Enhancement of self-trapped excitons and near-infrared emission in Bi 3+ /Er 3+ co-doped Cs 2 Ag 0.4 Na 0.6 InCl 6 double perovskite.

Erbium (Er) complexes are used as optical gain materials for signal generation in the telecom C-band at 1540 nm, but they need a sensitizer to enhance absorption. Na + substitution for Ag + and Bi 3+ doping at the In 3+ site is a possible strategy to enhance the broadband emission of Cs 2 AgInCl 6 , which could be used as a sensitizer for energy transfer to rare-earth elements. Herein, self-trapped exciton (STE) energy transfer to Er 3+ at 1540 nm in double perovskite is reported. An acid precipitation method was used to synthesize Cs 2 AgInCl 6 and its derivatives with Er 3+ , Bi 3+ , and Na + . Bare Cs 2 AgInCl 6 :Er emission signals were found to be weak at 1540 nm, but Bi 3+ doping increased them by 12 times, and Bi 3+ and Na + doping increased signal intensity by up to 25 times. Electron paramagnetic resonance spectroscopy characterized a decrease in axial symmetry over the Er 3+ ions after the substitutions of Na + and Bi 3+ in Cs 2 AgInCl 6 at low temperatures (<7 K) for the first time. Moreover, an increase in pressure compressed the structure, which tuned the STE transition for free exciton emission, and a further increase in pressure distorted the cubic phase above 70 kbar.