Can white PV panels do the same as blue LEDs?

Developing and commercialising the blue LED led to the ongoing revolution in the lighting industry, something research facility CSEM wants to emulate with the development of a completely white solar panel.

Presenting at the 9th ENERGY FORUM conference on the building skins of the future (‘advanced building skins’), researcher Jordi Escarre Palou and his team from the Swiss Center for Electronics and Microtechnology (CSEM) showcased an all-white solar module with claimed efficiencies of over 10%.

Escarre Palou said in a statement: “We achieve the highest efficiency level through a combination of crystalline high-performance solar cells with a film treated using nanotechnology, which only filters a particular wavelength of light through to the cell and reflects the visible spectrum as a diffuse illumination.”

Read the full story: PV Tech

Training the Light to Cool the Material is Strikes

Light might one day be used to cool the materials through which it passes, instead of heating them, thanks to a breakthrough by engineers at Lehigh and Johns Hopkins Universities.

The discovery, says Yujie Ding, professor of electrical and computer engineering at Lehigh, could lead to smaller, lighter and cheaper communication devices with faster switching times, increased output and higher operating voltages.

Ding and Jacob B. Khurgin, professor of electrical and computer engineering at Johns Hopkins, have achieved the most favorable ratio to date between opposing types of light-scattering phenomena that occur in semiconducting materials.

They published their results recently in Laser and Photonics Review in an invited article titled “From anti-Stokes photoluminescence to resonant Raman scattering in GaN single crystals and GaN-based heterostructures.”

Photons—units of light energy—typically maintain the same kinetic energy and wavelength when they exit a material as they do when they strike it. Raman scattering, named for Sir Chandrasekhara Venkata Raman, the 1930 Nobel Prize winner in physics, refers to the small fraction of scattered photons whose kinetic energy and wavelength, or frequency, differ from those of incident photons.

Read the full story: LeHigh University

LG Chem Develops LED-level OLED Lighting Panel

LG Chem has succeeded in developing OLED lighting that has a light efficiency and duration almost equivalent to LED lighting. Therefore, the company announced that it will officially start to target the lighting market.

LG Chem announced on September 11 that the development of OLED lights with 100 lumens per watt was completed for the first time in the world, and products will begin to be sold in November. Light efficiency measures how much energy is transformed directly into light, as opposed to how much is lost to heat or inefficiency.

These new OLED lighting panels have the best light efficiency ever recorded (for OLEDs) of 100lm/W and can last more than 40,000 hours. LG Chem completely solved the weaknesses of existing OLED lighting, light efficiency, and duration. Now OLED lighting is competitive with fluorescent lights (100 lm/W, 20,000 hours) and LEDs (over 100lm/W, 50,000 hours).

The average efficiency of OLED lighting on the market now is around 60 lm/W. LG Chem has enhanced its technological leadership in the world’s OLED lighting market by developing an 80 lm/W product last year and, now, 100 lm/W.

Read the full story: Business Korea

Patterned substrates enhance LED light extraction

 

DONGGEUN KO, JACOB YOON, and JANGHO SEO describe how patterned wafers can help increase LED light extraction by reducing defect density and total internal reflection losses.

Manufacturers are quickly adopting nitride-semiconductor-based LEDs as a standard light source for a wide range of products from general lighting, automobile headlights, and traffic signals to backlighting for consumer devices like HDTVs, smartphones, and tablets, and displays large and small. Still, LED performance and cost are gating broad deployment of LED technology. Indeed, lower component pricing and greater light output could boost consumer market acceptance. LED chip manufacturers are looking to patterned sapphire-substrate manufacturing techniques to maximize light extraction and overcome obstacles to broader LED usage.

Patterns applied on an LED substrate or wafer can significantly increase the light output of LEDs in two ways. The technique can increase the light emission of active quantum well layers as the result of reduced epitaxial defect density. And patterned sapphire substrates can reduce light loss due to total internal reflection (TIR) phenomena by enabling a photon scattering effect.

Read the full story: LEDs Magazine

Experimental investigation of copper-grooved micro heat pipes (MHPs)

With the excellent thermal conductivity and the compatibility to micro electromechanical systems technology, silicon is widely used in micro heat pipes (MHPs). Copper shows higher heat transfer capability and capillary traction than silicon. Copper microgrooves were fabricated on the silicon wafer using electroforming technique in this paper. Water contact angle measurements and thermal behavior tests demonstrated that copper-grooved MHPs showed better performance than silicon ones. Under the input power of 5.99?W, the equivalent thermal conductivities of copper-grooved and silicon-grooved MHPs were 228.98?W/K???m and 196.26?W/K???m. This work showed the feasibility of copper grooved silicon based MHPs in heat transfer for high-power light emitting diode (HP LED).

Read the full story: The Journal of Solid State Lighting

Low-Cost and Colourful LEDs Made from Wonder Material Perovskite

Low-cost and colourful LEDs (Light-Emitting Diode) have been manufactured from a material known as ‘perovskite,’ potentially opening up a wide range of commercial applications.

Researchers from the University of Cambridge, University of Oxford and the Ludwig-Maximilians-University have demonstrated an application for perovskite materials to make high-brightness LEDs.

Perovskite

Perovskite is a group of materials having distinctive crystal structure of cuboid and diamond. Owing to their superconductivity and ferroelectric features, these can be used to convert light into electrical energy, according to a report by University of Cambridge.

This is the same perovskite that has been recently found to make efficient solar cells, which could replace silicon.

Read the full story: International Business Times

Toyoda Gosei and Harvatek Sign Silicate-based LEDs License Agreement

Harvatek Corporation (“Harvatek”) and Toyoda Gosei Co. Ltd (“TG”) have voluntarily signed and entered into a License Agreement relating to silicate-based LEDs.

TG, together with Tridonic Jennersdorf GmbH (Austria), Leuchtstoffwerk Breitungen GmbH(Germany), and Litec GbR (Germany) (together “B.O.S.E. Consortium”), owns basic patents relating to a technology for generation of white light using blue LEDs and novel yellow silicate phosphors. Silicate phosphors applied to blue LED chips enable manufacturing of packaged white LEDs with high-accuracy and high-brightness. Primary applications include cell phones, laptops,GPS and other small displays, accounting for high share of today’s global LED market.

Read the full story: LED Inside

Novel Glass Phosphors Outperform Silicone Phosphors for Next-generation Solid-state Lighting.

White light-emitting-diodes (WLEDs) perform well in many settings where solid-state light fittings with long lifetime, low power consumption, and high efficiency are required. However, high-power WLEDs suffer from high heat flux during operation. Improvements in chip structure and fabrication have solved the problem of heat degradation of chip materials, and now the challenge of high-power WLEDs is the reliability of their packaging.

The most common LED packaging material is silicone, a polymer-based material, which has cerium-doped yttrium aluminum garnet (Ce3+:YAG) phosphors blended into it to emit white light. These operate as color conversion elements, which transfer parts of the blue light emitted from a gallium nitride (GaN) LED chip to yellow light. Unfortunately, the extremely high heat flux radiated from the GaN chip induces bond breakage in silicone. The sub-band defects consequently make silicone yellowish and decrease transmittance of silicone. The optical performance of WLED modules such as lumen and chromaticity thus deteriorates after a period of operation. To address this, we have developed novel glass-based phosphors with high thermal stability.

Read the full story: SPIE

Novel Nanoparticle Production Method Could Lead to Better LED Lights, Lenses, Solar Cells

Sandia National Laboratories has come up with an inexpensive way to synthesize titanium-dioxide nanoparticles and is seeking partners who can demonstrate the process at industrial scale for everything from solar cells to light-emitting diodes (LEDs). Titanium-dioxide (TiO2) nanoparticles show great promise as fillers to tune the refractive index of anti-reflective coatings on signs and optical encapsulants for LEDs, solar cells and other optical devices. Optical encapsulants are coverings or coatings, usually made of silicone, that protect a device. Industry has largely shunned TiO2 nanoparticles because they’ve been difficult and expensive to make, and current methods produce particles that are too large. Sandia became interested in TiO2 for optical encapsulants because of its work on LED materials for solid-state lighting. Read the full story: LED Inside