Energy transfer efficiency - Società Italiana di Fisica

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CHARACTERIZATION and DEVELOPMENT of MATERIALS
for PHOTONICS and OPTOELECTRONICS
CNR - Istituto di
Fotonica e
Nanotecnologie
CSMFO Lab.
www.science.unitn.it/~gcsmfo/
CNR-IFAC Istituto di Fisica
Applicata, “Nello Carrara”
Vetri attivati con ioni di terre rare per conversione in
frequenza della radiazione solare.
Davor Ristić 1, Guillaume Alombert Goget2, Belto Dieudonne3, Enrico Moser4,
Stefano Varas1, Simone Berneschi5,6, Stefano Pelli6, Brigitte Boulard3,
Maurizio Ferrari1
IFN – CNR CSMFO Lab., Via alla Cascata 56/C Povo, 38123 Trento, Italy.
2 Université de Versailles, Lab. LISV, 78140 Vélizy Villacoublay, France.
3 Lab. LdOF, UMR CNRS 6010, Université du Maine, 72085 Le Mans, France.
4 Dipartimento di Fisica, Università di Trento, Povo, 38123 Trento, Italy.
5 Museo Storico della Fisica e Centro “Enrico Fermi”, 00184 Roma, Italy.
6 IFAC - CNR, MDF Lab., 50019 Sesto Fiorentino, Italy
1
Società Italiana di Fisica, XCVII Congresso Nazionale, L’Aquila, 26 - 30 Settembre, 2011 [ Sezione 5 Fisica Applicata]
OUTLINE
 Motivation
 Tb3+ and Yb3+ ions in sol-gel derived SiO2HfO2 glass ceramic planar waveguides
 Pr3+ and Yb3+ ions in fluoride glasses ZLAG
 Perspectives
MOTIVATION
Silicon Photovoltaic devices are able to convert only a
portion of solar spectrum.
Photonflux (1018 / m2 s nm)
5
Double silicon band gap
Silicon band gap
4
3
Up conversion
Down conversion
2
1
0
500
1000
1500
2000
2500
Wavelength [nm]
3000
3500
4000
GLASS CERAMICS
 combine the advantages of glasses and crystals
Better spectroscopic properties then glasses (higher absorption and
emission cross-section, reduction of the non-radiative relaxation
thanks to the lower phonon cut-off energy)
Transparency
Alessandro Chiasera, Guillaume Alombert-Goget, Maurizio Ferrari, Simone Berneschi, Stefano Pelli, Brigitte Boulard, and
Claire Duverger Arfuso, “Rare earth activated glass-ceramic in planar format”, Optical Engineering 50 (2011) pp. 071105-1/10
Down conversion in glass based materials
Since the down conversion effect was observed in 2001 in oxyfluoroborate glass
doped Gd3+ [1], few studies have been published on the down conversion in
glasses. It’s probably because some author says that host materials should be
highly crystalline to minimize energy transfer to host lattice luminescent defects
[2].
POWDERS, GLASSES and GLASS CERAMICS
Thus, studies on down conversion have been preferred in glass ceramic to
combine mechanical aspects of the crystal and the advantage of the glass.
Material
Doping contents
[mol%]
Estimated effective
quantum efficiency
Reference
45SiO2-12Na2O-23Al2O3-20LaF3
0.5Tm3+-8 Yb3+
162%
[3]
50SiO2–20Al2O3–20LiF–10GdF3
0.5Tm3+-30 Yb3+
187%
[4]
60SiO2-20 BaF2-20ZnF2
LaBGeO5
44SiO2-28Al2O3-17NaF-11YF3
1.0Tb3+-10 Yb3+
0.1Tb3+-0.5 Yb3+
0.1 Pr3+-1.5 Yb3+
145%
146%
194%
[5]
[6]
[7]
[1] A. Kumar, D.K. Rai, S.B. Rai, Solid State Communications 117 (2001) 387-392.
[2] B.S Richards, Solar Energy Material & Solar Cells 90 (2006) 1189-1207.
[3] S. Ye, B. Zhu, J. Luo, J. Chen, G. Lakshminarayana, J. Qiu, Optics Letters 16 (2008) 8989.
[4] G. Lakshminarayana, H. Yang, S.Ye, Y. Liu, J. Qiu, J. Phys. D: Appl. Phys. 41 (2008) 175111.
[5] J.X. Chen, S. Ye, X. Wang, J. R. Qiu, Chin. Phys. Lett. 25, (2008) 2078.
[6] X. Liu, S. Ye, Y. Qiao, G. Dong, B. Zhu, D. Chen, G. Lakshminarayana, J. Qiu, Appl Phys B (2009) 96: 51–55.
[7] D. Chen, Y. Wang, Y. Yu, P. Huang, F. Weng, Optics Letters 33 (2008) 1884.
Tb3+ and Yb3+ ions in sol-gel derived
SiO2-HfO2 glass ceramic planar
waveguides
Down conversion with Tb3+/ Yb3+
One blue photon @ 488nm
Two infrared photon @ 980 nm
TEOS + EtOH
H2O + HCl
refluxed
1 h, 65 °C
Pre-hydrolized TEOS solution
HfOCl2 • 8H2O + EtOH
70 SiO2 – 30 HfO2
Flowchart of the
synthesize protocol
Tb(NO3)3 5H2O
and
Yb(NO3)3 5H2O
Aging 16 h at R.T.
dip-coating
50’’ at 900 °C after each dip.
A heat treatment of 900 °C for 5
min after 30 dips. An additional
heat treatment was performed of
1000 °C for 30 min in order to
nucleate nanocrystals
Samples
Rare earth concentration, refractive index and layer thickness of the samples.
Sample label
Terbium
concentration in
mol%
Ytterbium
concentration
in mol%
[email protected] nm
TE
polarization
[± 0.001]
[email protected] nm
TE polarization
[± 0.001]
Layer
thickness
[±0.2µm]
AR1
0.5
0
1.621
1.616
1.0
A1
0.5
1
1.626
1.621
1.0
A2
0.5
2
1.631
1.626
1.0
A3
0.5
3
1.633
1.628
1.1
BR1
0.2
0
1.623
1.617
1.1
B1
0.2
0.8
1.604
1.608
0.9
BR3
0.6
0
1.624
1.620
1.1
B3
0.6
2.4
1.630
1.625
1.2
BR5
1
0
1.626
1.621
1.2
B5
1
4
1.638
1.633
1.1
Room temperature photoluminescence spectra of the 2F5/22F7/2 transition of
Yb3+ ions after excitation at 476 nm for the three samples of the first series.
Each spectrum was normalized to the maximum of the luminescence
intensity.
The emission of the Yb3+ ion after excitation at 476 nm is a indication of the
presence of an efficient energy transfer from Tb3+ to Yb3+.
A3
A2
A1
960
980
1000
1020
Wavelength [nm]
1040
1060
Intensity [ a.u. ]
Intensity [arb.units]
However, it is not possible to evaluate the conversion efficiency only on the
base of the photoluminescence spectra.
B5
B3
B1
960
980
1000
1020
1040
wavelength [nm]
1060
Energy transfer efficiency
between Tb3+ and Yb3+ :
Tb Yb
I

1
I
Tb Yb
dt
Tb dt
Intensity [arb. units]
Decay curves analysis
The relation between the transfer
efficiency and the effective quantum
efficiency is linear and is defined as:
ηEQE = ηTb-r(1-ηTb-Yb)+2ηTb-Yb
where the quantum efficiency for Tb3+
ions, ηTb-r, is set equal to 1.
1
0,1
AR1
A1
A2
A3
0,01
0
2
4
6
8
10
12
14
Time [ms]
Decay curves of the luminescence from
the 5D4 metastable state of Tb3+ ions for
the first samples series under excitation
at 355 nm.
Transfer efficiency and effective quantum efficiency as a function of Yb3+ molar
concentration for A samples where Tb3+ content is fixed at 0.5 mol%
Composition (Yb concentration in mol%)
1%
2%
3%
Estimated transfer efficiency (in glass ceramic)
14%
24%
25%
Estimated effective quantum efficiency (in glass 114%
ceramic)
Estimated transfer efficiency (in glass)
2%
124%
125%
4%
6%
Estimated effective quantum efficiency (in glass)
104%
106%
102%
For compositions with Tb3+ content kept constant at 0.5 mol% and increasing
Yb3+ molar concentration, we observed that:
• the Tb-Yb energy transfer efficiency increases with the increase of the
molar ratio Yb/Tb;
• the energy transfer efficiency does not exceed 24-25%.
RB1
B1
0
2
4
6
8
10
12
14
Time [ms]
Intensity [a.u.]
Intensity [a.u.]
Intensity [a.u.]
Decay curves of the luminescence from the 5D4 metastable state of Tb3+ ions for
the B samples series upon excitation at 355 nm.
RB3
B3
0
2
4
6
8
10
12
RB5
B5
0
14
2
4
6
8
10
12
Time [ms]
Time [ms]
Transfer efficiency and effective quantum efficiency as function of (Yb3++Tb3+)
molar concentration for B samples with constant molar ratio Yb/Tb=4
Composition (Tb+Yb concentration in mol %)
1%
3%
5%
Transfer efficiency
1%
18%
38%
Effective quantum efficiency
101% 118% 138%
This result could be compare with the transfer efficiency equal to 33% obtain in
60SiO2-20 BaF2-20ZnF2 glass doped with 1 mol % of Tb3+ and 5 mol % of Yb3+[1].
[1] J.X. Chen, S. Ye, X. Wang, J. R. Qiu, Chin. Phys. Lett. 25, (2008) 2078.
14
CHARACTERIZATION and DEVELOPMENT of MATERIALS for
PHOTONICS and OPTOELECTRONICS Research Group
Pr3+ and Yb3+ ions in fluoride glasses
ZLAG
70ZrF4 23.5LaF3 0.5AlF3 6GaF3
Down conversion with Pr3+/ Yb3+
One Blue photon @ 476nm
Two infrared photon @ 980 nm
Fluoride glass ZLAG
 Heavy metal fluoride glasses (HMFGs) present:
- Low phonon energy (~600 cm-1);
- High doping possibility for rare-earth ions;
 The only fluoride glass to achieve glass ceramics (GCs) is the composition named
ZLAG (70ZrF4 23.5LaF3 0.5AlF3 6GaF3 in mol%) :
-These glasses and GCs, doped with RE = Er3+, Yb3+, Pr3+ have been successfully
obtained as thin films, using Physical Vapor Deposition [1].
For these reasons the fluoride glass ZLAG seems a suitable matrix to produce
RE activated films for down-conversion process.
[1] O. Péron, B. Boulard, Y. Jestin, M. Ferrari, C. Duverger-Arfuso, S. Kodjikian, Y. Gao, J. Non-Cryst. Solids 354, (2008) 3586.
Samples properties
rare earth content, thermal characteristics and thickness:
Samples
Labels
YbF3
(mol%)
Temperatures
of vitreous
transition
Tg (°C)
Temperatures
of
crystallization
Tc (°C)
stability
criteria
T(°C)
T
(mm)
ZLAG 0.5Pr3+ - xYbF3
BV0
BV1
BV2
BV3
BV5
0
1
2
3
5
404
404
403
407
410
472
474
476
482
476
68
70
73
75
66
4.6
3.5
3.6
3.2
3.5
0.9ZLAG+ 0.1ZBLA
0.5Pr3+ xYbF3
BV10
10
377
423
46
1.7
addition of BaF2 is necessary to allow higher Yb3+ content
Room temperature photoluminescence spectra of the 2F5/2  2F7/2
transition of Yb3+ ions after excitation at 476 nm for the samples with
Ytterbium
The presence of the Yb3+ ion emission after excitation in the blue region is an
evidence of an efficient energy transfer from Pr3+ to Yb3+.
2
2
F5/2 F7/2
BV10
BV5
BV3
BV2
BV1
900
1000
1100
wavelength [nm]
Decay curves analysis
Energy transfer efficiency between the 3P0
state of the Pr3+ and 2F5/2 state of Yb3+ :
 Pr Yb
I

 1
I
Pr Yb
Pr
dt
ex= 440 nm
em= 478 nm
Decay curves of the luminescence from the
3P metastable state of Pr3+ ions at 478 nm
0
under excitation at 440 nm in function of
the Yb3+ concentration
BV0
BV1
BV2
BV3
BV5
BV10
dt
0
50
100
150
200
Time [µs]
Evaluated energy transfer efficiency as a function of Yb3+
molar concentration
Samples Labels
YbF3 (mol%)
BV0
BV1
BV2
BV3
BV5
BV10
0
1
2
3
5
10
Transfer
efficiency (%)
38
55
70
82
92
The energy transfer efficiency (92%) observe for the highest concentration of ytterbium is
almost equal to the one obtained in K3YF10 crystal with the same doping (91% [1]) and
higher that the one obtained in oxyfluoride germanate glass (73.6-79.3% for 8-12% Yb3+
[2]).
[1] D. Serrano, A. Braud, J.-L. Doualan, P. Camy, A. Benayad, V. Ménard, R. Moncorgé, Optical Material, (2010).
doi:10.1016/j.optmat.2010.07.023.
[2] G. Lakshminarayana, Jianrong Qiu, Journal of Alloys and Compounds 481, 582–589 (2009).
Consolidated results
 Efficient Tb3+: Yb3+ co-doped 70 SiO2 - 30 HfO2 glass ceramic
down-conversion waveguides and down-conversion bulks Pr3+-Yb3+
co-doped ZLAG glasses have been developed.
 Emission of the ytterbium at 980 nm was observed in both cases
 We evaluated the energy transfer efficiency for the 3P0 state of the
Pr3+ and the 5D4 state of Tb3+ to the Yb3+ ions for the first step of the
quantum cutting process.
The highest transfer efficiency, equal to 38%, has been achieved so
far in 70 SiO2 - 30 HfO2 glass ceramic films activated by 1% of
terbium and 4% of ytterbium.
 The sample with 0.5 mol% of praseodymium and 10 mol% of
ytterbium presents an energy transfer efficiency of 92%, similar to
the best results obtained in fluoride crystals with the same doping.
Perspectives
 Glass and glass-ceramic waveguides
 Optimization of concentration
 Integration (Light
concentrators)
confinement
and
CNR - Istituto di
Fotonica e
Nanotecnologie
CHARACTERIZATION and DEVELOPMENT of
MATERIALS for PHOTONICS and
OPTOELECTRONICS Laboratory
CSMFO Lab.
www.science.unitn.it/~gcsmfo/
ACKNOWLEDGEMENTS:
 COST action MP0702 (2008-2011)
 CNES project (2009-2010) (2011-2013)
 Oxi-Solar project (2010-2011)
NSBMO research project (2010-2013)
CNR-IFAC Istituto di Fisica
Applicata, “Nello Carrara”,

Energy transfer efficiency - Società Italiana di Fisica

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