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Tuneable white-emitting LED needs no phosphor Researchers in Saudi Arabia have demonstrated white light emission from a phosphor-less LED. Generally, ‘white’ LEDs have a blue-emitting die topped with phosphors that convert some of that blue to broad-spectrum amber – which combined with the residual blue is seen by humans as cool white. Adding a red-emitting phosphor in the mix produces warm white LEDs. Daisuke Iida, Kazuhiro Ohkawa, and their team at King Abdullah University of Science and Technology (KAUST) have created at phosphor-free monolithic white-light LEDs using indium gallium nitride – the same combination normally used for blue LEDs. The emission wavelength of InGaN depends on the relative content of the indium and gallium: Gallium nitride emits ultraviolet light, while adding indium shifts emission to longer wavelengths through the visible spectrum. However, for a number of reasons, pushing emission as far as red by adding a lot of indium is problematic.

Kazuhiro ohkawaDaisuke iidaKing abdullah university of scienceKing abdullah universityApplied physics lettersகிங் அப்துல்லா பல்கலைக்கழகம் ஆஃப் அறிவியல்கிங் அப்துல்லா பல்கலைக்கழகம்பயன்படுத்தப்பட்டது இயற்பியல் எழுத்துக்கள்