Internal quantum efficiency of UV μLED chips

Abstract

Micro light emitting diode (μLED) displays have been in development since 2017, aimed for application in 2020. However, when using three-color, i.e., red, blue, and green LEDs, or blue LEDs that excite red and green phosphors, many challenges arise in mass production, cost, and quality. Our group has devised an ultraviolet (UV)-excited red, green, and blue (RGB) display that excites red, green, and blue phosphors using UV-LEDs. This paper studies how the composition and crystal defects of a light-emitting layer affect the luminous efficiency of a UV μLED chip from the perspective of internal quantum efficiency (IQE). It was confirmed that the luminous efficiency improves by making the LED chips in the near ultraviolet range μ-size. The UV μLED chip emitting at 385 nm exhibited a more linear output than a 400-nm purple μLED chip.