Bright red phosphor is based on silicon quantum dots

A group at the University of Washington (Seattle, WA) has demonstrated phosphors based on silicon (Si) quantum dots (QDs) that are efficient emitters (with an external quantum efficiency up to 15.9%), can be made to have a peak wavelength that falls anywhere from the near-IR to the green, and can be fabricated cheaply. The phosphors, which are stable at room temperature due to an oxide passivating shell, are nontoxic—unlike otherwise useful conventional QD phosphors based on II-VI semiconductors like cadmium selenide, cadmium zinc selenide, or cadmium zinc sulfide.

Scanning electron micrograph of silicon quantum dots, which form a red-emitting phosphor useful in white LEDs

Electrochemical etching of a Si wafer produces Si microparticles with attached QDs; these particles are dispersed in ethanol and can be made to react with alkoxysilanes to form a suspension in nonpolar solvents for further processing. The red-emitting version of the phosphor has a broadband excitation band with a 70% excitation efficiency between 345 and 475 nm—a good match for blue- and violet-emitting gallium nitride-based LEDs (the figure shows excitation at 365 nm). The red phosphor in solvent can be formed into thin films by drop-casting or spin-coating. Scanning-electron micrographs of the films show micron- and submicron-sized clusters. Such red phosphors are needed to improve the color rendition of white LEDs. Contact Chang-Ching Tu at tucc@u.washington.edu.

50 YEARS OF SOLID-STATE LASERS


A long way from the ruby laser

Most Popular Articles

Webcasts

Ray Optics Simulations with COMSOL Multiphysics

The Ray Optics Module can be used to simulate electromagnetic wave propagation when the wavelength is much smaller than the smallest geometric entity in the ...

Multichannel Spectroscopy: Technology and Applications

This webcast, sponsored by Hamamatsu, highlights some of the photonic technology used in spectroscopy, and the resulting applications.

Handheld Spectrometers

Spectroscopy is a powerful and versatile tool that traditionally often required a large and bulky instrument. The combination of compact optics and modern pa...

Fracking, climate change, and lasers:  new tools to reduce fugitive methane emissions

This webcast, sponsored by Hamamatsu Corporation, covers recent developments and field deployments of compact quantum-cascade-laser (QCL)-based methane senso...
White Papers

Narrow-line fiber-coupled modules for DPAL pumping

A new series of fiber coupled diode laser modules optimized for DPAL pumping is presented, featur...

Accurate LED Source Modeling Using TracePro

Modern optical modeling programs allow product design engineers to create, analyze, and optimize ...

Optical Isolators Improve Engraving Performance of Pulsed Fiber Lasers

The deleterious effects of back reflections on pulsed fiber lasers used in marking and engraving ...
Technical Digests

ADHESIVES, SEALANTS, AND COATINGS: Solutions for optical technologies

A vast array of optical systems of various types and degrees of complexity require the use of adh...

WAVELENGTH-SWEPT LASERS: Dispersion-tuned fiber laser sweeps over a 140 nm range for OCT

By eliminating the use of mechanical tunable filters and instead tuning by intensity-modulation i...

Keeping pace with developments in photonic materials research

For demanding or custom spectroscopy solutions, care must be taken in selecting and integrating a...

HIGH-POWER FIBER LASERS: Working in the kilowatt regime

High-power materials-processing fiber lasers are available in an increasing variety of forms, as ...

Click here to have your products listed in the Laser Focus World Buyers Guide.
Social Activity
  •  
  •  
  •  
  •  
  •  
Copyright © 2007-2014. PennWell Corporation, Tulsa, OK. All Rights Reserved.PRIVACY POLICY | TERMS AND CONDITIONS