Robust and Reliable Organic Dye-Embedded Zinc Oxide Nanocomposite Phosphor with a Broad Spectrum and High Efficiency Enables an Eco-Friendly White Laser Light Diode

In pursuit of low carbon and environmental protection, zinc oxide (ZnO) nanoparticles (NPs) have great potential as light-converting phosphors in white-light laser illumination due to their exceptional optical properties, high thermal stability, and environmental friendliness. However, their short-wavelength emission and low photoluminescence quantum yield (PLQY) drawbacks limit their compatibility with white laser diodes (WLDs). Herein, rhodamine B (RhB)-containing ZnO nanocomposites (R-ZnO NPs) were designed and successfully synthesized, combining the advantages of ZnO NPs and the organic dye. Compared with the ZnO NPs, the emission spectrum of R-ZnO NPs was red-shifted to the yellow-orange region with the optimal emission peak at 578 nm, and the PLQY was significantly increased to 85.21%. The results indicate that the columinescence of ZnO and RhB in the R-ZnO NPs promotes the spectral red shift and broadens the luminescence range under blue laser excitation. The related reason may be that the RhB embedded by ZnO crystals restricts its molecular vibration and reduces the nonradiative energy dissipation, which improves its PLQY. Based on the high brightness, thermal stability, and long wavelength solid-state luminescence features of R-ZnO NPs, single matrix R-ZnO solid-state fluorescent thin films were constructed and assembled with 450 nm blue laser diodes. WLDs with Commission Internationale de L'Eclairage (CIE) color coordinates of (0.33, 0.33), a correlated color temperature of 5237 K, and a color rendering index (CRI) of 73 were finally obtained. This study provides a new strategy for realizing high-PLQY, long wavelength-emitting ZnO NPs and a theoretical and experimental basis for ZnO-based laser illumination devices.