The document explores organometallic halide perovskites used in electroluminescent diodes, discussing their structural and optical properties, and production techniques. It highlights their advantages such as tunable bandgap, high optical absorption, and application in photovoltaics, while cautioning about stability and toxicity issues. Key characterization methods like X-ray diffraction and electronic spectroscopy are presented to analyze material properties and behaviors.

1. Near Infrared to Visible Electroluminescent
Diodes Based on Organometallic Halide
Perovskites: Structural and Optical
Investigation
• Submitted by: Preeti Choudhary
• Roll No.= 17/MAP/016
• MSC(applied physics)

2. content
• overview of perovskites
• classification of Perovskites
• Production of Perovskites
• Perovskites bandgap
•Characterization: XRD, UV-VIS
spectroscopy
• material properties

3. Electroluminescence(EL)
Electroluminescent(El) panel is a flat light bulb sandwich
consisting of layers of conductive and non-conductive plastic
and a layer of phosphor.
The phosphor is laminated between two conductive layers. As
a voltage is applied between the two conductive layers, or
electrodes, the electrical current passes through the panel
allows the phosphor crytals rapidly charged and emitted light
energy which illuminates the printed overlay.

4. Origin And History of Perovskite
compounds
• Perovskite is calcium titanium oxide or calcium
titanate, with the chemical formula CaTiO3.
• Very stable structure, large number of compounds,
variety of properties, many practical applications.
• Key role of the BO6 octahedra in ferromagnetism and
ferroelectricity.
• Extensive formation of solid solutions
• material optimization by composition control and
phase transition engineering.

5. Perovskite
Orthorhombic perovskite ABO3

6. Classification of Perovskite System

7. Production of Perovskite cell

8. The Perovskite Bandgap can be tuned
by Chemical Substitution
• The band gap can be tuned from 1.57 eV to 2.23 eV
by substituting bromine for iodine in CH3NH3Pb(Brx
I1-x )3

9. Perovskite

10. Typical crystal structure of organometallic halide (ABX3) where A is for Alkylamine
(R-NH3), B is for divalent metal (Pb+2) and X is for halide ion (X-).
• Organometal halides (CH3NH3PbX3 = ABX3, where
A = CH3NH3+, B = divalent metal, i.e., Pb+2 and X- =
halide ion) based perovskite semiconductors have
shown excellent performance in solar cells3,4,5,6
application and optical gain.

11. XRD
• Solid materials are formed by atoms or atomic group
arranged in certain way. When an x-ray beam is injected
into the material . it would be scattered by atoms.
• If two or more x-ray beams scattered by the atoms that
have some phase differences are superimposed onto
each other, diffraction is occurred. The x-ray diffraction
instrument is used to collect the intensities of the
scattered signals to get the diffraction pattern of the
measured sample.
• This pattern is normally as the signal intensity versus
the phase angle. An advantage for using X- ray
diffraction measurement is that it can analyse the
material without causing damage on the material.

12. XRD
• The crystallite size of Titanium dioxide nanoparticles
evaluated using the Debye-Scherer formula.
• D=kλ/βcosθ
• Where k is the constant (0.9), λ is the x-ray wave length of
X-ray , β is the full width half maximum (FWHM) of the
peak and Ѳ is the reflection angle.

13. Bragg’s Law and X-ray Diffraction
How waves reveal the atomic structure of crystals
nl = 2dsin()
Atomic
plane
d=3 Å
l=3Å
=30o
n-integer
X-ray1
X-ray2
l
2-diffraction angle
Diffraction occurs only when Bragg’s Law is satisfied
Condition for constructive interference (X-rays 1 & 2) from planes with
spacing d

14. XRD pattern for annealed film of four perovskites materials
with a change of halide component in ABX3 configuration on
glass substrate.

15. Electronic Spectroscopy
• This is the earliest method of molecular
spectroscopy.
• A phenomenon of interaction of molecules with
ultraviolet and visible lights.
• Absorption of photon results in electronic
transition of a molecule, and electrons are
promoted from ground state to higher electronic
states.

16. Lambert-Beer’s Law
A=ebc
e: the molar absorptivity (L mol-1 cm-1)
b: the path length of the sample
c :the concentration of the compound in
solution, expressed in mol L-1
The Lambert -Beer law states that when a
monochromatic beam of light passes through a
dilute solution, then the light absorbed is directly
proportional to the concentration of the substance
and the path length of the light through the
solution

17. Optical properties of perovskites. (a) UV-Vis absorbance spectra on energy scale for all four perovskite.
(b) Photoluminescence spectra of perovskite semiconductor film prepared on quartz substrates with
excitation wavelength corresponds to their UV-Vis spectra. (c) Quenching of PL at
different interlayer for ABI3-xClx on quartz substrates with excitation wavelength of 650 nm.

18. Material Properties
Good for photovoltaics but with caution.
• cheap manufacturing:
lower manufacturing costs expected: directly deposited from solution.
Caution: Encapsulation needed,which may increase.
• Material Properties for high efficiency photovoltaics:
1. High optical absorption coefficient
2. Excellent charge carrier transport(crystallinity,diffusion,length,carrier mobility)
3. Promising device parameter: high Voc of >1.1v is reported
• Stability:
study shows it can maintain more than 80% of initial efficiency
after 500 hours.
cation:
toxicity from pd
scaling problem

19. Importance of Perovskite Material
• Advantage
direct optical band gap of around 1.5ev.
long diffusion length
long minority carrier lifetimes
Broad absorption range from visible to near-
infrared spectrum(800nm)
• Disadvantage
Degradation of methyl ammonium lead iodide
perovskite

20. Thank you