Downshifting in Cs2NaBiCl6:Er3+: transforming ultraviolet into near infrared radiation

Abstract

The outstanding assets of stability and non-toxicity have produced a surge of research interest into lead-free double perovskite halides for photovoltaic and optoelectronic applications. Here we report the near infrared (NIR) downshifting of micron and nanoparticle (NP)-size erbium-doped Cs₂NaBiCl₆ under ultraviolet excitation. The 1.54 nm emission of Er³⁺ is obtained by the population of the ⁴I_13/2 level by an internal Er³⁺ temperature-dependent cross-relaxation process and also from bismuth energy transfer. The NIR emission can be switched from sharp to broad band by selective excitation. The doped NPs may be dispersed in organic solvents and the emission intensity can be tuned by choice of solvent.