High quality white light emission from Sb3+, Tb3+ and Mn2+ co-doped Cs2NaScCl6 double perovskites†

Abstract

Recently, the splendid strategy of co-doping ns² electron configuration ions with rare-earth ions in all-inorganic lead-free halide double perovskites has been proposed to overcome the weak absorption cross-section of the f–f transition of rare-earth ions and achieve efficient white emission. But few of them can really provide effective red emission in lead-free halide double perovskites, despite the wide variety of rare-earth ions, and lead-free halide double perovskites with co-doping rare-earth ions and doping ns² electron configuration ions usually exhibit an unsatisfactory color rendering index due to the narrow characteristic emission peaks of rare-earth ions. To address this issue, Mn²⁺ ions with red wide peak emission were introduced into Cs₂NaScCl₆ simultaneously with Tb³⁺ ions and Sb³⁺ ions in this work. The white light emission was observed in Cs₂NaScCl₆:0.01Sb³⁺,0.12Tb³⁺,0.07Mn²⁺ under 336 nm excitation because the presence of energy transfer from Sb³⁺ ions to Mn²⁺ and Tb³⁺ ions enhances fluorescence performances of Mn²⁺ and Tb²⁺. The temperature-dependent spectrum of Cs₂NaScCl₆:0.01Sb³⁺,0.12Tb³⁺,0.07Mn²⁺ shows that it exhibits a stable white emission in the temperature range of 298–398 K, and it's emission intensity at 398 K only decreases by less than 18% of the initial intensity (at 298 K). Excitingly, WLED devices with a quite high color rendering index of 93.6, which is one of the best in lead-free halide double perovskites, and nearly standard white light CIE coordinates of (0.3425, 0.3435), have been fabricated by using Cs₂NaScCl₆:0.01Sb³⁺,0.12Tb³⁺,0.07Mn²⁺ and a 340 nm LED chip and can maintain a good white color stability at different working times and currents. These results indicate that Cs₂NaScCl₆:Sb³⁺,Tb³⁺,Mn²⁺ is an outstanding candidate for WLED applications.