Chloride Double Perovskites Doped With Sb³⁺/Er³⁺ as Stable and Effective Luminescence Material in the Vis-NIR Region

The luminescence properties of stable chloride double perovskites Cs₂B^IInCl₆, where B^I is 4 at.% Ag, 6 at.% Na, doped with Sb³⁺ and Er³⁺  were investigated for the first time in the 250-1600 nm region and revealed significant potential for advanced application. We employed XPS and ToF-SIMS for chemical analyses, while SEM, XRD, and Raman spectroscopy provided insights into the morphology, crystal structure, and vibrational characteristics of the samples. The crystal structures of Cs₂Ag_0.292Na_0.708InCl₆, Cs₂Ag_0.285Na_0.715In_0.971Er_0.029Cl₆, Cs₂Ag_0.16Na_0.84In_0.893Er_0.017Sb_0.09Cl₆ were examined using single-crystal methods. The excited Sb³⁺ ions emitted blue light at 450 nm due to electronic absorption at sub-band gap levels, facilitating energy transfer to Er³⁺ ions. Notably, the Er³⁺ emitted radiation at 1540 nm, a wavelength particularly useful for optical communication applications. Additionally, emissions at 525 nm, 552 nm, 665 nm, and 805 nm were observed, corresponding to f-f transitions of Er³⁺ ions. These compelling results were supported with calculations based on the Modified Crystal Field Theory, explaining the effects of varying concentrations of Sb³⁺ and Er³⁺ on the crystal structure and luminescent properties. By using the synthesized materials, we successfully developed an LED prototype that utilized a UV chip (320 nm) combined with the Cs₂Ag_0.4Na_0.6In_0.9Er_0.01Sb_0.09Cl₆ powder as a stable and effective luminophore for possible application in optoelectronics.