Mingcai Li,Xuejie Zhang,Yinjian Zheng,Yaliang Xu,Haoran Zhang,Yingliang Liu,Bingfu Lei
The discovery of light converter excited by near-ultraviolet (UV) superior broadband blue-emitting lighting source is a main challenge in plant growth LEDs. In this study, SrLu 2 O 4 :Ce 3+ , Li + , F − blue phosphor has been synthesized via a solid-state reaction. Benefitting from doping of F − ions, SrLu 2 O 4 :Ce 3+ , Li + , F − phosphor (λ ex = 405 nm, λ em = 460 nm) shows a strong broadband (FWHM = 90 nm) blue-emitting with lower critical concentration of Ce 3+ ions and an increasing 6.9% thermal quenching performance (92.1% @ 423 K of the peak intensity at room temperature). Moreover, a blue light converter composed of SrLu 2 O 4 :Ce 3+ , Li + , F − phosphor and glass matrix is obtained based on phosphor-in-glass (PiG) technology, exhibiting excellent thermal stability and outstanding moisture resistance . A red light converter with commercial red phosphor is obtained by the same method. Furthermore, by combining of two light converters with near-UV chip, a proof-of-concept plant growth high power LED is achieved and applied in indoor Italian lettuce growing in comparison with commercial plant lamps.
The exploration of stable/efficient phosphor for n -UV chip pumped white light-emitting diodes ( w LEDs) remains an arduous task. Herein, a novel series of color tunable Eu 2+ /Tb 3+ /Sm 3+ tridoped Sc-based cyclosilicate phosphors (KBaScSi 3 O 9 : Eu 2+ /Tb 3+ /Sm 3+ ) have successfully designed and obtained via facile solid-state reaction based on comprehensive consideration of rigidly structural network of host, weak electron-phonon coupling strength and spectral adjustability of codopants via energy transfer (ET). The crystallographic occupancies of Eu, Tb and Sm primary in Ba/K, Ba and Ba sites in the monoclinic host, respectively were determined on the basis of the Rietveld refinements and crystal chemistry rules. The photoluminescence (PL) properties were systematically investigated in conjunction with structural analyses, implying that the ‘warm’ white light with excellent thermal stability is stemmed from combination of optimized blue (Eu 2+ ), green (Tb 3+ ) and red (Sm 3+ ) emissions via Eu → Tb → Sm ET strategy. Interestingly, Tb ions play both roles of green light luminescent center and ET bridge to achieve cascade ET for connecting Eu/Sm ion pairs because of the adverse metal-metal charge transfer (MMCT) effect (Eu 2+ + Sm 3+ → Eu 3+ + Sm 2+ ). Furthermore, the phosphor-converted w LEDs (pc- w LEDs), by encapsulating the optimal KBS: 4 %Eu/4 %Tb/6 %Sm with commercial n -UV LED chip, show high thermal stability with satisfactory electroluminescence (EL) performances. These results indicate the KBS: Eu/Tb/Sm phosphors are potential candidates for application in high power n -UV pumped pc- w LEDs.
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