Perovskite

Perovskite: introduction, classification, structure of perovskite, method to synthesis, characterization by XRD and UV- vis spectroscopy , lambert beer's law, material properties and advantage and application.

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 ABO 3

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=k λ / β cos θ 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 n l = 2dsin(  ) Atomic plane d=3 Å  =3 Å  =30 o 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= e bc 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 : High optical absorption coefficient Excellent charge carrier transport( crystallinity,diffusion,length,carrier mobility) 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

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