any way you look at it, your customers expect a fl awless visual A Konica Minolta Company experience from their display device. Radiant Vision Systems automated visual inspection solutions help display makers ensure perfect quality, using innovative CCD-based imaging Visit us at solutions to evaluate uniformity, chromaticity, mura, and Booth #1129 defects in today’s advanced display technologies – so every Display Week 2017 smartphone, wearable, and VR headset delivers a Radiant experience from every angle. May 23-25 | Los Angeles, CA Radiant Vision Systems, LLC Global Headquarters - Redmond, WA USA | +1 425 844-0152 | www.RadiantVisionSystems.com | [email protected] ID TOC Issue2 p1_Layout 1 3/6/2017 4:10 PM Page 1 Information SOCIETY FOR INFORMATION DISPLAY SID MARCH/APRIL 2017 VOL. 33, NO. 2 ON THE COVER: The winners of this year’s DISPLAY major awards from SID are: (clockwise from top left) DISPLAYShui-Chih WEEK 2017 PREVIEW Alan AND Lien DISPLAY, MATERIALSKenneth I. Werner, Martin S. Banks, Deng-Ke Yang, Yi-Pai Huang, and Hiroyuki Ohshima. March/April 2017 Official Publication of the Society for Information Display • www.informationdisplay.org Vol. 33, No. 2 contents 2 Editorial: Onward to Display Week n By Stephen P. Atwood 3 Industry News n By Jenny Donelan 4 Guest Editorial: Advances in Materials for Display Applications n By Ion Bita 6 Frontline Technology: Emerging Solution-Processable Luminescent Nanomaterials in Hybrid Structures Offer New Solutions for Displays and Lighting As the development of quantum dot and perovskite luminescent materials accelerates, it is Cover Design: Acapella Studios, Inc.
    [Show full text]
  • “LCD TV Matters” Volume 6, Issue 1
    “LCD TV Matters” Volume 6, Issue 1 "A Great TV in Every Room" LCD TV Association LCD TV Matters November 2019 Contents Chairman’s Corner: Is 2019 the year of the Quantum Dot TV? Bruce Berkoff 3 LCD TV News compiled by Veritas et Visus 6 Sharp to re-enter U.S. TV business SHARP showcases world’s largest 8K LC Display 5G and UHD 8K – a developing symbiosis – reports FCC Samsung Display formally announces its $10.8 billion investment in QD-OLED TV production Sharp unveils new 80-inch 8K LCD ABI: 4K TV thriving, but 8K will gain ground 2018 TV shipments saw decade’s best growth says Futuresource Consulting GfK: TV has biggest impact on consumer purchasing FCC proposes to boost DBS regulatory fee again Over 233 million 4K TVs to ship in 2024, with 8K on the horizon Hisense shows off 5K, 21:9 display Samsung predicts fast 8K TV adoption driven by 5G networks IHS Markit: TCL surges to the top of the North American TV market TV makers to cut display panel demand, IHS Markit says Number of cord cutting homes nearing number of pay-TV subscribers in US, reports eMarketer Hulu says 70% of its 82 million viewers are on ad-supported plan ATSC 3.0 to be deployed in 40 U.S. markets by end of 2020 Leichtman: Pay-TV bloodletting continues Roku and Amazon now control nearly 70% of US streaming media player market 7 video trends that will dominate in 2019 and beyond, infographic from Branex Global HDMI Cable Market 2019-2023| Growing Popularity of HDMI 2.1| Technavio Pay-TV lost 1.5 million subscribers in Q2 2019, says Leichtman Marion Stokes recorded 30+
    [Show full text]
  • Nanoco Group Initiation of Coverage
    Nanoco Group Initiation of coverage Quantum leap Tech hardware & equipment 11 May 2017 We believe that factors are finally aligning to support adoption of Nanoco’s quantum dots in the 250m+ unit per year TV and computer display Price 32.25p markets. With a large addressable market and an operationally geared Market cap £77m model, it does not take aggressive assumptions for earnings to scale and the rating to look very inexpensive. We believe a substantial re-rating Net cash (£m) at 31 January 2017 8.3 upwards would be justified as support for our estimates builds. Shares in issue 238.2m Free float 85% Year Revenue PBT* EPS* DPS EV/sales P/E end (£m) (£m) (p) (p) (x) (x) Code NANO 07/16 0.5 (12.3) (5.2) 0.0 131.5 N/A 07/17e 1.6 (10.2) (4.3) 0.0 38.4 N/A Primary exchange LSE 07/18e 16.3 0.8 0.3 0.0 3.8 96.4 Secondary exchange N/A 07/19e 32.2 12.4 4.9 0.0 1.9 6.6 Note: *PBT and EPS are normalised and diluted, excluding intangible amortisation, Share price performance exceptional items and share-based payments. Quantum dot uptake cycle in display to hit its stride Quantum dots (QDs) significantly enhance the colour range of LCD displays, enabling a picture quality competitive with the rival OLED technology with better energy efficiency. Implementing the technology requires little disruption to the established LCD TV supply chain and therefore the cost is substantially lower than OLED.
    [Show full text]
  • Review of Impact of Potential New Rohs Substance Restrictions for Indium-Phosphide
    Review of impact of potential new RoHS substance restrictions for Indium-Phosphide Abstract Nanosys analysis of InP Quantum Dot usage in the EU for the period from 2018 – 2028. Includes market analysis for EU display market and Quantum Dot component designs. November 2019 Review of impact of potential new RoHS substance restrictions for Indium-Phosphide TABLE OF CONTENTS SECTION 1 – INP QUANTUM DOTS AND THE DISPLAY MARKET .................................................. 2 Display Industry Economics .............................................................................................................................. 2 Estimated Volumes of InP in Display Applications in the EU, 2018 – 2028 ........................................................... 3 Overview of Quantum Dot Configurations for Displays, 2018 – 2028 .................................................................. 4 “On-Edge” and “On-Chip” Configurations ................................................................................................................ 4 Quantum Dot Enhancement Film (QDEF) ................................................................................................................. 5 Quantum Dot OLED (QD-OLED)................................................................................................................................. 6 Quantum Dot Electro Luminescent (QDEL) ............................................................................................................... 8 Amount of InP Required Per Display ................................................................................................................
    [Show full text]