High color rendering index single phase white light emitting phosphors based on Tb3+/Sm3+ co-doped CePO4 nanocrystals: the role of Tb3+ as a bridge between Ce3+ and Sm3+†
Single phase white light emitting CePO4 nanocrystals doped with Tb3+ and Sm3+ were synthesized through a sol gel route for the first time. The single phase monoclinic structure of the samples was confirmed by XRD analysis. FTIR and XPS analysis were used to demonstrate that CePO4 is a good host with a minimum quenching environment. The triple energy transfer processes from Ce3+ to Tb3+, Ce3+ to Sm3+ and Ce3+ to Sm3+via Tb3+ in CePO4 nanocrystals are analyzed by photoluminescence excitation and emission spectra. The role of Tb3+ as a bridge between Ce3+ and Sm3+ ions in CePO4 is systematically studied by varying the concentrations of Tb3+ and Sm3+. The existence of energy transfer channels from Tb3+ to Sm3+ from 5D3 and 5D4 energy levels of Tb3+ is revealed by decay analysis. The CIE chromaticity coordinates, color temperature and high color rendering index suggest that the newly developed cool white light emitting Tb3+ and Sm3+ co doped CePO4 nanocrystals are a potential candidate in the field of white light applications.