Doping of lead halides perovskites with rare-earth metals ions has become of significant current interest for possible applications in optoelectronics. In this research, we studied the material preparation and the visible to near IR optical properties of Dy3+ doped CsPbCl3. The crystal was synthesized from purified starting materials and melt-grown by vertical Bridgman technique. Visible emission studies under resonant-intra-4f excitation at ~450nm revealed bright yellow emission centered at 575nm arising from the 4F9/2 to 4H13/2 transition of Dy3+ ions. Additional emission bands arising from the 4F9/2 excited states were centered at 485nm, 664nm and 752nm. The decay time of the 4F9/2 level was non-exponential with an average lifetime of ~320 µs. Near-infrared emission studies were performed using a 808 nm diode lasers and revealed several IR bands located at 1.14 µm (6H7/2+6F9/2 ->6H15/2), 1.33 µm(6H9/2+6F11/2 ->6H15/2) , 1.55 µm (6F5/2 ->6H11/2), and ~1.7 µm (6H11/2 ->6H15/2) arising from lower excited states of Dy3+ ions. More details of the emission spectra and dynamics of Dy: CsPbCl3 as well as a comparison to Dy: KPbCl2 will be presented at the conference

1. “Visible and infrared emission properties of
melt-grown Dy doped CsPbCl3 crystals
S. Uba, A. Kabir, U. Hömmerich
Hampton University, Hampton, VA 23668
S. B. Trivedi
Brimrose Technology Corporation
APS March Meeting 2020

2. Outline
◌ Motivation
◌ Materials
◌ Absorption Studies and Judd-Ofelt Analysis
◌ Visible emission studies & “Yellow-Laser Potential”
◌ IR emission studies
◌ Summary

3. Motivation: Dy3+ in Halide Perovskites
Focus of this work: -> Dy3+
->“yellow light” at ~575 nm:
-> “yellow” solid-state laser gain media:
• industrial or military application
• medicine for ophthalmic diagnosis/treatment
• for research and technology as optical pump
for ytterbium clock
-> “yellow” phosphor:
• for white light LED’s
• Visible light bulbs
Research Goal: Increase functionality of halide perovskites &
related structures for photonic applications through metal doping.
APbX3 and related structure APb2X5
(-> A=Cs, K, Rb; X=Cl, Br)
Metal Dopant: TM: Transition Metals
RE: Rare Earth

4. Material Processing & Crystal Growth
- CsPbCl3 synthesis: stoichiometric amounts of high purity (5N) CsCl and PbCl2.
- 2 wt.% DyCl3 was added for doping (under argon glove box)
- Loaded growth ampoules were sealed under vacuum (10-6 torr)
- Material was synthesized at ~50º C above its melting point of CPC ~600ºC.
- Two-zone furnace was employed for Bridgman crystal growth
- For comparison: Dy: KPb2Cl5 was prepared with a similar procedure
• Synthesized material: CsPbCl3
• Synthesized material: Dy: CsPbCl3
Bridgman growth:
• 2 zone furnace
• Growth rate: ~1-2mm/hr
• Gradient at solid/liquid interface: ~9C/cm

5. Crystal Growth Results & Transmission
• Dy: CsPbCl3
500 1000 1500 2000 2500 3000 3500
0
10
20
30
40
50
60
Transmission(%)
Wavelength (nm)
Dy: CsPbCl3
1000 2000 3000 4000 5000 6000
0
10
20
30
40
50
60
70
Transmission
Wavelength (nm)
CsPbCl3
OH
• Undoped CsPbCl3 • For comparison: Dy: KPb2Cl5
Issues: material cracking and dopant segregation

6. Absorption Spectroscopy: JO analysis-Dy: CPC
Transition
6
H15/2 
Average
Wavelength
(µm)
  () d
(µm/cm)
Sed
(experimental)
(x 10-20
cm2
)
(Sed
(calculated)
(x 10-20
cm2
)
6
H11/2 1.7 0.0071 4.02 5.21
6
H9/2+6
F11/2 1.3 0.0497 3.72 3.73
6
H7/2+6
F9/2 1.1 0.0030 2.91 3.12
6
F7/2 0.91 0.0032 3.56 2.81
6
F5/2 0.81 0.0019 1.42 2.36
500 1000 1500 2000 2500 3000
0.5
1.0
1.5
2.0
2.5
3.0
6
F7/2
6
F5/2
6
H7/2
+6
F9/2
6
H9/2
+6
F11/2
6
H11/2
6
H13/2
AbsorptionCoefficient(cm-1
)
Wavelength (nm)
Dy: CsPbCl3
6
H15/2
->
Dy: CsPbCl3
2=4.05x10-20 cm2
4=0.06x10-20 cm2
6=0.39x10-20 cm2
• Experimental line strengths:
• Judd-Ofelt calculated line strengths:
• Note: 6H13/2 was not included due to overlap with OH absorption
0
5
10
15
20
6
H15/2
4
F9/2
G11/2
4
I15/2
6
F3/2
6
F5/2
6
F7/2
6
H7/2+6
F9/2
6
H9/2+6
F11/2
6
H11/2
6
H13/2
~810nm
~911nm
~1115nm
~1300nm
~1705nm
x103
(cm-1
)
~2870nm
• U -> reduced matrix elements from literature
• : -> Judd-Ofelt Intensity fitting parameters:
with n=1.75

7. Visible Emission & Excitation Spectra: Dy: CPC
Pumping schemes:
-> above-gap:
weak yellow emission
-> intra-4f from
strong emission
~ 454 nm (4I15/2)
~ 475nm (4F9/2)
Visible emission from
4F9/2 excited state:
~ 479 nm (6H15/2)
~ 575 nm (6H13/2)
~ 664 nm (6H11/2)
~ 753 nm (6H9/2)
Yellow-Branching ratio:
0.52
0
5
10
15
20
25
30
Energy(103
cm-1
)
6
H15/2
6
H13/2
6
H11/2
6
H9/2
+6
F11/2
6
H7/2
+6
F9/2
6
H5/2
6
F7/2
6
F5/2
6
F3/2
4
F9/2
4
I15/2
4
G11/2
4
F7/2
~454nm
~475nm
~575nm
300 350 400 450 500
0.0
0.5
1.0
4
F9/2
6
H15/2
->
Intensity(a.u)
Wavelength (nm)
4
I15/2
CPC:
Eg~3.0eV
Excitation: Dy: CPC
mon: 575nm
Eg~3eV
400 500 600 700 800
0.0
0.5
1.0
Intensity(a.u)
Wavelength (nm)
6
H15/2
6
H13/2
6
H11/2
6
H9/2
Emission Dy:CPC
Pump:455nm
4F9/2
0
5
10
15
20
25
Energy(103
cm-1
)
6
H15/2
6
H13/2
6
H11/2
6
H9/2+6
F11/2
6
H7/2+6
F9/2
6
H5/2
6
F7/2
6
F5/2
6
F3/2
4
F9/2
4
I15/2
4
G11/2
~455nm
~485nm
~575nm
~664nm
~753nm

8. Visible Emission & Excitation Spectra: Dy: KPC
Visible emission from
excited state 4F9/2
~ 479 nm (6H15/2)
~ 575 nm (6H13/2)
~ 664 nm (6H11/2)
~ 753 nm (6H9/2)
Yellow branching
ratio: ~0.66
Pumping schemes:
-> above gap
weak yellow emission
-> intra 4f
strong emission
~ 390 nm (4F7/2)
~ 428 nm (4G11/2)
~ 454 nm (4I15/2)
~ 475 nm (4F9/2)
300 350 400 450 500
0.0
0.5
1.0
Excitation: Dy: KPC
mon: 575nm
6
H15/2
->
Intensity(a.u)
Wavelength (nm)
4
I15/2
4
G11/2
4
F7/2
4
F9/2
KPC
Eg~3.8eV
0
5
10
15
20
25
30
~428nm
Energy(103
cm-1
)
6
H15/2
6
H13/2
6
H11/2
6
H9/2
+6
F11/2
6
H7/2
+6
F9/2
6
H5/2
6
F7/2
6
F5/2
6
F3/2
4
F9/2
4
I15/2
4
G11/2
4
F7/2
~390nm
~454nm
~475nm
~575nm
Eg~3.8eV
400 500 600 700 800
0.0
0.5
1.0
Emission Dy:KPC
Pump:455nm
Intensity(a.u)
Wavelength (nm)
6
H15/2
6
H13/2
6
H11/2
6
H9/2
4F9/2->
0
5
10
15
20
25
Energy(103
cm-1
)
6
H15/2
6
H13/2
6
H11/2
6
H9/2+6
F11/2
6
H7/2+6
F9/2
6
H5/2
6
F7/2
6
F5/2
6
F3/2
4
F9/2
4
I15/2
4
G11/2
~455nm
~485nm
~575nm
~664nm
~753nm

9. JO-analysis: Decay Rates & Branching Ratios
Radiative Parameters Dy:CPC 4F9/2
6H13/2 Dy:KPC 4F9/2
6H13/2
λp (nm) (Center Peak) 577 574
Δλeff (nm) (FWHM) 9.47 9.09
AR (s-1) 434.5 1402
βR (Cal) 0.73 0.64
βR (Exp) 0.52 0.66
σe (x 10-22 cm2) 21.9 56.1
τR (x 10-3 s) 1.70 0.46
σe x τR (x 10-25 cm2) 37.3 25.9
The Judd-Ofelt intensity fitting parameters (λ) for KPb2Cl5 and reduced matrix elements (U )
for Dy3+ is obtained from literatures
2=4.05x10-20 cm2 , 4=0.06x10-20 cm2 , 6=0.39x10-20 cm2
 To calculate the radiative parameters for KPb2Cl5: Dy3+ , crystal refractive index n=2
• Transition Probability (AR)
• Total Transmission Rate (AT)
• Decay Rate (𝝉 𝑹)
• Branching Ratio (𝜷 𝑹)

10. Lifetime & Emission Cross-Section Spectra
Dy: CPC;  ~1ms
(low concentration <0.5wt%)
Dy: KPC; ~0.36ms
σ-product: 3.7x10-24cm2
2
0
2
8
p
radn c
 

  

 %
Fuchtbauer
Ladenburg:
0 1000 2000 3000 4000 5000 6000 7000
0.001
0.01
0.1
1
slow component
Dy3+ intra-4f emission
Intensity(a.u)
Time (ms)
fast component
yellow background emission
monitor wavelength:
575nm
low conc sample
<0.5wt%
0 1000 2000
0.001
0.01
0.1
1
300K: average lifetime: 363us
Intensity(a.u)
Time (ms)
Dy: KPC
300K
σ-product: 2.6 x10-24cm2
550 560 570 580 590 600
0
1
2
EmissionCross-section(x10-21
cm2
)
Wavelength (nm)
576.6nm
550 560 570 580 590
0
2
4
6
EmissionCross-Section(x10-21
cm2
)
Wavelength (nm)
Dy:KPC
574.1nm
1
thP

:
σp=2.1x10-20cm2
σp=5.6x10-20cm2

11. Laser Potential & Comparison
Crystals λp
(nm)
βR σe (x 10-22
cm2)
τR (Cal) τR (Exp) σe x τR (x 10-24
cm2)
η (%)
Dy:KPC 575 0.64 56.1 0.46 ms 0.36 ms 2.6 78.2
Dy:CPC 577 0.52 21.9 1.70 ms 1.0 ms 3.7 58.8
Dy:KGF 577 0.53 13.6 1.68 ms 1.04 ms 2.2 61.9
Dy:NGM 573 0.75 0.01 255.7 µs 125 µs 2.8 48.9
Dy:YAG 582.7 0.59 0.003 2.020 ms 376 µs 6.1 18.6
In comparison to other Dysprosium doped crystal explored for 575 nm lasing
application,
• Dy:CPC and Dy: KPC show high branching ratios, quantum efficiencies,
emission cross-sections, and σ-products, which are comparable or better
that reported for other Dysprosium doped crystals.
• Dy:KPC and Dy:CPC are promising candidates for yellow laser applications.
Crystal growth process and sample quality have to be improved.

12. Initial IR emission data
Emitted peaks in Near
IR window
~ 1.1 µm (6H7/2 + 6F9/2)
~ 1.3 µm (6F11/2 + 6H9/2)
Emitted peaks in Near
IR window
~ 1.1 µm (6H7/2 + 6F9/2)
~ 1.3 µm (6F11/2 + 6H9/2)
~ 1.5 µm (6H11/2)
• Dy: CPC and Dy: KPC emission spectrum shows peaks in the 1.1µm, 1.3µm and 1.5µm.
• Both crystals are candidates for optical amplifiers/lasers operating at the Near-IR
communication windows (1.3 & 1.5 µm)
0
2
4
6
8
10
12
1.7mm
1.5mm
1.3mm
6
H5/2
6
F5/2
6
F7/2
6
H7/2+6
F9/2
6
H9/2+6
F11/2
6
H11/2
6
H13/2
6
H15/2
Energy(103
cm-1
)
1.1mm
0
2
4
6
8
10
12
1.7mm
1.5mm
1.3mm
6
H5/2
6
F5/2
6
F7/2
6
H7/2+6
F9/2
6
H9/2+6
F11/2
6
H11/2
6
H13/2
6
H15/2
Energy(103
cm-1
)
1.1mm
1000 1200 1400 1600
0.00
0.01
0.02
0.03
1.5 mm
1.3 mm
Intensity(a.u)
Wavelength (nm)
6
F9/2
+ 6
H7/2
-> 6
H15/2
6
F5/2
->6
H11/2
6
F11/2
+ 6
H9/2
-> 6
H15/2
Dy:KPC
1000 1200 1400 1600
0.000
0.002
0.004
0.006
1.5 mm
6
F5/2
->6
H11/2
6
F11/2
+ 6
H9/2
-> 6
H15/2
6
F9/2
+ 6
H7/2
-> 6
H15/2
Intensity(a.u)
laser
2n order
Dy:CPC
1.3 mm

13. Summary & Conclusion
• Dy:CPC was synthesized using high purity (5N) CsCl and PbCl2, 2 wt.%
DyCl3 was added for doping (under argon glove box) and Dy:KPC was
synthesized under the same conditions for comparison.
• Dy: CPC and Dy: KPC exhibited bright “yellow” emission under direct
intra4f pumping at ~455nm. Absorption, visible emission/excitation, near IR-
emission were conducted and a Judd-Ofelt analysis was performed to
determine radiative decay rates and branching ratios for both crystals.
• Dy: CPC and Dy: KPC exhibit large emission cross-sections, σeτR values, and
high quantum efficiencies making them viable candidates as gain medium for
the 575 nm “yellow” lasers. Both crystals also revealed near-IR emissions
which are currently being explored for laser applications.
• Preparation of Dy3+ doped CPC perovskites nanoparticles is underway for
possible light source applications in optoelectronic devices.
Acknowledgement:
• NSF PREM support through NSF grant 827820 (Hampton-Brandeis PREM) and
ARO grant W911NF1810447.