A Remarkable Color Rendering Index of 87 in White Laser Lighting Diode Enabled by Amide‐Functionalized Carbon Dots Phosphor with High Photothermal Stability

AbstractCarbon dots (CDs) phosphors in white laser diodes (WLD) have the advantages of sufficient surface functionalization sites and low cost. Specially, their color rendering index (CRI) in WLD is unsatisfactory due to the uncontrollable synthesis process and low thermal stability. Herein, surface nitrogen‐containing groups of CDs are synthesized from phenylenediamine isomers and trimeric acid, and the optical and thermal properties of CDs are modulated by introducing amide bonds (–CONH). By varying the phenylenediamine isomers, CDs synthesized from o‐phenylenediamine, m‐phenylenediamine, and p‐phenylenediamine emit different fluorescence peaks at 534, 498, and 434 nm, respectively. Further investigation shows that the increase of –CONH and adjacent –NH2 favors the reduction of bandgap, which in turn induces redshifted emission. The green‐emitting CDs are also found to be thermally stable at high –CONH contents up to 10.35%. Finally, by assembling the fluorescent film with 450 nm laser diode, WLD with color coordinates of (0.3767, 0.3540), correlated color temperature of 3924 K, and CRI of 87 is realized, and its CRI reaches the advancing value for single phosphors‐based WLD devices. This work will lay the theoretical and experimental foundation for the realization of the low‐cost, high photothermal stability, high‐color‐rendering‐index CDs‐based laser lighting devices.