Reactive carbon dots/polysiloxane composites cross-linked silicone resin adhesives for stable white LED constructing

Abstract

Current high-performance commercial white LEDs typically rely on Ce:Y3Al5O12 (Ce:YAG) phosphors and their dispersed encapsulating material. However, Ce:YAG often has large particle sizes and does not react with the encapsulating material, causing stratification and sedimentation. To address this problem, a novel reactive carbon dots/polysiloxane (R-CDs/PS) composite was synthesized through a one-step solvothermal process involving citric acid, urea, 3-aminopropyltriethoxysilane (APTES), and vinyltrimethoxysilane (VTMS). The composite exhibits yellow emission at 528 nm under UV excitation and has a particle size of approximately 150 nm. To improve integration, vinyl adhesive (vinyl AD) and vinyl MDQ resin were designed and synthesized to enhance adhesion and mechanical strength. When dispersed in silicone resin adhesives (SRAs), R-CDs/PS composite forms a stable color conversion layer, avoiding stratification due to its nanoscale size and chemical cross-linking with SRAs. White LEDs can be easily produced by casting R-CDs/PS composites and SRAs onto LED chips, followed by high-temperature curing. These LEDs exhibit desirable optical properties, including CIE coordinates of (0.33, 0.34), a CRI of 82.2, and a CCT of 5355 K, making them suitable for indoor lighting. This study not only introduces a practical approach for fabricating fluorescent and encapsulating materials but also offers a valuable strategy for improving the stability of white LEDs.