A new way of making white LEDs without phosphor has been published by a research team at the University of California at Santa Barbara; Nobel laureate and blue/white LED pioneer Shuji Nakamura is a co-author.
White LEDs are usually made of blue LEDs with a yellow phosphor; the admixed light (blue from the chip and yellow from the phosphor) is white. But phosphor-converted white LEDs usually suffer energy loss and reduced thermal stability. Phosphor-free LEDs, on the other hand, have been hard to make. The UCSB team’s innovation is an easier new method to achieve efficient and polarised white LEDs grown directly on a GaN substrate.
The team adopted a top blue QW (quantum well) and a bottom yellow QW on semipolar bulk GaN substrate to produce phosphor-free white InGaN LEDs with a peak wavelength of 427 nm in blue and 560 nm in yellow and an output power of 0.9mW.
The researchers believe the phosphor-free LEDs with advanced efficiency could be promising as backlight sources and offer possibility for µLEDs used in visible light communication.