Technology News - Light Generation

LEDs and OLEDs

Technology | OLEDs | White Paper | Jan 15, 2015

Holst Centre and Flex-o-Fab Take the First Step Towards "Lighting by the Mile"

Manufacturing flexible OLEDs using a R2R-process is crucial for reducing costs for coming down to an affordable price Researchers from the EU-funded Flex-o-Fab project have successfully fabricated working OLED devices on a flexible barrier layer produced in a roll-to-roll (R2R) process. Produced on a PET plastic film, this breakthrough is a significant first step towards taking flexible OLEDs ‘from lab to fab’ and hence to commercial production. It draws on technical developments achieved within both Flex-o-Fab and Holst Centre’s joint research program into high-performance flexible barriers for organic ... Read more »

Technology | Light Perception | White Paper | Jan 15, 2015

Ending the Invisible Threat - Confronting the LED Flickering Issue

Figure 5: The flicker comparison of lighting products (Sources: Michael Poplawski and Naomi Miller, ”SSL Flicker Fundamentals and Why We Care” - U.S Department of Energy, 2014) One of the topics in 2014 International LIGHTFAIR DOE training was “SSL Flicker Fundamentals and Why We Care“ (Michael Poplawski and Naomi Miller 2014),this reignited the industry’s discussion on light modulation. This topic was already raised by ASSIST earlier, where research on human’s level of tolerance to high-frequency flickers have been done and published in several lighting magazines by Rebekah Mullaney, hoping to encourage LED manufacturers and distributors to put more emphasis on ... Read more »

White Paper | Technology | Binning | Jan 09, 2015

LpS 2014 Scientific Award Winner Article: New Binning Strategy for White LEDs

Figure 1: Semantic contours for chromaticity differences from the chromaticity center in the CIE x,y chromaticity diagram for a warm white chromaticity center, the Planckian radiator at 2500 K; x=0.4770; y=0.4137 (light green dot). Going off the center in any direction, contours indicate “good-very good” (green contour), “good” (yellow contour), “moderate-good” (orange contour), “low” (red contour) and “bad” (lilac contour) perceived color agreement with the center. Contours of constant chromaticity differences (Δu’v’=0.001 - Δu’v’=0.007 i.e. approximations of MacAdam ellipses) measured from the chromaticity center are also shown After having recognized the deficiencies of the ANSI binning strategy, which is based on the visually false magnification of MacAdam’s ellipses, Dr. Peter Bodrogi and Prof. Tran Quoc Khanh from the Technical University Darmstadt propose a new binning strategy based on a so-called semantic interpretation to describe and easily communicate the magnitude of acceptable chromaticity differences. Read more »

Technology | Light Generation | White Paper | Jan 09, 2015

Compute Simulation Sheds Light On Why Blue LEDs Are So Tricky To Make

New research from academics from the University of Bath Department of Chemistry has uncovered the mystery of why blue light-emitting diodes (LEDs) are so difficult to make: (1) Calculated spin density resulting from (a) a Mg0Ga-associated hole localized on a neighboring N in the basal plane, (b) a Mg0Ga-associated hole localized on a neighboring axial N, and (c) a N vacancy. Light gray (green) [darker gray (blue)] spheres represent Ga (N) atoms. The darkest gray sphere represents a Mg atom in (a) and (b) (purple) and a vacancy in (c) (orange). Spin densities are indicated by (red) isosurfaces of density (au) 0.05, 0.025, and 0.01 for (a) and (b) and 0.01, 0.005, 0.0025 for (c). (2) Formation energy of VN (black line) and MgGa [light gray (red) line] as a function of Fermi energy above the VBM. Anion-rich conditions are assumed. The position of the conduction band minimum (CBM) is indicated by the broken line. For each value of Fermi energy, only the most stable defect charge state is shown, with a change in slope indicating a change in charge state Researchers in our Department of Chemistry have collaborated with groups at University College London (UCL) and Daresbury to uncover the mystery of why blue light-emitting diodes (LEDs) are so difficult to make, by revealing the complex properties of their main component – gallium nitride – using sophisticated computer simulations. Read more »

Technology | Light Generation | White Paper | Nov 21, 2014

Thermoresponsive PDLC Coating for Smart CCT-Tunable LED Applications

Thermoresponsive scattering coating for smart CCT-changing white LEDs: a) basic working mechanism; b) demonstrator using coated (bottom) and uncoated (top) warm white LEDs operating at a low current (~20 mA/LED - top picture) and at a high current (~80 mA/LED - the bottom); c) associated CCT vs. current diagram When the 2014 Nobel Prize in physics was awarded this October to three Japanese-born scientists for the invention of blue light emitting diodes (LEDs), the prize committee declared LED lamps would light the 21st century. Now researchers from the Netherlands propose a novel way to ensure the lights of the future not only are energy efficient but also emit a cozy warmth. Cornelissen and his colleagues from the Eindhoven University of Technology, Netherlands describe their new LEDs in a paper ... Read more »

Technology | Light Generation | Nov 06, 2014

Osram Reports Record Figures for Green InGaN-Based and Conversion LEDs

LEDs show a significant efficacy drop in the green spectral range – an effect known as the “green gap” phenomenon The “Hi-Q-LED” project funded by Germany’s Federal Ministry of Education and Research (BMBF) has made pioneering advances with green LEDs, greatly diminishing what is known as the “green gap” phenomenon – the significant drop in efficacy in the green spectral range. The result is a green-emitting LED based on indium gallium nitride (InGaN) semiconductors which achieves a record efficacy of 147 lumens per watt (lm/W) at a wavelength of 530 nanometers (nm) and a spectral width of 35 nm. In ... Read more »

Technology | OLEDs | Nov 03, 2014

Light in New Shape - BMBF-Funded Joint Project R2D2

The reserach progresses of the last five years have proven the technical feasibility of transparent light sources with very low energy consumption, which furthermore can be applied to flexible and pliable substrates The research progresses of the last five years have proven the technical feasibility of the vision of a transparent and flexible light sources with very low energy consumption in the form of first demonstrators. Now the BMBF-funded joint project R2D2 will start in November 2014 aiming at the investigation of production-related processes and technologies for the manufacturing of flexible OLED. Read more »

Technology | Light Generation | Oct 07, 2014

And the Nobel Price 2014 Goes To ... The Inventors of the Blue LED

The blue LEDs, invented by the winners, are the basis for today's white LEDs like - following the latest trend - these chip-LEDs The Royal Swedish Academy of Sciences has decided to award the Nobel Prize in Physics for 2014 to Isamu Akasaki from the Meijo University, Nagoya, Japan and Nagoya University, Japan, to Hiroshi Amano from the Nagoya University, Japan and to Shuji Nakamura from the University of California, Santa Barbara, CA, USA for the invention of efficient blue light-emitting diodes which has enabled bright and energy-saving white light sources. Read more »

Technology | Light Generation | Sep 25, 2014

Nanotechnology May Lead to Better, Cheaper LEDs

(a) Princeton researchers have used their expertise in nanotechnology to develop an economical new system that markedly increases the brightness, efficiency and clarity of LEDs, which are widely used in smartphones and other electronics. The illustration demonstrates how a conventional LED's structure traps most of the light generated inside the device; the new system, called PlaCSH, guides the light out of the LED. (lllustration courtesy of Stephen Chou et al.) (b) PlaCSH has a layer of light-emitting material about 100 nanometers thick that is placed inside a cavity with one surface made of a thin metal film (shown at left.) The key part of the device is a metal mesh (center) with incredibly small dimensions: it is 15 nanometers thick; and each wire is about 20 nanometers in width and 200 nanometers apart from center to center. An image of the experimental LED is shown at right. (Images courtesy of Stephen Chou et al.) Princeton University researchers have developed a new method to increase the brightness, efficiency and clarity of LEDs, which are widely used on smartphones and portable electronics as well as becoming increasingly common in lighting. Using a new nanoscale structure, the researchers, led by electrical engineering professor Stephen Chou, increased the brightness and efficiency of LEDs made of organic materials (flexible carbon-based sheets) by 57 percent. The researchers also report their ... Read more »

Technology | Light Perception | Sep 18, 2014

LpR 44 Article: Discomfort Glare Perception of Non-Uniform Light Sources in an Office Setting

Test setup of the different regions and luminance patterns under test LED based luminaires with different luminance patterns and recently with increasingly non-uniform luminance patterns are becoming mainstream. This trend makes discomfort due to glare an important topic. Based on an office setting and the comparison of results from three different regions, L. M. Geerdinck, J. R. Van Gheluwe and M.C.J.M. Vissenberg from Philips Research have reviewed the currently used formulae to predict discomfort glare to ascertain if they are still valid. Read more »

Technology | OLEDs | Sep 17, 2014

Printing Process of Metal Contacts for Reliable Contacting of Flexible OLEDs and Other Devices

Fraunhofer FEP works on cost-effective system solutions for flexible devices and presents results at Plastic Electronics 2014 A significant growth is predicted for the market of flexible devices. The topic “Wearables”, namely intelligent, wearable systems with several useful and funny features is currently one of the major discussion topics. To enjoy more comfort, exceptional designs and higher functionality manufacturers and users ask for flexible electronic devices, like displays, lighting elements or circuit boards. Read more »

Technology | Light Generation | White Paper | Aug 28, 2014

Osram Opto Demonstrates "3D nano LEDs" for White Light and Sees Series Maturity in Coming Years

Osram researchers make a 3D nano LED for white light shine on the wafer using two tiny, energized needles.The needles are pressed onto the contact surfaces of the chips, and the distance between the contact points corresponds approximately to the thickness of three sheets of stacked writing paper By making use of nanotechnology, Osram hopes to produce significantly more LED chips with its existing production plant. Osram researchers have for the first time succeeded in manufacturing a so-called "3D nano LED" for white light. The productivity boost is possible due to the special surface characteristics of the LED chip – in contrast to today's standard models, this is not smooth but consists of many adjacent, microscopically small columns with a three-dimensional structure, thus ... Read more »

Technology | Light Generation | Jul 03, 2014

Significant Technical Progress - BluGlass Demonstrates Best Ever RPCVD (p-GaN) Light Output

Demonstration of light emission at 473nm, with full width half maximum of 22nm, from a RPCVD p-GaN layer grown on a MOCVD partial structure Australian Cleantech innovator, BluGlass Limited, has announced today that it has been successful in demonstrating the best ever p-GaN light output using its propriety technology, Remote Plasma Chemical Vapour Deposition (RPCVD) on an MOCVD partial LED structure. This result is greater than a 10 fold improvement in LED efficiency over the first p-GaN demonstration data published by the company in December 2012, when the same measuring methodology is applied. This has been achieved by making ... Read more »

Technology | Light Generation | Apr 14, 2014

Developing Phosphor-Free White Light from Nanopyramid LEDs

Left: Fabrication schematic for phosphor-free nanopyramid LEDs by nanospherical-lens photolithography. Right: (a) Room-temperature photoluminescence spectra of nanopyramid LEDs with MQWs grown at different temperatures, along with reference structure grown on planar template. (b) Spectrum of ‘white LED’ (blue LED with yellow phosphors). (c) Electroluminescence spectrum of nanopyramid LEDs at 20mA; inset shows corresponding optical microphotograph Researchers in China have used nitride semiconductor nanopyramid structures to create light-emitting diodes (LEDs) with spectra that are similar to those provided by ‘white light’ LEDs with yellow phosphors [Kui Wu et al, J. Appl. Phys., vol115, p123101, 2014]. The researchers are at the Chinese Academy of Sciences’s institutes of Semiconductors and Mechanics, and Tsinghua University. A similar CAS/Tsinghua team previously reported such devices, using a polystyrene nanosphere mask to make holes ... Read more »

Technology | Light Generation | Mar 28, 2014

Osram To Demonstrate The World's Most Efficient LED Replacement Tube at Light+Building

Osram's record-breaking light source was developed by the central research department together with the optical semiconductor and lamp business units An Osram research team has succeeded in constructing the most efficient LED lamp in the world. The lamp in tubular form consumes only half the power of currently common fluorescent and LED tubes, and also achieves significantly superior colour rendering. Read more »

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