A unique approach to significantly enhance the emission intensity of Cr³⁺ via reverse defect energy level control...

In recent years, Cr³⁺ doped near-infrared (NIR) phosphors have garnered significant scholarly interest due to their distinct properties and diverse applications. Nevertheless, the coexistence of Cr³⁺ and Cr⁴⁺ ions significantly impinges on luminous intensity and NIR efficiency. Here, for the first time, we propose a reverse defect energy level control method to enhance the emission intensity of Cr³⁺ by blocking the energy transfer pathway from Cr³⁺ to Cr⁴⁺. By doping Sr²⁺ ions in Ba₉Sc₂Si₆O₂₄:Cr³⁺/Cr⁴⁺, the luminescence intensity increased by 10 times, and the quantum efficiency rose from 2.9% to 25.6%. The full width at half maximum (FWHM) simultaneously decreased from 461 nm to 180 nm, setting a record. The defect energy level control method of inhibiting energy transfer could be conclusively demonstrated through luminescence kinetics testing, TL spectrum analysis, and associated theoretical calculations. Through precise defect regulation, the energy transfer efficiency between Cr³⁺ and Cr⁴⁺ decreased from 76.85% to 0%. The NIR pc-LEDs were synthesized by integrating the developed phosphor with a commercial 460 nm blue chip, exhibiting a photoelectric efficiency of 8.5% at 100 mA and a NIR output power of 28 mW at 100 mA. By spin-coating with Ba_8.28Sr_0.72Sc₂Si₆O₂₄:0.01Cr³⁺ phosphor, the relative conversion efficiency of the c-Si solar cell is increased by 31.2% compared to the bare c-Si solar cell. Furthermore, this work presents a novel insight to enhance the luminescence intensity of Cr³⁺ by inhibiting energy transfer in the coexistence system of Cr³⁺ and Cr⁴⁺.