Evolution of highly efficient rare-earth free Cs(1−x)RbxVO3 phosphors as a single emitting component for NUV-based white LEDs

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2018, Vol.6 (46), p.12746-12757
• Main Authors: Pavitra, E, G Seeta Rama Raju, Bharat, L Krishna, Jin Young Park, Kwak, Cheol Hwan, Chung, Jong Won, Young-Kyu, Han, Huh, Yun Suk
• Format: Article
• Language: English
• Subjects: Cesium ions; Commercialization; Diffraction patterns; Diodes; Forbidden transitions; Illumination; Lighting; Luminescence; Luminous efficacy; Near ultraviolet radiation; Optical properties; Organic light emitting diodes; Phosphors; Rare earth elements; Sol-gel processes; Tetrahedra; White light; X-ray diffraction
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/c8tc05110k

Since the commercialization of white light-emitting diodes (WLEDs) in 1996, they are rapidly replacing conventional lighting sources and have become an essential commodity for day-to-day human life. At present, most of the WLEDs existing in the market are rare-earth based, which are very limited, expensive and often not available due to monopolistic supply conditions. Hence, there is a serious demand for novel rare-earth free phosphors to achieve cost-effective and energy-efficient WLEDs with excellent luminous efficacy for general illumination. Herein we report on highly efficient rare-earth free Cs(1−x)RbxVO3 phosphors as a single emitting compound for near UV-based WLEDs manufactured by the citrate sol–gel method for the first time. Rietveld refinement is performed for the X-ray diffraction patterns of the CsVO3 host and CsVO3:0.25Rb phosphors to reveal their orthorhombic pyroxene structure. The difference in the ionic radii of Rb+ and Cs+ ions led to a more distorted VO43− tetrahedron with a broken Td symmetry, which allows spin forbidden transitions for CsVO3:0.25Rb phosphors, resulting in enhanced internal and external quantum efficiencies of 94.7% and 84.5% along with superior luminescence properties compared to the CsVO3 host. When varying the input current from 20 to 200 mA, the fabricated WLED exhibited a good color rendering index of 69.7–81.5 and an extremely high luminous efficacy of 94.8–58.7 lm W−1, which are among the highest values for the same host lattice. These rare-earth free CsVO3:0.25Rb phosphors with a single emitting center may emerge as a new class of advanced inorganic phosphors for near UV-based WLEDs in the lighting industries.