Sr-substitution-guided Eu2+ site engineering of Ca9Nd(PO4)7:Eu2+ for high-efficiency white light-emitting diodes

The phosphor-converted white light-emitting diodes (pc-WLEDs) have been regarded as a promising alternative to the traditional light source in the fields of lighting and display. Herein, Ca9_xSrxNd(PO4)(7): Eu2+ phosphor with moderately broadband ed emission was successfully designed and synthesized based on Ca9Nd(PO4)(7). The X-ray diffraction (XRD) patterns ensure the phase purity of the materials. Further XRD Rietveld refinements were performed to shed light on the Sr/Ca substitution impact and the site occupations induced by intentionally introduced Sr. The site strategy was proved to be feasible along with the Sr/Ca3 and sequentially Eu/Sr preferable occupations, which leads to confined regulation of the Eu luminescent in the host. Theoretical simulations based on density functional theory (DFT) suggest a good potential of the materials as hosting matrices of Eu2+ before and after Sr/Ca substitution, while the site preference was proved from the theoretical aspect as well. At last, the materials were coated onto a near-ultraviolet (n-UV) commercial LED chip to fabricate a pc-WLED with warm white-light emission and high color rendering index (Ra). The prototype pc-WLED also survived a long-term stability test and current-dependent test to show great potential in practical application.