Bright and High-Color-Rendering White Light-Emitting Diode Using Color-Tunable Oxychloride and Oxyfluoride Phosphors

Abstract White lighting converted by tricolor phosphor and near-ultraviolet light-emitting diode demonstrates great potential in general lighting. However, a major problem with this approach is the lower luminous efficiency of the resulting white lighting by the reabsorption among tricolor phosphors. In this work, we propose a general but effective method for achieving high-efficacy white light-emitting diodes (WLEDs) by using two-color phosphors having the same host that can lower energy loss by reabsorption. Color-tunable Sr7.95Si4O12Cl8:0.05Eu2+ (SSO_Cl:0.05Eu2+) phosphors are synthesized by cationic substitution strategy, and the emission colors can be tuned from blue-greenish to blue/yellow by Sr → Mg/Ca substitution. The red-shifted emission is attributed to the increased Eu2+ d-orbital splitting owing to the smaller size of Ca2+, whereas blue-shifted Eu2+ emission is unusual in Mg-substitution for Sr2+. WLEDs with luminous efficacies (ηL) of 28.9–56 lm/W and CRIs of 79–90.2 are demonstrated using the two-color phosphors. By employing a narrow-line Mn4+ emission deep red oxyfluoride phosphor, a high CRI (Ra = 90.3, R9 = 94) WLED with ηL of 39.3 lm/W is obtained. These findings provide a possible way for developing high CRI WLED by using two-color phosphors.