Transition metal ion co-doped MgO–MgF2-GeO2:Mn4+ red phosphors for white LEDs with wider color reproduction gamut
- Authors
- Park, Hyun Woo; Jo, Hongil; Anoop, Gopinathan; Yoo, Jae Soo
- Issue Date
- Mar-2020
- Publisher
- Elsevier BV
- Keywords
- BT.2020; MgO–MgF2-GeO2; Mn4+ activated red phosphors; Solid-state lighting; White LEDs
- Citation
- Journal of Alloys and Compounds, v.818
- Journal Title
- Journal of Alloys and Compounds
- Volume
- 818
- URI
- https://scholarworks.bwise.kr/cau/handle/2019.sw.cau/37553
- DOI
- 10.1016/j.jallcom.2019.152914
- ISSN
- 0925-8388
1873-4669
- Abstract
- Mn4+- activated non-rare-earth based red phosphors are excellent down conversion materials for phosphor-converted light-emitting diode (pc-LEDs) based solid-state lighting applications. However, the low quantum efficiency of Mn4+ activated red phosphors under InGaN based blue LED excitation hinders their use in phosphor-converted LEDs. To enhance the absorption at an excitation wavelength of around 420 nm in Mn4+-doped MgO–MgF2-GeO2 (MGF: Mn4+), which is a conventional red-emitting lamp phosphor, we doped MGF: Mn4+ phosphors with transition metal oxides (Sc2O3, Lu2O3, Y2O3, and La2O3) replacing MgO. When excited using 420 nm light, the absorption ratio of the synthesized phosphors with Sc2O3 (Sc-MGF:Mn4+) was 58% with an internal quantum efficiency (IQE) of 55% as compared to the 35% IQE of the pristine MGF-Mn4+ phosphor. White LEDs were fabricated using Sc-MGF-Mn4+ (red), and β-SiAlON:Eu2+ (green) on InGaN chips (λem = 450 nm) and their performance was compared to the optical performance of LEDs fabricated using K2SiF6:Mn4+ as the red phosphor. According to the National Television System Committee (NTSC) standard, the color reproduction coverage with an Sc-MGF:Mn4+ phosphor-loaded white LED was 121% by the International Commission on Illumination (CIE) 1976, and 80% by the BT.2020 standard. The coverages are 9% and 6% higher than the coverages of LEDs fabricated using K2SiF6:Mn4+ as the red phosphor according to the NTSC and BT.2020 standards, respectively. Our simple approach to enhance the IQE of Mn4+ activated phosphors by co-doping transition metal oxides can be extended to other Mn4+ activated phosphor systems for applications that require enhanced absorption, higher luminescent emission intensity, and a wider gamut of color reproduction. © 2019 Elsevier B.V.
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