Facile Preparation and Ultrastable Performance of Single-Component. White-Light-Emitting Phosphor-in-Glass used for High-Power Warm

Transcription

1 Supporting Information For Facile Preparation and Ultrastable Performance of Single-Component White-Light-Emitting Phosphor-in-Glass used for High-Power Warm White LEDs Xuejie Zhang, Jinbo Yu, Jing Wang, *, Chenbiao Zhu, Jinhui Zhang, Rui Zou, Bingfu Lei, YingLiang Liu, and Mingmei Wu, *, Ministry of Education Key Laboratory of Bioinorganic and Synthetic Chemistry, State Key Laboratory of Optoelectronic Materials and Technologies, KLGHEI of Environment and Energy Chemistry, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou, Guangdong , China College of Materials and Energy, South China Agriculture University, Guangzhou, Guangdong , China Corresponding author: S-1

2 Experimental Section Synthesis of phosphors: Ca 9 Gd(PO 4 ) 7 :0.6%Eu 2+,yMn 2+ (y = 0, 1.0, 2.0, 3.0, 4.0, 5.0, 7.0, 10%) (denoted as CGP:Eu 2+,Mn 2+ ) phosphors were synthesized by high-temperature solid-state reaction. The raw materials were CaCO 3 (A.R.), NH 4 H 2 PO 4 (A.R.), Gd 2 O 3 (4N), Eu 2 O 3 (4N), and MnCO 3 (A.R.). The stoichiometric amount of raw materials was thoroughly mixed by grinding in an agate mortar. Then, the powder mixtures were then transferred into crucibles and heated at 1300 C for 2 h in crucibles alone with the carbon and slowly cooled to room temperature. After regrinding, they were resintered at 1300 C for 6 h under a 10% H 2-90% N 2 gas mixture. Finally, the as-synthesized samples were slowly cooled to room temperature inside the tube furnace under H 2 -N 2 flow. Synthesis of phosphor-in-glass (PiG) samples: Precursor glasses with the compositions (mol %) of 30SiO 2-6Al 2 O 3-22B 2 O 3-30ZnO-12BaO were firstly prepared by a conventional melting-quenching method. The corresponding raw materials were mixed and then melted at 1400 C for 1 h in a corundum crucible. Immediately after immersed into water, the melted glass liquid turns into the cullet. They were then dried and milled into glass powders. The as-obtained glass frit was uniformly mixed with CGP:0.6%Eu 2+,yMn 2+ (y = 0, 2.0, 3.0, 5.0, 10%) phosphors. The weight ratio of glass frit to phosphor is fixed at 9:1. Then, a typical 2.5g batch of the mixture was transferred into rubber mold and pressed into cylinder using cold isostatic pressing. After demolding, the cylinders were sintered for 30 min at 700 C in air atmosphere to form CGP:0.6%Eu 2+,yMn 2+ -PiG (y = 0, 2.0, 3.0, 5.0, 10%) samples. The as-synthesized PiG samples were cut and carefully polished for optical measurements. Characterization and measurement: Powder X-ray diffraction was performed on Bruker D8 advance X-ray diffractometer (XRD) with CuKa (λ = Å) radiation at 40 kv and 40 ma. The morphology and elemental composition of the as-prepared samples were measured by SEM (FEI Quanta 400). The photoluminescence excitation (PLE) and photo-luminescence (PL) spectra at the temperature range of RT 200 C as well as the decay curves were measured by FSP920 Time Resolved and Steady State Fluorescence Spectrometers (Edinburgh Instruments, England) equipped with a 450 W Xe lamp, a 150 W nf900 flash lamp, TM300 excitation monochromator and double TM300 emission monochromators and thermo-electric cooled red sensitive S-2

3 PMT. The spectral resolution for the steady measurements is about 0.05 nm in UV-Vis. For PL measurements at above room temperature, the sample was mounted in an Oxford OptistatDN2 nitrogen cryostat. The room temperature quantum efficiency (QE) of sample was measured using a barium sulfate coated integrating sphere attached to the FSP920, and glass matrix plate was used as the standard reference. The n-uv-cob LED modules consisted of a 6 8 array of n-uv (~385 nm) chips, and the working voltage and working current of this COB are 24 V and 120 ma, respectively. The EL spectrum was measured by FSP920 under an operating forward current. The phosphor-in-silicone (PiS) was prepared by initially dispersing the as-synthesized phosphors in silicone (C-5547:LSP-5547 = 1:10, Shin-Etsu) and then through two-step thermal curing the slurry process at 100 C for 1 h and then at 150 C for 2 h in an oven. For heat-resistance test, CGP:0.6%Eu 2+,2.0%Mn 2+ -PiG and CGP:0.6%Eu 2+,2.0%Mn 2+ -PiS samples were exposed at 200 C in the oven for the prescribed time period before the measurements of luminescent properties. For humidity-resistance test: CGP:0.6%Eu 2+,2.0%Mn 2+ -PiG sample was immersed into 85 C water for the prescribed time period, then the CGP:0.6%Eu 2+,2.0%Mn 2+ -PiG is dried at 200 C for 1 h before test the emission intensity. The thermal conductivity of host glass was measured using a Hot Disk TPS 2500 Thermal Constants Analyzer. Electroluminescence (EL) spectra were recorded using FSP920 Time Resolved and Steady State Fluorescence Spectrometers at a forward-current. S-3

4 Figure S1. XRD patterns of CGP, CGP:0.6%Eu 2+, CGP:1.0%Mn 2+, CGP:0.6%Eu 2+,yMn 2+ (y = 1.0, 2.0, 3.0, 4.0, 5.0, 7.0, 10.0%) phosphors and Ca 9 Y(PO 4 ) 7 standard pattern (JCPDS ). Note: A series of phosphors CGP:Eu 2+,Mn 2+ were synthesized by solid state reaction method. All the samples were confirmed using XRD, no impurity are observed as shown in Figure S1. S-4

5 Figure S2. Photographs of CGP:0.6%Eu 2+,yMn 2+ (y = 0, 1.0, 2.0, 3.0, 4.0, 5.0, 7.0, 10%) phosphors: (a) under fluorescent lamp and (b) under 365 UV lamp. Note: Figure S2 shows the photographs of CGP:0.6%Eu 2+,yMn 2+ phosphors (y = 0, 1.0, 2.0, 3.0, 4.0, 5.0, 7.0, 10%) under fluorescent lamp and 365 nm UV lamp. It could be found the hue can be tuned from cyan to white, and even to red under UV light excitation. S-5

6 Figure S3. PLE and PL of (a) CGP:0.6%Eu 2+, (b) CGP:0.6%Eu 2+,2.0%Mn 2+, and (c) CGP:0.6%Eu 2+,10%Mn 2+ phosphors. S-6

7 Figure S4. Absorbance spectrum (red line) of glass matrix and excitation spectrum (blue dash) of CGP:0.6%Eu 2+ phosphor; Inset shows the photograph of glass matrix (thickness = 0.24 mm). S-7

8 Figure S5. PL spectra of CGP:0.6%Eu 2+,yMn 2+ phosphors (y = 0 for A ; y = 2.0% for B ; y = 3.0% for C ; y = 5.0% for D ; y = 10% for E ). Table S1. Comparison of CIE Chromaticity Coordinates for PiG and Phosphor ( ) of CGP:0.6%Eu 2+,yMn 2+ Samples under 385 nm Excitation (y = 0 for A and A ; y = 2.0% for B and B ; y = 3.0% for C and C ; y = 5.0% for D and D ; y = 10% for E and E ) PiG Phosphor CIE coordinates CIE coordinates x y x y A A B B C C D D E E S-8

9 Figure S6. Decay curves of CGP:0.6%Eu 2+,yMn 2+ -PiG and CGP:0.6%Eu 2+,yMn 2+ powder samples (y = 0, 2.0, 3.0, 5.0%). Table S2. Lifetime and Energy Transfer Efficiency of PiG and Phosphor Samples as Function of the Content of Mn 2+ PiG (Phosphor) Lifetime (μs) η ET (%) CGP:0.6%Eu (1.057) / CGP:0.6%Eu 2+,2.0%Mn (0.912) (13.72) CGP:0.6%Eu 2+,3.0%Mn (0.902) (14.66) CGP:0.6%Eu 2+,5.0%Mn (0.828) (21.67) Note: The decay curve of the singly Eu 2+ -doped PiG and powder phosphor can be well fitted into a single-exponential function with a decay time of μs and μs, respectively. For Eu 2+ -Mn 2+ codoped samples, the decay curves deviate slightly from a single exponential rule, indicating the presence of a nonradiative process. The effective lifetime was calculated by the following equation 1-2 S-9

10 τ = 0 ti(t)dt I(t) dt 0 according to the formula, the effective lifetimes were determined and shown in Table S2. In addition, the energy transfer efficiencies from Eu 2+ to Mn 2+ in PiG and phosphor samples were calculated by the following formula according to Paulose et al. 3 η ET = 1 τ τ 0 where τ 0 is the lifetime of the sensitizer Eu 2+ of the sample in the absence of Mn 2+, and τ is the lifetime of Eu 2+ in presence of Mn 2+. As a consequence, the energy transfer efficiencies were calculated as a function of the content of Mn 2+ and are represented in Table S2. S-10

11 Figure S7. Normalized PL Spectra of CGP:0.6%Eu 2+ phosphor and CGP:0.6%Eu 2+ -PiG. S-11

12 Figure S8. Relative integrated intensity of PL after immerging the PiG in water (85 o C) for the prescribed time period. S-12

13 References 1). Guo, N.; Huang, Y.; Yang, M.; Song, Y.; Zheng, Y.; You, H. A Tunable Single-Component Warm White-Light Sr 3 Y(PO 4 ) 3 :Eu 2+,Mn 2+ Phosphor for White-Light Emitting Diodes. Phys. Chem. Chem. Phys. 2011, 13, ). Guo, C.; Jing, H.; Li, T. Green-Emitting Phosphor Na 2 Gd 2 B 2 O 7 :Ce 3+ -Tb 3+ for Near-UV LEDs. RSC. Advances 2012, 2, ). Paulose, P. I.; Jose, G.; Thomas, V.; Unnikrishnan, N. V.; Warrier, M. K. R. Sensitized Fluorescence of Ce 3+ /Mn 2+ system in phosphate glass. J. Phys. Chem. Solids 2003, 64, S-13