Photoluminescence Behavior of Sm³⁺-Doped YPO₄ Phosphors for Solid-State Lighting

Phosphors emitting orange light under ultraviolet (UV) excitation are crucial for enhancing the performance of white light-emitting diodes. In this study, we investigate the photoluminescence properties of Sm³⁺-doped yttrium orthophosphate (YPO₄) phosphors synthesized using the coprecipitation method. X-ray diffraction and Fourier-transform infrared spectroscopy were used to examine the structure and vibrational properties of the synthesized phosphors. By analyzing diffuse reflectance spectra using the Kubelka-Munk theory, the optical bandgap was determined to be 4.03 eV, corresponding to the UV region. Photoluminescence spectra, obtained under 406-nm excitation, showed orange emission at 602 nm, attributable to the ⁴G_5/2 → ⁶H_7/2 transition of Sm³⁺ ions. Dipole-dipole interactions were responsible for the concentration-quenching effect, investigated using Dexter's hypothesis. Photometric and colorimetric investigations were performed to explore the emission behavior of the phosphors. The calculated CIE coordinates confirmed emission in the orange region, and photometric investigations revealed that the phosphor exhibited orange emissions under UV illumination. Overall, this study provides valuable insights into the emission behavior of YPO₄ doped with Sm³⁺ ions, which are essential for assessing their suitability and potential applications for advanced photonic devices.