Insight into the spectroscopic behavior of Dy3+-substituted and Li+ charge-compensated molybdate phosphors

Efficient utilization of phosphors in solid-state lighting and phosphor-converted light-emitting diodes demands high emission intensity, narrow size distribution, and tunable luminescence. Here in this work, un-doped and Li+ co-doped CaMoO4:Dy3+ nanoparticles are synthesized via modified reflux method in ethylene glycol medium at 130 degrees C. The host shows broad dual band emission centered in blue and green regions endowed by charge transfer and defects. Upon Dy3+ doping, the host-to-dopant energy transfer causes the CaMoO4:Dy3+ nanoparticles to exhibit characteristic emission lines from Dy3+. The Commission Internationale de L'Eclairage (CIE 1931) chromaticity coordinates for the prepared phosphors are estimated and found to lie in the nearly white region of color space. The light output as well as excited state lifetimes are successfully improved by lithium co-doping by virtue of reduced charge compensating defects and sensitization via oxygen-related defects. The positron annihilation studies show that all the lithium concentration co-doped for charge compensation is merely helping in the removal of cations. This work shows the role of lithium co-doping and its optimum concentration in improving the optical properties of phosphors.

Automated summary

This study demonstrates the efficient utilization of phosphors in solid-state lighting and phosphor-converted light-emitting diodes through the synthesis of undoped and Li+ co-doped CaMoO4:Dy3+ nanoparticles. The characteristic emission lines from Dy3+ are achieved through energy transfer from the host to the dopant. The optical properties of the phosphors are improved by lithium co-doping, resulting in enhanced light output and excited state lifetimes. This work highlights the importance of lithium co-doping in enhancing the optical properties of phosphors.