Spectral studies of thermally stable Dy3+/Sm3+ co-doped Li2Ba5W3O15 phosphors for warm white LEDs

Abstract In the current study, a series of Li2Ba5W3O15: RE3+ (RE=Dy, Sm) [LBW:Dy3+/Sm3+] phosphors were prepared using a high-temperature solid-state method. X-ray diffraction (XRD), Scanning electron microscopy (SEM) with Energy-dispersive X-ray analysis (EDX) scans showed that the crystal form was consistent with the standard LBW and comprised small irregularly shaped particles. Diffuse reflectance spectral (DRS) data was utilized to calculate the band gaps. Fluorescence study shows that LBW material doped with Dy3+ and Sm3+ yield distinct colors at 496 nm (blue) for Dy3+ and 582 nm (green-yellow), 612 nm (yellow), and 669 nm (red) for Sm3+ when excited by near-ultraviolet (n-UV) (336 nm) light. The observation of energy transfer (ET) between Dy3+ and Sm3+ ions play a role in modifying the luminescence of LBW:Dy3+/Sm3+ co-doped phosphors. With a constant excitation wavelength (λEx), different levels of activator doping lead to a change in the emission colors from their neutral white light to a deep orange-red region for LBW:Dy3+/Sm3+ phosphors. The decay curves demonstrate a decrease in lifetime with an increase in the concentration of activator ions (Sm3+). For D3S5 phosphor, the temperature-dependent photoluminescence (TDPL) characteristics were analysed under λEx = 336 nm excitation. The results indicate excellent luminescence thermal stability with an activation energy of 0.16 eV at λEx = 336 nm. With its low color-correlated temperature (CCT) and good thermal stability, the prepared phosphor sample shows potential as a solid-state emitting phosphor that can be used with UV chip stimulation for warm white LED applications.