Strategic point defect engineering toward abnormal thermal quenching in Sm3+-doped Na-rich Na1.5La1.5TeO6 phosphors for LEDs applications

Thermal stability holds particular significance for phosphors intended for LEDs . Abnormal thermal quenching was successfully reached by strategic point defect engineering by inserting Frenkel defects and nonequivalent substitution defects in novel Sm 3+ ions doped Na-rich distorted double perovskite Na 1.5 La 1.5 TeO 6 phosphors. Its integral intensity at 420 K (115.03 %) was far higher than that of room temperature . Besides, the phosphors exhibited a pronounced orange-red emission peak at 644 nm when excited at 404 nm, which was ascribed to the 4 G 5/2 - 6 H 9/2 transition of Sm 3+ ions. The concentration quenching phenomenon resulting from dipole-dipole interactions was observed in the phosphors, and the optimal concentration of dopant Sm 3+ was determined to be 1 mol%. After calculation, it was surprising that the color purity values of all phosphors were not less than 99.9 %. Additionally, the internal quantum efficiency (IQE) reached 65.30 %, and the activation energy ( E a ) of Na 1.5 La 1.5 TeO 6 :1 mol%Sm 3+ was 0.570 eV. Meanwhile, the emission spectrum of the produced orange-red light emitting diodes (LEDs) exhibited a close correspondence with the absorption curves of various plant pigments (chlorophyll b , allophycocyanin, phycocyanin, phytochrome red and far red (P R and P FR )). The prepared white light emitting diodes (WLEDs) possessed low correlated color temperature (CCT) of 4769 K and as high general color rendering index (CRI, R a ) value as 91. In summary, the phosphors presented promising options for plant-cultivating LEDs and high CRI WLEDs based on their superior optical and thermal properties .