Lighting is a major application of UV (ultraviolet) LED currently and 385nm (spectral wavelength) UV-A LED is competitive with mercury-vapor lamps in terms of performance-cost ratio while 365nm UV-A LED is expected to increase in power output by 84.8% and decrease in production cost by 71% during 2014-2016, according to Digitimes Research.
Prices for UV LED are in negative correlation with wavelength because the shorter the wavelength, the more difficult the production, Digitimes Research indicated. For example, prices for a 400nm UV LED chip and a 365nm one are twice and 30 times, respectively, that for a blue-light LED chip. In addition, UV LED entails much higher equipment cost. For example, cost for a MOCVD set used to produce 4-inch blue-light LED epitaxial wafers stands at US$940,000 and one for producing UV LED wafers costs US$2.6-3.2 million.
External quantum efficiency (an indicator of LED luminous effect) of UV LED drops along with decrease in wavelength, standing at 50% for 385nm UV-A LED, 30% for 365nm UV-A LED, 12% for 270-280nm UV-C LED and 3% for 250nm UV-C LED.
Although UV-C LED (200-275nm) has comparatively high production cost and low external quantum efficiency, it is in growing application to sterilization and medical purposes. Demand for UV-C LED will take off when yield rates in production rise to reduce prices to an acceptable level.
