Germans see white light at the end of the tunnel Steve Bush
The Fraunhofer Institute in Freiburg, Germany, has developed a white LED which does not use three different coloured LED chips in the same package.
Instead, it uses a single chip and fluorescent material. The material absorbs some light at the wavelength emitted by the chip, and re-radiates the energy at other wavelengths, filling out the optical spectrum and appearing white.
Fluorescent materials emit at longer wavelengths than they absorb at, so the chip has to emit the highest wavelength (blue) needed. Juergen Schneider, a spokesman for the project, said: "The need for a blue LED chip limits the overall efficiency of the white LED because blue LEDs are not the best at converting electricity into light. It's still around four times better than an incandescent lamp. But the main advantage is that lifetime will be around 10 years."
Applications will be as indicators initially. Schneider said: "It will be quite a while before we light our living rooms with them."
The LEDs use GaN on either a sapphire or SiC substrate (bulk, mono-crystalline GaN does not exist). The device, under the name LUCOLED, will be marketed by Siemens.