Post-doping induced morphology evolution boosts Mn²⁺ luminescence in the Cs₂NaBiCl₆:Mn²⁺ phosphor

As we know, defects caused in the synthetic process of metal halide perovskite are the most difficult to overcome, and greatly limit their photoelectric performances. Herein, a post-doped strategy was utilized to achieve an interesting morphology evolution from a standard octahedron to a snowflake-like sheet during the Mn²⁺-doped Cs₂NaBiCl₆ process, which realizes the obvious photoluminescence quantum efficiency (PLQY) enhancement of the Cs₂NaBiCl₆:Mn²⁺ phosphor. This surprising evolution is ascribed to the morphology collapse and reconstruction induced by Mn²⁺ exchange. The obtained phosphor exhibits enhanced 31.56% PLQY, which is two-fold higher than that synthesized by the traditional co-precipitation method, with broad emission spectrum and good PL color stability at 150 °C. Combined with the Cs₂SnCl₆ : 1mol%Bi³⁺ phosphor to fabricate the phosphor-converted light-emitting diode, bright white light emission with Ra = 88, CCT = 4320 K, CIE (0.36, 0.33) and a good application potential in high-resolution PL imaging agents was obtained. This work provides a possible effective strategy to improve the PL performance for impurity-doped lead-free metal halide perovskite.