Enhancing Optical Performance for White Light-Emitting Diodes Using Quantum-Dots/Boron Nitride Hybrid Reflective Structure

Quantum dots (QDs) are usually used with phosphor to obtain white light-emitting diodes (WLEDs) due to their excellent lighting characteristics. For lighting effect improvement, the QDs layer and the phosphor layer are supposed to be separated to reduce reabsorption loss and enhance QDs stability. Based on the separated structure, a QDs/boron nitride hybrid reflective (QBHR) structure is proposed to enhance the optical performance of WLEDs in this study. QDs were electrostatically bonded on the boron nitride (BN) pellets and their composite particles were subsequently mixed with silicone for LED encapsulation by a spinning-coated process. It could be easily managed the performance of QBHR structure by controlling the composite particles' concentration or centrifugal speed. The diffuse reflectance and photoluminescence (PL) intensity of QBHR structure with various thicknesses were analyzed. While applying with remote phosphor layer for WLEDs, the luminous efficacy of devices with QBHR structure increases with phosphor concentration, which are larger than that of QD/polydimethylsiloxane (QP) structures. It may be caused by the light extraction ability of the scattering BN particles and high color conversion efficiency (CCE) of QBHR structure. Finally, under the same correlated color temperature (CCT) of 3640 K, the luminous efficacy and CCE enhance by 14.2% and 19.5% using the QBHR structure, respectively. In addition, the QBHR structure shows better stability than the QP structure after aging for 387.75 h. In brief, the QBHR structure shows an effective and practical packaging method to produce high-performance WLEDs.