scholarly journals A2AgCrBr6 (A = K, Rb, Cs) and Cs2AgCrX6(X = Cl, I) Double Perovskites: A Transition-Metal-Based Semiconducting Material Series with Remarkable Optics

Nanomaterials ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 973 ◽  
Author(s):  
Pradeep R. Varadwaj
Keyword(s):  
Transition Metal ◽  
Optical Absorption ◽  
Absorption Coefficient ◽  
Dielectric Function ◽  
Density Of States ◽  
Dielectric Constants ◽  
Double Perovskites ◽  
Absorption Coefficients ◽  
Band Structures ◽  
Effective Masses

With an interest to quest for transition metal-based halogenated double perovskites AB′B″X6 as high performance semiconducting materials for optoelectronics, this study theoretically examined the electronic structures, stability, electronic (density of states and band structures), transport (effective masses of charge carriers), and optical properties (dielectric function and absorption coefficients, etc.) of the series A2AgCrBr6 (A = K, Rb, Cs) using SCAN + rVV10. Our results showed that A2AgCrBr6 (A = Rb, Cs), but not K2AgCrBr6, has a stable perovskite structure, which was revealed using various traditionally recommended geometry-based indices. Despite this reservation, all the three systems were shown to have similar band structures, density of states, and carrier effective masses of conducting holes and electrons, as well as the nature of the real and imaginary parts of their dielectric function, absorption coefficient, refractive index, and photoconductivity spectra. The small changes observed in any specific property of the series A2AgCrBr6 were due to the changes in the lattice properties driven by alkali substitution at the A site. A comparison with the corresponding properties of Cs2AgCrX6 (X = Cl, I) suggested that halogen substitution at the X-site can not only significantly shift the position of the onset of optical absorption found of the dielectric function, absorption coefficient and refractive spectra of Cs2AgCrCl6 and Cs2AgCrI6 toward the high- and low-energy infrared regions, respectively; but that it is also responsible in modifying their stability, electronic, transport, and optical absorption preferences. The large value of the high frequency dielectric constants—together with the appreciable magnitude of absorption coefficients and refractive indices, small values of effective masses of conducting electrons and holes, and the indirect nature of the bandgap transitions, among others—suggested that cubic A2AgCrBr6 (A = Rb, Cs) and Cs2AgCrCl6 may likely be a set of optoelectronic materials for subsequent experimental characterizations.

Mathematical modeling determination coefficient of magneto-optical absorption in semiconductors in presence of external pressure and temperature

2021 ◽  
pp. 2150293
Author(s):  
U. I. Erkaboev ◽  
R. G. Rakhimov ◽  
N. A. Sayidov
Keyword(s):  
Mathematical Modeling ◽  
Experimental Data ◽  
Optical Absorption ◽  
Absorption Coefficient ◽  
Density Of States ◽  
External Pressure ◽  
Optical Absorption Coefficient ◽  
Dispersion Law ◽  
Different Temperatures ◽  
Simulation Results

The calculation of the coefficients of magneto-optical absorption in semiconductors at different temperatures and pressures is carried out. A formula for the temperature dependence of the oscillations of the combined density of states by the Kane dispersion law is obtained. Mathematical modeling has been carried out that determines the magneto-optical absorption coefficient in semiconductors in the presence of external influences. A new method for determining the magneto-optical absorption coefficient in semiconductors in the presence of pressure and temperature is proposed. The correspondence of simulation results with experimental data is shown.

Nonlinear Intersubband Optical Absorption Coefficient and Refractive Index Changes in Asymmetric Parabolic Double Quantum Wells

2017 ◽  
Vol 6 (1) ◽  
pp. 121-125 ◽  
Author(s):  
Menberu Mengesha Woldemariam
Keyword(s):  
Refractive Index ◽  
Optical Absorption ◽  
Absorption Coefficient ◽  
Quantum Wells ◽  
Optical Absorption Coefficient ◽  
Double Quantum ◽  
Absorption Coefficients ◽  
Total Change ◽  
Left Handed ◽  
Index Changes

The change in optical absorption coefficients and refractive index in GaAs-AlGaAs asymmetric parabolic double quantum wells (DQWs) with applied electric field are studied in detail. Analytical expressions for the linear, nonlinear and total intersubband absorption coefficient and refractive index changes are obtained by using compact density matrix approach. It is found that the magnitude of the nonlinear part of the change in refractive index and absorption coefficients are larger than the linear part in the given frequency region. The value of the total change in refractive index is negative and the asymmetric DQWs becomes left handed media. This property is of great importance for metamaterials science and can contribute substantially to the present search for simple and inexpensive left handed media. Moreover the negative value of the total change in absorption coefficient may be used for developing optical device such as maser at different frequency regime.

Temperature and Polarization Dependence of the Optical Absorption in ZnGeP2 at two Micrometers

1993 ◽  
Vol 325 ◽  
Author(s):  
M. Shah ◽  
M. C. Ohmer ◽  
D. W. Fischer ◽  
N. C. Fernelius ◽  
M. O. Manasreh ◽  
...  
Keyword(s):  
Optical Absorption ◽  
Absorption Coefficient ◽  
Polarization Dependence ◽  
Type I ◽  
Optical Parametric Oscillators ◽  
Absorption Coefficients ◽  
Parametric Oscillators ◽  
The Face ◽  
Significant Temperature ◽  
First Time

AbstractThe temperature and polarization dependence of the optical absorption in ZnGeP2 at two micrometers is reported for the first time over the temperature range from 10K to 300K. The radiation was normally incident upon the face of a cubic sample which contained the c-axis. The absorption of o-rays (E parallel to c), and erays (E perpendicular to c) was determined. It was found that the e-ray absorption coefficient was always significantly larger than the o-ray absorption coefficient and that it had a less significant temperature dependence. For example, the ratio of e-ray to o-ray absorption coefficient was approximately two at 300K and five at 77K. Correspondingly the o-ray absorption coefficients were reduced upon cooling to 77K by a factor of 2.5, while the e-ray absorption coefficients were reduced only slightly (10%-20%). These results indicate that for Type I optical parametric oscillators (OPOs) which use an oray pump beam, that performance may be improved by cooling the crystal.

MAXIMUM DYNAMICAL DISORDER IN AMORPHOUS GaAs

1994 ◽  
Vol 08 (03) ◽  
pp. 169-172 ◽  
Author(s):  
M.A. GRADO CAFFARO ◽  
M. GRADO CAFFARO
Keyword(s):  
Optical Absorption ◽  
Absorption Coefficient ◽  
Density Of States ◽  
Far Infrared ◽  
Conduction Band Edge ◽  
Infrared Range ◽  
Phonon Density ◽  
Phonon Density Of States ◽  
Low Frequencies ◽  
Dynamical Disorder

Maximum dynamical disorder in amorphous gallium arsenide is investigated in a special way. In particular, this maximum disorder refers to distance and it is investigated in the context of optical absorption at very low frequencies in the far-infrared range when the photon energy is larger than 2Ec, Ec being the energy at the conduction band edge. Absorption coefficient is calculated and compared with experimental work. Phonon density of states is also evaluated.

OPTICAL CHARACTERISATION OF THERMALLY EVAPORATED NICKEL PHTHALOCYANINE THIN FILMS

2004 ◽  
Vol 18 (03) ◽  
pp. 421-434 ◽  
Author(s):  
M. M. EL-NAHASS ◽  
K. F. ABD-EL-RAHMAN ◽  
A. A. M. FARAG ◽  
A. A. A. DARWISH
Keyword(s):  
Thin Films ◽  
Optical Absorption ◽  
Absorption Coefficient ◽  
Dielectric Constants ◽  
Optical Absorption Coefficient ◽  
Published Data ◽  
Dipole Strength ◽  
Dispersion Parameters ◽  
Absorption Bands ◽  
Nickel Phthalocyanine

Optical properties of thermally evaporated nickel phthalocyanine thin films have been characterised using spectrophotometric measurements of transmittance and reflectance in spectral range 200–2100 nm. The refractive index n and the absorption index k were calculated. Some of the optical absorption parameters, namely optical absorption coefficient (α), molar extinction coefficient (ε molar ), oscillator strength (f), electric dipole strength (q2) and absorption half bandwidth (Δλ) of the principal optical transitions have been also evaluated. The analysis of the spectral behaviour of the absorption coefficient (α), in the absorption region revealed indirect transitions. The fundamental and the onset energy gaps were estimated as 2.77±0.02 eV and 1.58±0.01 eV, respectively. According to the analysis of dispersion curves, the dielectric constants and dispersion parameters were obtained. The absorption measurements recorded in the UV–VIS region show two well defined absorption bands of phthalocyanine molecule, namely the Soret band (B) and the Q band. The Q band shows its characteristic splitting (Davydov splitting), and ΔQ was obtained as 0.21 eV. Discussion of the obtained results and their comparison with the previous published data are also given.

Nonlinear optical absorption in the core shell nanowire

2017 ◽  
Vol 31 (23) ◽  
pp. 1750164 ◽  
Author(s):  
Mohammad Kouhi
Keyword(s):  
Refractive Index ◽  
Relaxation Time ◽  
Optical Absorption ◽  
Absorption Coefficient ◽  
Shell Thickness ◽  
Refractive Index Change ◽  
Resonance Wavelength ◽  
Core Shell ◽  
Core Radius ◽  
Absorption Coefficients

In this paper, the effect of incident light intensity, relaxation time, core radius and shell thickness on linear, nonlinear, total optical absorption coefficients and refractive index changes in [Formula: see text] core–shell nanowire are theoretically investigated. The presented nanostructure is a cylindrical quantum wire including a shell around the cylinder core. By numerical solution of Schrödinger equation in the cylindrical coordinates with effective mass approximation, the optical absorption coefficients are calculated. The results show that the magnitude of optical absorption coefficients can be adjusted by varying the relaxation time. The positions of resonant peaks of optical absorption coefficients are redshifted by increase of core radius due to decrease of the energy difference between two energy levels. With increase of shell thickness initially, the resonance wavelength of absorption coefficient increases (redshift) and magnitude of absorption coefficient decreases. Then with more increases of the shell thickness, redshifting of resonance wavelength is stopped and magnitude of absorption coefficient is increased. There is a significant increase in the refractive index change with increase of relaxation time.

scholarly journals OPTICAL ABSORPTION AND EPR STUDY OF TRANSITION METAL IONS DOPED PHOSPHATE GLASSES

1996 ◽  
Vol 6 (0) ◽  
pp. 241-244 ◽  
Author(s):  
MOHAMED HAOUARI ◽  
HAFEDH BEN OUADA ◽  
HASSEN MAAREF ◽  
HUBERT HOMMEL ◽  
ANDRE PIERRE LEGRAND
Keyword(s):  
Transition Metal ◽  
Optical Absorption ◽  
Metal Ions ◽  
Transition Metal Ions ◽  
Phosphate Glasses

Magnetic Volume Effect of Hydrogen Diffusion in Palladium

2020 ◽  
Vol 310 ◽  
pp. 29-33
Author(s):  
Sarantuya Nasantogtokh ◽  
Xin Cui ◽  
Zhi Ping Wang
Keyword(s):  
Transition Metal ◽  
Density Of States ◽  
Density Functional ◽  
Hydrogen Diffusion ◽  
Magnetic Moments ◽  
Interstitial Site ◽  
Volume Effect ◽  
Face Centered Cubic ◽  
Hydrogen Atoms ◽  
Octahedral Interstitial Site

The electronic and magnetic properties of palladium hydrogen are investigated using first-principles spin-polarized density functional theory. By studying the magnetic moments and electronic structures of hydrogen atoms diffusing in face-centered cubic structure of transition metal Pd, we found that the results of magnetic moments are exactly the same in the two direct octahedral interstitial site-octahedral interstitial site diffusion paths-i.e. the magnetic moments are the largest in the octahedral interstitial site, and the magnetic moments are the lowest in saddle point positions. We also studied on the density of states of some special points, with the result that the density of states near the Fermi level is mainly contributed by 4d electrons of Pd and the change of magnetic moments with the cell volume in the unit cell of transition metal Pd with a hydrogen atom.

scholarly journals Electronic and optical properties of vacancy ordered double perovskites A2BX6 (A = Rb, Cs; B = Sn, Pd, Pt; and X = Cl, Br, I): a first principles study

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Muhammad Faizan ◽  
K. C. Bhamu ◽  
Ghulam Murtaza ◽  
Xin He ◽  
Neeraj Kulhari ◽  
...  
Keyword(s):  
Optical Properties ◽  
Band Gap ◽  
First Principles ◽  
Density Functional ◽  
Perovskite Solar Cells ◽  
Dielectric Constants ◽  
Maximum Efficiency ◽  
Exchange Potential ◽  
Double Perovskites ◽  
Electronic And Optical Properties

AbstractThe highly successful PBE functional and the modified Becke–Johnson exchange potential were used to calculate the structural, electronic, and optical properties of the vacancy-ordered double perovskites A2BX6 (A = Rb, Cs; B = Sn, Pd, Pt; X = Cl, Br, and I) using the density functional theory, a first principles approach. The convex hull approach was used to check the thermodynamic stability of the compounds. The calculated parameters (lattice constants, band gap, and bond lengths) are in tune with the available experimental and theoretical results. The compounds, Rb2PdBr6 and Cs2PtI6, exhibit band gaps within the optimal range of 0.9–1.6 eV, required for the single-junction photovoltaic applications. The photovoltaic efficiency of the studied materials was assessed using the spectroscopic-limited-maximum-efficiency (SLME) metric as well as the optical properties. The ideal band gap, high dielectric constants, and optimum light absorption of these perovskites make them suitable for high performance single and multi-junction perovskite solar cells.

Sign in / Sign up

Export Citation Format

Share Document