Improving Optical Performance of NUV-LEDs by Highly Reflective BN/Silicone Structures

Near-ultraviolet light-emitting diodes (NUV-LEDs) are more likely to be commercially fabricated. The improvement of their wall-plug efficiency (WPE) by facial and effective methods has made a great impact. We propose a highly reflective boron nitride silicone (BN/silicone) layer to improve the light output power for NUV-LEDs. Our results show that increasing the BN concentration contributes to a higher UV-reflectivity of the BN/silicone layers. When the BN concentration increases from 0.5 to 15 wt%, the light output power enhancement increases gradually, thus achieving a maximum light output power enhancement of 46.2% for NUV-LEDs at a driving current of 350 mA compared with pure silicone encapsulation devices. This significant improvement is attributed to the increased UV-reflectance by the polymer-based lead-frame and packaging materials. Furthermore, the emission angle is decreased by 7.8° at a BN concentration of 15 wt% at 350 mA owing to the strong scattering ability of the BN/silicone layer. This provides more concentrated energy in lighting applications.