Study on energy transfer in Ce3+/Sm3+ activated LaSi3N5 phosphor for warm white-light LED

https://doi.org/10.1016/j.physb.2021.413393Get rights and content

Highlights

  • This study provides an strategy for improving the emission efficiency of LaSi3N5:Sm3+.

  • The energy transfer mechanism from Ce3+ to Sm3+ was analyzed.

  • The maximum of energy transfer efficiency can reach 65.5%.

Abstract

Sm3+, Ce3+ singly doped and Ce3+-Sm3+ co-activated LaSi3N5 were synthesized by a solid-state reaction method. The crystal structure, morphology and luminescent properties of the corresponding samples are characterized. The photoluminescence results demonstrate that LaSi3N5:Ce3+ phosphor has a broad band excitation spectra and emission spectra with peak at 418 nm, while LaSi3N5:Sm3+ phosphor demonstrates characteristics of linear excitation spectra with main peak locating at 407 nm. An apparent spectral crossover between the emission spectrum of LaSi3N5:Ce3+ and excitation spectrum of LaSi3N5:Sm3+ can be observed, pointing to the possibility of energy transfer from Ce3+ to Sm3+, which is further proved by the investigations of diffuse reflectance spectra, emission spectra, and fluorescence lifetime decay curves. The energy transfer efficiency reaches the maximum of 65.5%. The mechanism of energy transfer was determined to be electric dipole-dipole interaction. This study provides a new example for the development of efficient phosphors in Ce3+- Sm3+ codoped nitrides.

Introduction

Attribute to its low energy consumption, extra long service life and environmentally, white light emitting diodes (w-LEDs) as a green lighting source have gained much attention but still associated with some foremost drawbacks. At present, the prevailing commercial way to achieve white light emission is adopting a blue light emitting chip to stimulate Y3Al5O12:Ce3+ (YAG:Ce3+) yellow phosphor [1,2]. However, the shortcomings of a high correlated color temperature (CCT, Tc > 4500 K), a weak color rendering index (CRI, Ra < 80) and the harm from bright blue light generated by InGaN chips have limited their further application [[3], [4], [5]]. As an alternative, a near-ultraviolet (n-UV) LED (360–410 nm) encapsulated with blue, green and red phosphors have been emerged as a promising choice due to their excellent color quality [6,7]. Thereby, novel UV-converted tricolor phosphor materials with suitable emission spectra have been developed.

As we know, the yellow and green phosphor in the UV-converted trichromatic phosphors basically meet the requirements of industrial applications [[8], [9], [10]], but the research about red phosphors is still scarce [11,12]. Therefore, it is necessary to make great efforts for the development of red emitting phosphors. As an alternative, Sm3+ ions is always selected as an activator of orange-red luminescent materials in the range of wavelengths longer than 560 nm because of its uppermost 4G5/2-6HJ (J = 5/2, 7/2, 9/2, 11/2) transitions of the 4f5 electronic configuration [[13], [14], [15]]. Therefore, Sm3+ ions can be regarded as a promising dopant for compensating the red composition. However, owing to the self-quenching among coterminous Sm3+ ions, the fluorescence intensity of Sm3+ is usually weak [16,17]. Fortunately, the luminescence intensity of activated ions can be effectively improved by introducing a sensitizer. As a highly efficient sensitizer, energy transfer from Ce3+ to Tb3+, Dy3+, Mn2+ have been extensively studied [[18], [19], [20]], while the research on energy transfer from Ce3+ to Sm3+ is rarely reported.

Due to the firm and rigid network frameworks built up from [SiN4] tetrahedra, lanthanum silicon nitride LaSi3N5 [21,22] has a unique structure with high thermal and chemical stability, which enables them to become potential host for doping of rare earth ions. So far, Ce3+-doped LaSi3N5 (LSN) samples have been reported by several authors, the emission of which is usually in the range of 350–500 nm, in reasonable agreement with the excitation wavelength (∼400 nm) of Sm3+. Therefore, Ce3+, Sm3+ activated and Ce3+/Sm3+ co-activated LaSi3N5 phosphors were successfully designed and synthesized in this work. The structural performance, photoluminescence properties and the process of energy transfer were studied in detail. The red component of the spectrum is enhanced by the energy transfer between Ce3+ and Sm3+, which provides a new idea for the development of phosphors with Sm3+ as activator.

Section snippets

Experimental and characterization

Various Ce3+, Sm3+ doped and co-activated LSN phosphors with different levels of doping were sintered by the solidstate reaction. According to the nominal chemical formulas LSN: xCe3+ (x = 0.04, 0.07, 0.10, 0.13, 0.16), LSN: ySm3+ (y = 0.01, 0.03, 0.05, 0.07, 0.10) and LSN: 0.02Ce3+, ySm3+ (y = 0.01, 0.03, 0.05, 0.07, 0.10), all raw materials LaSi, α-Si3N4, CeF3 and Sm2O3 were weighed by the stoichiometric amount and mixed thoroughly in the agate mortar and transfer to molybdenum crucible.

Phase analysis and crystal structure

The XRD patterns and some main crystal planes of representative LSN: 0.1Ce3+, LSN: 0.03Sm3+, LSN: 0.02Ce3+, 0.03Sm3+ and LSN: 0.04Ce3+, 0.03Sm3+ samples are demonstrated in Fig. 1. Except LSN:0.03Sm3+, all the Bragg diffraction peaks of the specified samples are coincided with the standard card No.42-1144 [23], indicating that neither the Ce3+ single doping nor the Ce3+, Sm3+ co-doping does not conspicuously effect on the phase purity and crystal structure. However, there are some peaks of Si3N4

Conclusions

This work synthesized LSN: xCe3+, ySm3+ (0 ≤ x ≤ 0.16, 0 ≤ y ≤ 0.10) phosphors by the conventional high temperature solid-state reaction. Trivalent cerium and samarium activators are successfully doped into the LSN host and shown isostructural to the parent compound with the P212121 space group. The optical properties of Ce3+ doped LSN, Sm3+ doped LSN and Ce3+, Sm3+ co-doped LSN phosphors are examined using PLE, PL and diffuse reflectance spectroscopy. Comparing the PLE and PL spectra of LSN:

Credit author statement

Fu Du: Writing- Reviewing and Editing. Jinfen Kuang: Data curation, Writing – original draft. Lei Chen: Visualization, Investigation. Yanfei Xiao: Project administration, Conceptualization, Methodology, Software. Lili Liu: Formal analysis. Jiaqing Peng: Supervision.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This work is supported by the cultivation project of the State key Laboratory of Green Development and High-value Utilization of Ionic Rare Earth Resources in Jiangxi Province (20194AFD44003), Ganzhou Science and Technology Key Research and Development Program [2020]60, the National Natural Science Foundation of China (51802203), Shenzhen Science and Technology Research and Development Fund (JCYJ20180306170604395).

References (45)

  • P.I. Paulose et al.

    Sensitized fluorescence of Ce3+/Mn2+ system in phosphate glass

    J. Phys. Chem. Solid.

    (2003)
  • G. Blasse

    Energy transfer in oxidic phosphors

    Phys. Lett. A.

    (1968)
  • L. Vijayalakshmi et al.

    Dazzling cool white light emission from Ce3+/Sm3+ activated LBZ glasses for W-LED applications

    Ceram. Int.

    (2018)
  • K.L. Qiu et al.

    Reverse effect of Sm3+ on Ce3+ in Ca2BO3Cl:Ce3+/Tb3+/Sm3+ phosphor: luminescence, energy transfer and occupation site

    (2019)
  • T. Suehiro et al.

    Synthesis and photoluminescent properties of (La,Ca)3Si6N11:Ce3+ fine powder phosphors for solid-state lighting

    ACS Appl. Mater. Interfaces

    (2011)
  • H. Daicho et al.

    A novel phosphor for glareless white light-emitting diodes

    Nat. Commun.

    (2012)
  • J.H. Oh et al.

    Synthesis of narrow-band red-emitting K2SiF6:Mn4+ phosphors for a deep red monochromatic LED and ultrahigh color quality warm-white LEDs

    J. Mater. Chem. C

    (2015)
  • M. Peng et al.

    Site occupancy preference, enhancement mechanism, and thermal resistance of Mn4+ red luminescence in Sr4Al14O25:Mn4+ for Warm WLEDs

    Chem. Mater.

    (2015)
  • H. Ming et al.

    Highly regular, uniform K3ScF6:Mn4+ phosphors: facile synthesis, microstructures, photoluminescence properties, and application in light-emitting diode devices

    ACS Appl. Mater. Interfaces

    (2018)
  • S. Li et al.

    Data driven discovery of full-visible-spectrum phosphor

    Chem. Mater.

    (2019)
  • J. Yan et al.

    Crystal structure and photoluminescence tuning of novel single-phase Ca8ZnLu(PO4)7:Eu2+,Mn2+ phosphors for near-UV converted white light-emitting diodes

    J. Mater. Chem. C

    (2019)
  • S. Li et al.

    Achieving high quantum efficiency narrow-band β-Sialon:Eu2+ phosphors for high-brightness LCD backlights by reducing the Eu3+ luminescence killer

    Chem. Mater.

    (2017)
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