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Eu(II)‐Activated Silicates for UV Light‐Emitting Diodes Tuning into Warm White Light
Author(s) -
Bispo-Jr Airton G.,
Lima Sergio A. M.,
Carlos Luís D.,
Pires Ana M.,
Ferreira Rute A. S.
Publication year - 2020
Publication title -
advanced engineering materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.938
H-Index - 114
eISSN - 1527-2648
pISSN - 1438-1656
DOI - 10.1002/adem.202000422
Subject(s) - phosphor , luminous efficacy , materials science , color rendering index , color temperature , light emitting diode , optoelectronics , diode , solid state lighting , led lamp , luminous flux , luminous intensity , optics , nanotechnology , light source , physics , layer (electronics)
White‐light‐emitting diodes (WLEDs) are the main white light source for general lighting due to high‐luminous efficacy (>150 lm W −1 ), long lifespan (5 × 10 4 h), and environmentally friendly properties. Despite the current maturity and reliability of the solid state‐lighting field, the control of the correlated color temperature (CCT) tuning is still a challenge, arising from the lack of red emission color in the current design of commercial WLEDs. Moreover, as this aspect is often associated with dysregulations of the human circadian rhythm, the need for novel WLEDs is of enlarged societal relevance. In this scope, herein, warm WLED prototypes are fabricated by coating near‐UV‐emitting LEDs with a mixture of the yellow‐emitting polyphasic Sr 2 SiO 4 :Eu(II) (S2S) and the blue‐emitting BaMgAl 10 O 17 :Eu(II) (BAM) phosphors dispersed in poly(methyl methacrylate). As the amount of S2S increases in the phosphor mixture, the CCT values of the WLEDs decrease from 6500 K (ideal for daylight application) to 4000 K (ideal for night light application), with a luminous efficacy of radiation of 404 lm W −1 , among the best figures of merit for WLEDs. Furthermore, all the WLED devices also display a desirable color rendering index (CRI > 75), comparable with the commercial WLED, independent on the operating voltage.