Journal
CHEMICAL ENGINEERING JOURNAL
Volume 405, Issue -, Pages -Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.cej.2020.126678
Keywords
Light-emitting diodes; Moisture resistance; Mn4+; Self-protection; Photoluminescence
Categories
Funding
- National Natural Science Foundation of China [51802359, 21801254, 51902354]
- Joint Fund of Yunnan [U1702254, U1801253]
- Joint Fund of Guangdong Province [U1702254, U1801253]
- Special Fund of Guangdong Province Project for Applied Science and Technology Research and Development [2017B090917001]
- Guangdong Basic and Applied Basic Research Foundation [2020A1515010556]
- Fundamental Research Funds for the Central Universities [19lgpy123]
- China Postdoctoral Science Foundation
- National Recruitment Program of Highend Foreign Experts [GDT20185200479, GDW20145200225]
- Programme for the Foreign Experts [W2017011]
- Wenfeng High-end Talents Project by Chongqing University of Posts and Telecommunications (CQUPT) [W2016-01]
- Estonian Research Council [PUT PRG111]
- European Regional Development Fund [TK141]
- [2019M663230]
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Mn4+-activated oxyfluoroniobate phosphor (Cs2NbOF5) with internal quantum efficiency of approximately 82% has shown remarkably improved waterproof stability even without surface coating compared to commercial fluoride red-emitting phosphor. The presence of Nb5+ ions inside the phosphor plays a crucial role in enhancing the water-resistant performance of Mn4+, offering a new concept for overcoming the waterproof downside in humid conditions while maintaining luminescence efficiency. White LEDs fabricated using Cs2NbOF5:Mn4+ demonstrate high luminous efficacy (174 lm/W) and excellent color rendering properties.
Mn4+-activated fluoride red phosphors, the most important red phosphors for warm white light emitting diodes (LEDs), usually suffer from inherent poor moisture resistance which is a major obstacle to their long-lasting outdoor applications in a high humidity environment. Surface modification of phosphors by coating with either organic or inorganic shells is an effective way to improve waterproof stability. However, the coating procedure usually has a negative impact on the luminous efficacy due to the increased passivation shell thickness. In this work, Mn4+-activated oxyfluoroniobate (Cs2NbOF5), a highly efficient phosphor with internal quantum efficiency of ca. 82%, has been successfully synthesized and it is interesting to note that Cs2NbOF5:Mn4+ can exhibit remarkably improved waterproof stability even without surface coating compared to well-accepted commercial fluoride red-emitting phosphor, K2SiF6:Mn4+. The results obtained indicate that Nb5+ ions inside red phosphor play a crucial role in improving the water-resistant performance of Mn4+, which provides a new concept for overcoming the downside of their waterproof in humid conditions and maintaining the luminescence efficiency. In the final phase white LEDs with a high luminous efficacy of 174 lm/W (higher than commercial fluoride red phosphors), low correlated color temperature (3164 K) and high color rendering index (R-a = 90 and R-9 = 85) have been fabricated using Cs2NbOF5:Mn4+.
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