White-emitting silicates doped with lanthanide and transition metal ions for application in warm white-light-emitting diodes

Abstract

White-light-emitting diodes (WLEDs) are currently the main white light sources for lighting, traffic light or backlighting of displays due to their long lifespan (50,000 h), brightness (800 lm) and luminous efficacy (150 lm·w-1), low power consumption (8.5 W), coast-benefit (60 dollars over 20 years of use) and environmentally friendly properties compared to incandescent and fluorescent lamps. However, some drawbacks related to the quality of the white color still need to be addressed since the main commercially available WLED features a blueish white color, classified as cool white color that is dangerous to humans considering the circadian rhythm regulation. To overcome such issues, new strategies based on the fabrication of WLEDs by combining near-UV-emitting LEDs and single-phased white-emitting phosphors have emerged within the solid-state lighting field. In this case, the main challenges lie on the synthesis of phosphors that match high emission quantum yield (> 50 %), high thermal stability of luminescence and emission of white color featuring high color rendering index (> 90) and low correlated color temperature (3.000 K) ideal for nigh lighting. Thus far, this project deals with the synthesis of new single-phased white-emitting phosphors based on Sr3SiO5 or Ca2MgSi2O7 doped with Ce3+, Tb3+ and Eu3+ or Ce3+, Eu2+ and Mn2+, aiming to take advantage of the blue emission of Ce3+, green emission of Tb3+ and red emission of Eu3+ or the blue emission of Ce3+, green emission of Eu2+ and red emission of Mn2+ within these hosts. Ce3+ also acts as sensitizer for the Eu3+, Tb3+ and Mn2+ luminescence. The main challenge of this propose is the optimization of the doping concentration in order to favor the energy transfer processes, leading to the emission of white light featuring high emission quantum yield. The phosphors will be combined with near-UV-emitting LEDs, fabricating WLEDs displaying correlated color temperature (< 3.500 K), color rendering index (> 90) and luminous efficacy (> 100 lm·W 1) required for applications of warm WLEDs in night lighting. (AU)