Study on energy transfer in Ce3+/Sm3+ activated LaSi3N5 phosphor for warm white-light LED

Abstract Sm3+, Ce3+ singly doped and Ce3+-Sm3+ co-activated LaSi3N5 were synthesized by a solid-state reaction method. The crystal structure, morphology and luminescent properties of the corresponding samples are characterized. The photoluminescence results demonstrate that LaSi3N5:Ce3+ phosphor has a broadband excitation spectra and emission spectra with peak at 418 nm, while LaSi3N5:Sm3+ phosphor demonstrates characteristics of linear excitation spectra with main peak locating at 407 nm. An apparent spectral crossover between the emission spectrum of LaSi3N5:Ce3+ and excitation spectrum of LaSi3N5:Sm3+ can be observed, pointing to the possibility of energy transfer from Ce3+ to Sm3+, which is further proved by the investigations of diffuse reflectance spectra, emission spectra, and fluorescence lifetime decay curves. The energy transfer efficiency reaches the maximum of 65.5%. The mechanism of energy transfer was determined to be electric dipole-dipole interaction. This study provides a new example for the development of efficient phosphors in Ce3+- Sm3+ codoped nitrides.