Research on the different nanoparticle-based coatings to improve the optical performance of the ultraviolet light-emitting diodes

With the emphasis on the environment, the ultraviolet light-emitting diode (UVLED) has been a new hotspot of the LED development to replace the traditional polluted mercury lamps. However, the optical efficiency of UVLED is much lower than that of the blue commercial LED, which is necessary to be improved to satisfy the UVLED application. Herein, we introduce the nanoparticle-based coating covering the bracket for the UVLED. Different nanoparticles including AlN, TiO2, ZnO and ZrO2 are selected in this study. After applying the nanoparticle-based coating, the optical performances of these UVLEDs were compared. The optical output of the ZrO2-based UVLED has been improved greatly and the AlN-based UVLED only owns little advantage in radiant flux. Meanwhile, the ZnO and TiO2 based UVLED decrease the light output instead. Compared with the UVLED without nanoparticle-based layer, the optical output increase of ZrO2-based UVLED can be up to 9.0 % under 500 mA. This optical output improvement is attributed to the reflection effect of the nanoparticle-based coating on UV light (367 nm). So with the ZrO2-based coating for the UVLED, the UV reflection was increased and the optical performance is enhanced greatly. This strategy provides a new direction for UV packaging and it is beneficial to promote the process of UVLED applications.