Optical absorption intensity analysis using Judd-Ofelt theory and photoluminescence investigation of orange-red Sr2SiO4: Sm3+nanopigments

Abstract

The Orange-red emitting Sr2SiO4:xSm3+ (x = 0.01–0.09) nanopigments for white light emitting diodes (w-LED's) were prepared by low temperature solution combustion route. Systematic investigations on structural and photoluminescence properties were done with respect to activator concentration (Sm3+). The Judd-Ofelt (JO) intensity parameters that are very significant for the evaluation of laser and luminescent materials are calculated based on the quantitative absorption spectra. This approach for calculating JO parameters are particularly important since the proportional relation between absorption and emission intensities are considered. JO intensity parameters (Ω2, Ω4 and Ω6) were calculated for the sample Sr2-xSmxSiO4 (x = 0.03) for which the emission observed was maximum. These parameters followed the trend Ω2 > Ω6 > Ω4. The visible emission spectrum and JO parameters indicate that the structural environment surrounding the rare earth ions is centrosymmetric in nature. The effect of Sm3+ ion doping concentrations on the luminescent behaviour were investigated in detail using non-radiative energy transfer mechanism. Branching ratio and emission cross section are critical parameters in laser design which in our case are found to be 67% and 3.82 × 10−22 cm2 respectively for the transition 4G5/2 → 6H7/2. Thus, the phosphor can be potentially used for modelling of laser systems and red component as well may be utilised for white light emitting diodes in solid state lightning applications.