Highly Efficient and Stable Narrow Band Green Emitting Phosphor of Sb 3+ /Ce 3+ Sensitized Cs 2 NaTbCl 6 for WLED

Realizing narrow‐band green phosphors with high efficiency and thermal stability remains an enormous challenge for light‐emitting diodes (LEDs) backlighting in the pursuit of wide‐gamut display. Inspired by excellent and characteristic green sharp line emission of rare‐earth ion Tb 3+ , the rare‐earth‐based halide double perovskite Cs 2 NaTbCl 6 phosphor with line‐shape emission (FWHM: ≈7 nm) at 547 nm is developed. The introduction of sensitizers Ce 3+ or Sb 3+ enhanced the quantum yield of Cs 2 NaTbCl 6 to 76% or 90% from 52% due to the strong absorption of sensitizer and efficient energy transfer from sensitizers to Tb 3+ . The phosphors with or without sensitizer express better thermal stability than traditional perovskite, which originated from the phonon assistance, low thermal ionization probability, stronger localization of 4f electrons through the spectrum, and first‐principles calculation. The warm white LED fabricated using the present green emitting phosphor exhibits low color temperature of 3081 K and ≈100% of the NTSC gamut, which indicates that the Ce 3+ or Sb 3+ sensitized Cs 2 NaTbCl 6 phosphors possess great application potential in WLED illumination and display fields.