Compositionally Tuned Self-Activated Alkali Metal Vanadates for High Color Rendering White LEDs and IR Reflective Pigments

Abstract

Phosphor-converted white light-emitting diodes (pc-WLEDs) with a supreme color rendering index (CRI) remain challenging, particularly due to the limited accessibility of efficient cyan-green-emitting phosphors in the 480–520 nm emission range. Herein, a novel rare earth-free cyan-green-emitting Ta5+-substituted CsVO3 phosphor that exhibits a VO43– charge transfer enabled cyan-green emission band centered at ∼520 nm under the 370 nm near UV (n-UV) light is reported with an internal quantum efficiency of 93.9%. This cyan-green emission profile could align well with the broad-band yellow-orange emission to produce high CRI warm white light. Such yellow-orange emission spectra are achieved by incorporating Cs+ ions into the Rb3V5O14 system, which tunes the emission color from red to orange and eventually to yellow. Furthermore, the light absorption in Rb3–xCsxV5O14 was followed by internal energy transfer from the 2p O2– to the 3d V5+ orbitals, resulting in perceived pigment-type colors ranging from red to yellow with promising NIR reflectance. When combined strategically, they can be excited by n-UV light and generate a well-distributed white light with an impressive CRI of 89 and a low color temperature (CCT) of 4056 K. These findings suggest that the newly developed rare earth-free vanadates hold promise for use in full-spectrum pc-WLEDs.