Sb³⁺ -Er³⁺ -Codoped Cs₂ NaInCl₆ for Emitting Blue and Short-Wave Infrared Radiation

Cs₂ NaInCl₆ double perovskite is stable, environmentally benign and easy to prepare. But it has a wide band gap (5.1 eV), and therefore, does not show optical and optoelectronic properties in the visible and short-wave infrared (SWIR) region. Here we introduce such functionalities in Cs₂ NaInCl₆ by codoping Sb³⁺ (s-electron doping) and Er³⁺ (f-electron doping) ions. Sb³⁺ doping introduces optically allowed 5s² $$ 5s¹ 5p¹ electronic absorption at the sub-band gap level, which then emits blue photoluminescence with ≈93 % quantum yield. But f-f electronic absorption of Er³⁺ is parity forbidden. Codoping Sb³⁺ -Er³⁺ , leads to transfer of excitation energy from Sb³⁺ to Er³⁺ , yielding SWIR emission at 1540 nm. Temperature (6 to 300 K) dependent photoluminescence measurements elucidate the excitation and emission mechanism. A phosphor converted light emitting diode (pc-LED) fabricated by using the codoped sample emits stable blue and SWIR radiation over prolonged (84 hours) operation at 5.1 V.