Search NASA⌕ Search

SEARCH · Search NASA

Results for “absorption coefficient”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Angular Selectivity of Amplitude-Phase Holographic Gratings in Polymer Material with Phenanthrenequinone

The values of the amplitudes of the refractive index and absorption coefficient modulations in volume hologram gratings, which were recorded in a polymer material with phenanthrenequinone (PQ), have been determined by the results of the approximation of the angular selectivity contours, which were measured at wavelengths of 450, 473, 532, and 633 nm before and after the development of holograms, resulting from the diffusion of PQ molecules in a glassy polymer. Immediately after recording, before the diffusion development, the holograms are mixed amplitude-phase in the PQ absorption spectral region and phase for the red light, which is not absorbed by it (633 nm), and become purely phase during the development regardless of the wavelength. The shape of the selectivity contour of the undeveloped hologram indicates the counterphase between the modulations of the absorption coefficient and refractive index, illustrating the concept of complementary gratings, on which the principle of hologram formation in the material under consideration is based.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS2005

Quantitative Electron Probe Microanalysis: State of the Art

Quantitative electron-probe microanalysis (EPMA) has improved due to better instrument design and X-ray correction methods. Design improvement of the electron column and X-ray spectrometer has resulted in measurement precision that exceeds analytical accuracy. Wavelength-dispersive spectrometer (WDS) have layered-dispersive diffraction crystals with improved light-element sensitivity. Newer energy-dispersive spectrometers (EDS) have Si-drift detector elements, thin window designs, and digital processing electronics with X-ray throughput approaching that of WDS Systems. Using these systems, digital X-ray mapping coupled with spectrum imaging is a powerful compositional mapping tool. Improvements in analytical accuracy are due to better X-ray correction algorithms, mass absorption coefficient data sets,and analysis method for complex geometries. ZAF algorithms have ban superceded by Phi(pz) algorithms that better model the depth distribution of primary X-ray production. Complex thin film and particle geometries are treated using Phi(pz) algorithms, end results agree well with Monte Carlo simulations. For geological materials, X-ray absorption dominates the corretions end depends on the accuracy of mass absorption coefficient (MAC) data sets. However, few MACs have been experimentally measured, and the use of fitted coefficients continues due to general success of the analytical technique. A polynomial formulation of the Bence-Albec alpha-factor technique, calibrated using Phi(pz) algorithms, is used to critically evaluate accuracy issues and can be also be used for high 2% relative and is limited by measurement precision for ideal cases, but for many elements the analytical accuracy is unproven. The EPMA technique has improved to the point where it is frequently used instead of the petrogaphic microscope for reconnaissance work. Examples of stagnant research areas are: WDS detector design characterization of calibration standards, and the need for more complete treatment of the continuum X-ray fluorescence correction.

Carpernter, P. K.↗
DOE OSTI2017

Self-Referenced Method for Estimating Refractive Index and Absolute Absorption of Loose Semiconductor Powders

The absolute absorption coefficient, α(E), is a critical design parameter for devices using semiconductors for light harvesting associated with renewable energy production, both for classic technologies such as photovoltaics and for emerging technologies such as direct solar fuel production. While α(E) is well-known for many classic simple semiconductors used in photovoltaic applications, the absolute values of α(E) are typically unknown for the complex semiconductors being explored for solar fuel production due to the absence of single crystals or crystalline epitaxial films that are needed for conventional methods of determining α(E). In this work, a simple self-referenced method for estimating both the refractive indices, n(E), and absolute absorption coefficients, α(E), for loose powder samples using diffuse reflectance data is demonstrated. In this method, the sample refractive index can be deduced by refining n to maximize the agreement between the relative absorption spectrum calculated from bidirectional reflectance data (calculated through a Hapke transform which depends on n) and integrating sphere diffuse reflectance data (calculated through a Kubleka–Munk transform which does not depend on n). This new method can be quickly used to screen the suitability of emerging semiconductor systems for light-harvesting applications. The effectiveness of this approach is tested using the simple classic semiconductors Ge and Fe 2 O 3 as well as the complex semiconductors La 2 MoO 5 and La 4 Mo 2 O 11 . The method is shown to work well for powders with a narrow size distribution (exemplified by Fe 2 O 3 ) and to be ineffective for semiconductors with a broad size distribution (exemplified by Ge). As such, it provides a means for rapidly estimating the absolute optical properties of complex solids which are only available as loose powders.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Thickness-dependent dispersion parameters, energy gap and nonlinear refractive index of ZnSe thin films

Highlights: • Combined experimental and theoretical researches on ZnSe Thin Films. • The film thickness and refractive index were determined using envelope method. • The absorption coefficient and the energy gap were calculated. • Dispersion parameters were determined using Wemple-DiDomenico relation. • The third order susceptibility and nonlinear refractive index were calculated. - Abstract: Zinc selenide (ZnSe) thin films with different thicknesses were evaporated onto glass substrates using the thermal evaporation technique. X-ray diffraction analysis confirmed that both the film and powder have cubic zinc-blende structure. The fundamental optical parameters like absorption coefficient, extinction coefficient and band gap were evaluated in transparent region of transmittance and reflectance spectrum. The optical transition of the films was found to be allowed, where the energy gap increased from 2.576 to 2.702 eV with increasing film thickness. Also, the refractive index value increase with increasing film thickness. The refractive indices evaluated through envelope method were extrapolated by Cauchy dispersion relationship over the whole spectra range. Additionally, the dispersion of refractive index was determined in terms of Wemple-DiDomenico single oscillator model. Third order susceptibility and nonlinear refractive index were determined for different thickness of ZnSe thin films.

36 MATERIALS SCIENCE↗
NASA NTRS1980

Infrared radiative properties of tropical cirrus clouds inferred with aircraft measurements

Longwave emissivities and the vertical profile of cooling rates of tropical cirrus clouds are determined using broadband hemispheric irradiance data. Additionally, a broadband mass absorption coefficient is defined and used to relate emissivity to water content. The data used were collected by the National Center for Atmospheric Research (NCAR) Sabreliner during the GARP Atlantic Tropical Experiment (GATE) in the summer of 1974. Three case studies are analyzed showing that these tropical cirrus clouds approached an emissivity of 1.0 within a vertical distance of 1.0 km. Broadband mass absorption coefficients ranging from 0.076 to 0.096 sq m per g are derived. A comparison of these results with other work suggests that tropical cirrus cloud emissivities may be significantly larger than heretofore believed. Ice water content of the clouds were deduced from data collected by a one-dimensional particle spectrometer. Analyses of the ice water content and the observed particle size distributions are presented.

Griffith, K. T.↗
DOE OSTI2017

Gamma ray irradiation-induced variations in structure and optical properties of cerium/titanium-doped oxyfluoride transparent glass-ceramics

Highlights: • CeO{sub 2} favors CaF{sub 2} crystallization while TiO{sub 2} suppresses CaF{sub 2} crystallization. • Doping TiO{sub 2} helps reduce intrinsic coloring caused by CeO{sub 2}. • Doping CeO{sub 2} and/or TiO{sub 2} improves defects saturation over irradiation does. • Doping CeO{sub 2} allows lower radiation induced absorption coefficient than co-doping CeO{sub 2}/TiO{sub 2}. - Abstract: CeO{sub 2}/TiO{sub 2}-doped oxyfluoride transparent glass ceramics with a composition of 45SiO{sub 2}–20Al{sub 2}O{sub 3}–10CaO–25CaF{sub 2} were synthesized and irradiated by gamma ray. The effects of CeO{sub 2}/TiO{sub 2} on the structure and optical properties of the samples before and after irradiation were investigated. Doping with CeO{sub 2} causes network depolymerization and conversion of [AlO{sub 6}] to [AlO{sub 4}], enlarging the percolation region and promoting CaF{sub 2} crystallization. Co-doping with CeO{sub 2}/TiO{sub 2} helps reduce the intrinsic coloring of transparent glass ceramics containing only CeO{sub 2}, and the addition of TiO{sub 2} enhances network interconnectivity, suppressing CaF{sub 2} crystallization. Doping with CeO{sub 2} and/or TiO{sub 2} improves the structural stability of transparent glass ceramics upon irradiation and maintains the optical band gap and Urbach energy constant due to the defect saturation over the irradiation dose. Doping solely with CeO{sub 2} allows for a lower radiation-induced absorption coefficient than co-doping CeO{sub 2}/TiO{sub 2} because of the enhanced crystallization induced by CeO{sub 2} and balanceable light absorption of polyvalent cerium ions.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Dynamics of Electronic States and Magnetoabsorption in 3D Topological Insulators in a Quantizing Magnetic Field

Quantum states have been calculated analytically; the dynamics of a wave packet in a magnetic field has been investigated, and the optical absorption coefficient has been calculated for surface states in 3D topological insulators of the Bi{sub 2}Te{sub 3} family. We have detected a qualitative effect of the hexagonal warping of the spectrum on the structure of wavefunctions at the Landau levels, its manifestation in the features of the wave packet dynamics in a quantizing magnetic field, as well as in the frequency dependence of the optical absorption coefficient, in which new peaks that are absent in the isotropic model of the spectrum appear depending on the polarization of the incident wave. The effects considered here can be manifested in the optical and transport experiments with topological insulators, which makes it possible to determine the parameters of their band structure.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Light Absorption by Brown Carbon over the South-East Atlantic Ocean

Biomass burning emissions often contain brown carbon (BrC), which represents a large family of light-absorbing organics that is chemically complex and therefore difficult to estimate their absorption of incoming solar radiation, resulting in large uncertainties in the estimation of the global direct radiative effect of aerosols. Here we investigate the contribution of BrC to the total light absorption of biomass burning aerosols over the South-East Atlantic Ocean with different optical models utilizing a suite of airborne measurements from the ORACLES 2018 campaign by introducing an effective refractive index of black carbon (BC), m eBC = n eBC +ik eBC , that accounts for all possible absorbing components at 660 nm wavelength to facilitate the attribution of absorption at shorter wavelengths. Most values of the imaginary part of the refractive index, k eBC , were larger than those commonly used for BC from biomass burning emissions, suggesting contributions from absorbers beyond BC at 660 nm. The TEM-EDX single particle analysis further suggests that these long-wavelength absorbers might include iron oxides, as iron is found to be present only when large values of k eBC are derived. Using this effective BC refractive index, we find that the contribution of BrC to the total absorption at 470 nm (R BrC,470 ) ranges from ~5–15 %, with the organic aerosol mass absorption coefficient (MAC OA,470 ) at this wavelength ranging from 0.25 ± 0.34 m 2 g -1 to 0.43 ± 0.12 m 2 g -1 . The core-shell model yielded much higher estimates of MAC OA,470 and R BrC,470 than homogeneous mixing models, underscoring the importance of model treatment. Another key finding was that estimates of the BrC contribution at 470 nm from the commonly used AAE (absorption Ångström exponent) attribution method (< 5 %) are much lower than the BrC contribution estimates (R BrC,470 ) using our new methodology that accounts for contributions from both BrC and non-carbonaceous, long-wavelength absorbers, such as magnetite. Thus, it is recommended that application of any optical properties-based attribution method use absorption coefficients at the longest possible wavelength to minimize the influence of BrC at the long wavelength and to account for potential contributions from other absorbing materials.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2017

Low-temperature atomic layer deposition of CuSbS 2 for thin-film photovoltaics

Copper antimony sulfide (CuSbS 2 ) has been gaining traction as an earth-abundant absorber for thin-film photovoltaics given its near ideal band gap for solar energy conversion (~1.5 eV), large absorption coefficient (>10 4 cm –1 ), and elemental abundance. Through careful in situ analysis of the deposition conditions, a low-temperature route to CuSbS 2 thin films via atomic layer deposition has been developed. After a short (15 min) post process anneal at 225 °C, the ALD-grown CuSbS 2 films were crystalline with micron-sized grains, exhibited a band gap of 1.6 eV and an absorption coefficient >10 4 cm –1 , as well as a hole concentration of 10 15 cm –3 . Finally, the ALD-grown CuSbS 2 films were paired with ALD-grown TiO 2 to form a photovoltaic device. This photovoltaic device architecture represents one of a very limited number of Cd-free CuSbS 2 PV device stacks reported to date, and it is the first to demonstrate an open-circuit voltage on par with CuSbS 2 /CdS heterojunction PV devices. As a result, while far from optimized, this work demonstrates the potential for ALD-grown CuSbS 2 thin films in environmentally benign photovoltaics.

36 MATERIALS SCIENCE↗
NASA NTRS1979

Acoustical properties of highly porous fibrous materials

Highly porous, fibrous bulk sound absorbing materials are studied with a view toward understanding their acoustical properties and performance in a wide variety of applications including liners of flow ducts. The basis and criteria for decoupling of acoustic waves in the pores of the frame and compressional waves in the frame structure are established. The equations of motion are recast in a form that elucidates the coupling mechanisms. The normal incidence surface impedance and absorption coefficient of two types of Kevlar 29 and an open celled foam material are studied. Experimental values and theoretical results are brought into agreement when the structure factor is selected to provide a fit to the experimental data. A parametric procedure for achieving that fit is established. Both a bulk material quality factor and a high frequency impedance level are required to characterize the real and imaginary part of the surface impedance and absorption coefficient. A derivation of the concepts of equivalent density and dynamic resistance is presented.

Lambert, R. F.↗
DOE OSTI2021

AlSb as a material for high index contrast nanophotonics

High contrast materials, i.e., materials with a high refractive index and low optical loss, are of wide interest for nanophotonics and metasurface designs at optical and near infrared wavelengths. We explore aluminum antimonide (AlSb) as a high contrast nanophotonic material, using the design of high contrast gratings (HCGs) for low loss dielectric mirrors as an example. The high index of refraction and low absorption coefficient of AlSb in the visible wavelength range enable designs of HCGs that can be effectively optimized to form mirrors with 93.5% reflectivity at red visible wavelengths. We detail a co-sputtering synthesis method for AlSb films, and achieve our target high index of refraction of 3.5 for 635 nm light. We also find that the high sensitivity of AlSb oxidation requires specific handling procedures in developing deposition processes to yield a near zero absorption coefficient.

Bauser, Haley C.↗
NASA NTRS1988

Comparison of vibration dissociation coupling and radiative heat transfer models for AOTV/AFE flowfields

A series of detailed studies comparing various vibration dissociation coupling models, reaction systems and rates, and radiative heating models has been conducted for the nonequilibrium stagnation region of an AFE/AOTV vehicle. Atomic and molecular nonequilibrium radiation correction factors have been developed and applied to various absorption coefficient step models, and a modified vibration dissociation coupling model has been shown to yield good vibration/electronic temperature and concentration profiles. While results indicate sensitivity to the choice of vibration dissociation coupling model and to the nitrogen electron impact ionization rate, by proper combinations accurate flowfield and radiative heating results can be obtained. These results indicate that nonequilibrium effects significantly affect the flowfield and the radiative heat transfer. However, additional work is needed in ionization chemistry and absorption coefficient modeling.

Carlson, Leland A.↗
NASA NTRS1977

Atmospheric absorption of high frequency noise and application to fractional-octave bands

Pure tone sound absorption coefficients were measured at 1/12 octave intervals from 4 to 100 KHz at 5.5K temperature intervals between 255.4 and 310.9 K and at 10 percent relative humidity increments between 0 percent and saturation in a large cylindrical tube (i.d., 25.4 cm; length, 4.8 m). Special solid-dielectric capacitance transducers, one to generate bursts of sound waves and one to terminate the sound path and detect the tone bursts, were constructed to fit inside the tube. The absorption was measured by varying the transmitter receiver separation from 1 to 4 m and observing the decay of multiple reflections or change in amplitude of the first received burst. The resulting absorption was compared with that from a proposed procedure for computing sound absorption in still air. Absorption of bands of noise was numerically computed by using the pure tone results. The results depended on spectrum shape, on filter type, and nonlinearly on propagation distance. For some of the cases considered, comparison with the extrapolation of ARP-866A showed a difference as large as a factor of 2. However, for many cases, the absorption for a finite band was nearly equal to the pure tone absorption at the center frequency of the band. A recommended prediction procedure is described for 1/3 octave band absorption coefficients.

Shields, F. D.↗
DOE OSTI2019

Optimal absorber thickness in long-wave multiple-stage detector

The detectivity characteristics of interband cascade infrared type-II superlattice detectors for long-wave infrared detection (λ{sub cut-off} = 8 μm at room temperature) are discussed. We present comparison of two superlattices: InAs/GaSb and InAs/InAsSb, assuming the characteristic parameters—absorption coefficients α and carrier lifetimes τ published in literature. Dependence of the Johnson-noise limited detectivity on the absorber thickness for a different number of stages is reported. Higher detectivity D{sup *} value can be achieved by increasing the carrier lifetime. However, for detectors based on type-II InAs/GaSb superlattice increasing the carrier lifetime up to 25 ns leads to a situation in which one stage is preferred, i.e. for detector with a single absorber, we obtain the highest detectivity value. In the case of InAs/InAsSb material, the situation is similar for τ ≥ 80 ns. We have shown that the optimal absorber thickness at which the highest detectivity values are obtained depends not only on the absorption coefficient α and the number of stages N{sub S}, but also on the carrier diffusion length L. According to a calculations, cascade detectors based on Ga-free material should have much higher optimal absorber thicknesses than materials based on InAs/GaSb.

42 ENGINEERING↗
NASA NTRS1989

Infrared spectra of crystalline and glassy silicates and application to interstellar dust

The infrared spectra of crystalline minerals predicted in theoretical condensation sequences do not match the astronomical observations. Since the astronomical spectra are a closer match to glassy silicates, the authors undertook a study to measure the infrared spectra of glassy silicates that have compositions similar to silicate minerals predicted in theoretical condensation sequences. The data should support observations aimed at elucidating condensation chemistry in dust forming regions. The authors measured the mass absorption coefficients, from 2.5 to 25 microns, of ground samples of olivine, diopside, and serpentine and also smoke samples that were prepared from these minerals. The smoke samples prepared in this way are predominantly glassy with nearly the same composition as the parent minerals. The crystalline samples consisted of pure olivine ((Fe(0.1)Mg(0.9))(2)SiO(4)), serpentine, diopside. Sample purity was confirmed by x ray diffraction. Each mineral was ground for 10 hours and a measured mass of the powder was mixed with KBr powder for absorption measurements using the method of Borghesi et a. (1985). The smoke samples were prepared from the same samples used for grinding by vaporizing the minerals using pulsed laser radiation in air. The smoke samples formed by condensation of the resulting vapor. The smoke settled onto infrared transparent KRS-5 substrates and onto a quartz crystal microbalance used to obtain mass measurements. A description of the preparation method is given in Stephens (1980). The glassy diopside showed only diffuse electron diffraction peaks and hence was nearly amorphous, while the serpentine smoke showed a weak diffraction pattern corresponding to MgO. The smoke from olivine showed a weak diffraction pattern corresponding to Fe2O3 and/or Fe3O4. The mass absorption coefficients, from 2.5 to 25 microns, of crystalline diopside, olivine, and serpentine and their corresponding smoke samples are shown in figures.

Stephens, John R.↗
NASA NTRS2014

Algorithm Development and Validation of CDOM Properties for Estuarine and Continental Shelf Waters Along the Northeastern U.S. Coast

An extensive set of field measurements have been collected throughout the continental margin of the northeastern U.S. from 2004 to 2011 to develop and validate ocean color satellite algorithms for the retrieval of the absorption coefficient of chromophoric dissolved organic matter (aCDOM) and CDOM spectral slopes for the 275:295 nm and 300:600 nm spectral range (S275:295 and S300:600). Remote sensing reflectance (Rrs) measurements computed from in-water radiometry profiles along with aCDOM() data are applied to develop several types of algorithms for the SeaWiFS and MODIS-Aqua ocean color satellite sensors, which involve least squares linear regression of aCDOM() with (1) Rrs band ratios, (2) quasi-analytical algorithm-based (QAA based) products of total absorption coefficients, (3) multiple Rrs bands within a multiple linear regression (MLR) analysis, and (4) diffuse attenuation coefficient (Kd). The relative error (mean absolute percent difference; MAPD) for the MLR retrievals of aCDOM(275), aCDOM(355), aCDOM(380), aCDOM(412) and aCDOM(443) for our study region range from 20.4-23.9 for MODIS-Aqua and 27.3-30 for SeaWiFS. Because of the narrower range of CDOM spectral slope values, the MAPD for the MLR S275:295 and QAA-based S300:600 algorithms are much lower ranging from 9.9 and 8.3 for SeaWiFS, respectively, and 8.7 and 6.3 for MODIS, respectively. Seasonal and spatial MODIS-Aqua and SeaWiFS distributions of aCDOM, S275:295 and S300:600 processed with these algorithms are consistent with field measurements and the processes that impact CDOM levels along the continental shelf of the northeastern U.S. Several satellite data processing factors correlate with higher uncertainty in satellite retrievals of aCDOM, S275:295 and S300:600 within the coastal ocean, including solar zenith angle, sensor viewing angle, and atmospheric products applied for atmospheric corrections. Algorithms that include ultraviolet Rrs bands provide a better fit to field measurements than algorithms without the ultraviolet Rrs bands. This suggests that satellite sensors with ultraviolet capability could provide better retrievals of CDOM. Because of the strong correlations between CDOM parameters and DOM constituents in the coastal ocean, satellite observations of CDOM parameters can be applied to study the distributions, sources and sinks of DOM, which are relevant for understanding the carbon cycle, modeling the Earth system, and to discern how the Earth is changing.

CDOM Properties↗
DOE OSTI2018

Te-doped perovskite NaTaO3 as a promising photocatalytic material for hydrogen production from water splitting driven by visible light

Highlights: • S, Se and Te-doped NaTaO{sub 3} is a promising material for photocatalytic water splitting. • Enhanced absorption coefficient in the visible light range is identified for Te-doped NaTaO{sub 3}. • Te-doped NaTaO{sub 3} exhibits higher electron and hole mobility than pristine NaTaO{sub 3}. - Abstract: The photocatalytic hydrogen production from water splitting can be achieved by using the pristine NaTaO{sub 3} experimentally, but the reaction cannot be driven by the visible light because of the wide band gap of NaTaO{sub 3}. The present work focuses on tuning the photocatalytic performance of NaTaO{sub 3} into the visible light range by doping S, Se, and Te elements. The obvious decrease in band energy gaps (E{sub g}s) and noticeable red-shift of the absorption edges are observed for the doped structures. The valence band maximum and conduction band minimum of the doped structures satisfy the requirement of the water splitting. Moreover, a significant enhancement of absorption coefficient in the visible light range is observed for the doped structure of Te@O. The calculated carrier mobility is used to evaluate the charge spatial separation of Te@O and the unusual increases and the obvious differences of the mobility of the electrons and holes are observed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

First principle study of structural, electronic, optical, and transport properties of ternary compounds NaGaX{sub 2} (X = S, Se, and Te) in tetragonal chalcopyrite phase

Eemploying the all electron full potential linearized augmented plane wave plus local orbital (FP-LAPW + lo) method based on density functional theory (DFT) structural, electronic, optical, and transport properties of compounds NaGaX{sub 2} (X = S, Se, and Te) in tetragonal phase have been investigated at ground state. The exchange-correlation effects have been included using the Wu Cohen (WC) generalized gradient approximation (GGA) and modified Becke–Johnson (mBJ) exchange potentials. Enthalpy of formation values ensure that crystal structures are stable in tetragonal chalcopyrite phase. Total and partial density of states, and band structures have been plotted to calculate electronic properties which exhibits direct band gap for all compounds. The electronic band gap of NaGaS{sub 2} (2.1 eV) is found to be higher than the electronic band gaps of NaGaSe{sub 2} (1.7 eV) and NaGaTe{sub 2} (1.2 eV) compounds. Using real and imaginary parts of the dielectric function, optical properties such as refractive index (n), extinction coefficient (k), reflectivity (R), absorption coefficient (α), and energy loss spectrum (L) were determined. Transport properties like Seebeck coefficient, thermal and electrical conductivities, figure of merit, and power factors have also been reported by combining the results from DFT and Boltzmann transport theory. The high absorption peaks in visible and ultraviolet regions of the energy spectrum and direct band gaps of these compounds ensure that three compounds are promising materials for photovoltaic applications.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗