Sb³⁺–Er³⁺‐Codoped Cs₂NaInCl₆ for Emitting Blue and Short‐Wave Infrared Radiation

Abstract

Cs₂NaInCl₆ 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 Cs₂NaInCl₆ by codoping Sb³⁺ (s-electron doping) and Er³⁺ (f-electron doping) ions. Sb³⁺ doping introduces optically allowed 5s²→ 5s¹5p¹ 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.