Influence of Mn2+ doping on the optical properties of Cs2AgBiCl6 double perovskite luminescent phosphors

Lead free double perovskites have emerged as a highly stable alternatives to organic–inorganic halide perovskites in recent years. In this work, we have successfully endowed weakly luminescent Cs 2 AgBiCl 6 double perovskite with strong red luminescence by incorporating Mn 2+ in their lattices. It was also observed that the intensity of red emission increased with increase in Mn 2+ concentration. Electron paramagnetic resonance (EPR) and energy dispersive X ray spectroscopy manifest the presence of isolated Mn 2+ ions in Cs 2 AgBiCl 6 . The obtained hyperfine coupling constant of 90 Gauss from EPR spectra also confirms the octahedral coordination of Mn 2+ ions. Scanning electron micrographs of pure and Mn 2+ doped Cs 2 AgBiCl 6 exhibit octahedral particles. X-ray diffraction patterns of different concentration of Mn 2+ in Cs 2 AgBiCl 6 reveals that all samples crystallize in face centred cubic structure with Fm 3 - m symmetry. The crystallite size and lattice strain were found to increase with increase in Mn 2+ concentration. Detailed changes in structural parameters of Cs 2 AgBiCl 6 upon Mn 2+ doping evaluated using rietveld refinement of XRD spectra indicates a linear decrease in unit cell volume. Raman spectra measurements which divulges a decrease in Ag–Cl and Bi–Cl octahedral volume on introducing smaller size Mn 2+ ion which leads to the overall decrease of unit cell volume. Thermal gravimetric analysis discloses that the Mn 2+ :Cs 2 AgBiCl 6 double perovskites are stable upto 520 °C. This work demonstrates an easy way of tuning the photophysical properties of Cs 2 AgBiCl 6 by transition metal doping and can widen their application prospects in optoelectronics.