Sb 3+ –Er 3+ ‐Codoped Cs 2 NaInCl 6 for Emitting Blue and Short‐Wave Infrared Radiation

Cs 2 NaInCl 6 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 Cs 2 NaInCl 6 by codoping Sb 3+ ( s ‐electron doping) and Er 3+ ( f ‐electron doping) ions. Sb 3+ doping introduces optically allowed 5 s 2 5 s 1 5 p 1 electronic absorption at the sub‐band gap level, which then emits blue photoluminescence with ≈93 % quantum yield. But f‐f electronic absorption of Er 3+ is parity forbidden. Codoping Sb 3+ –Er 3+ , leads to transfer of excitation energy from Sb 3+ to Er 3+ , 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.