Abstract
A Bi3+ and Eu3+ ion co-doped Ba9Lu2Si6O24 single-phased phosphor was synthesized successfully via a conventional high-temperature solid-state reaction. X-ray diffraction, crystal structure analysis, diffuse reflectance and luminescent spectra, quantum efficiency measurements, and thermal stability analysis were applied to investigate the phase, structure, luminescent and thermal stability properties. From the analyses of the crystal structure and luminescent spectra, we observed four discernible Bi3+ luminescent centers with peaks at ~363.3, ~403.1, ~437.7, and ~494.5 nm. Moreover, due to the complex energy transfer processes among these Bi3+ centers, their relative emission intensity tightly depended on the incident excitation wavelength. Interestingly, the as-prepared phosphor could generate warm white light/tunable emission by changing the concentration of Eu3+ ions or adjusting the excitation wavelength. The energy transfer mechanism from Bi3+ to Eu3+ was confirmed via an electric dipole-dipole interaction, the energy transfer efficiencies ({eta }_{T}) from Bi3+ to Eu3+ were 50.84% and 40.17% monitoring at 410 and 485 nm, respectively. The internal quantum efficiency of the optimized Ba9Lu2Si6O24:Bi3+, Eu3+ phosphor was calculated to be 42.6%. In addition, the configurational coordinate model was carried out to explain the energy decrease of the phonon-electron coupling effect.
Highlights
A Bi3+ and Eu3+ ion co-doped Ba9Lu2Si6O24 single-phased phosphor was synthesized successfully via a conventional high-temperature solid-state reaction
We reported a systematic study on the Bi3+, Eu3+ co-doped BLSO single-phased phosphor with warm white light/tunable emission by manipulating energy transfer in multicentered photoluminescence
Four discernible Bi3+ (Bi(I)- Bi(IV)) luminescent centers were confirmed by analyzing the crystal structure and luminescent spectra
Summary
A Bi3+ and Eu3+ ion co-doped Ba9Lu2Si6O24 single-phased phosphor was synthesized successfully via a conventional high-temperature solid-state reaction. The trichromatic phosphor system produces several inevitable problems, including complex coating, fluorescence reabsorption between different components, and non-uniformity of the luminescence properties, resulting in the degradation of luminous efficiency, increased manufacturing costs and a time-dependent shift of the color point[15,16] To circumvent these drawbacks, a single-phased phosphor, which is fabricated by co-doping the sensitizer and activator ions into an appropriate host, with white light emission for near-UV pumped w-LEDs would be favorable alternative[17]. We studied the multicentered photoluminescence characteristics and site engineering in a Bi3+ and Eu2+ co-doped Ba9Lu2Si6O24 phosphor to realize white light/tunable emission for phosphor-converted w-LEDs. Due to the complex energy transfer processes, the tuning of multicentered photoluminescence can be achieved by adjusting the excitation wavelength or controlling the rare-earth ion concentration
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