Effect of quartz lens structure on the optical performances of near-ultraviolet light-emitting diodes

Near-ultraviolet light-emitting diodes (NUV-LEDs) have been a rising UV light source for identification, resin curing, ink-printing, and illumination. In pursuit of more extensive application in different fields, their optical performances are obliged to be better. In this paper, we investigated the effect of a quartz lens structure on the optical performances of NUV-LEDs. The feature size of the quartz lens was optimized by optical simulations. When the quartz lens has the optimized feature size with a height above 1.8 mm while adding a silicone layer between the chip and the lens, the NUV-LEDs achieve the highest light efficiency, and exhibit a smallest light spot and largest light energy at the center region. Furthermore, different lenses were prepared and applied in the packaging of NUV-LEDs. As a consequence, the light output power of NUV-LEDs with a silicone layer is enhanced by 20.19% at the current of 220 mA. The light output power of NUV-LEDs is enhanced by 38.66%, 43.98%, and 53.30%, respectively, by using the different quartz lenses at the current of 220 mA, and the NUV-LED achieves the highest luminous intensity by 0.098 cd and smallest output light angle by 106.0°. It is attributed to the significant refraction effect of the quartz lens, which improves the optical performances of NUV-LEDs.