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Computational determination of structural, electronic, optical, thermoelectric and thermodynamic properties of hybrid perovskite CH3CH2NH3GeI3: An emerging material for photovoltaic cell
摘要： Owing to high power conversion efficiency and low-cost, methyl-ammonium lead-based halide (viz. CH3NH3PbI3) Perovskites have been emerging as the innovative candidate in the development of optoelectronic devices. However, the toxic lead in these materials is a major hurdle in its commercialization. Thus, there is an urgent need to replace lead with an appropriate element. Ethyl-ammonium based lead-free hybrid halide perovskites may be an alternative photovoltaic (PV) absorber material with appropriate band gap, high stability and non-toxic properties. Herein, we have investigated structural, electronic, optical, thermoelectric and thermodynamic properties of ethyl-ammonium germanium iodide (CH3CH2NH3GeI3 or EAGeI3) by full-potential augmented plane wave (FP-LAPW) method as implemented in the WIEN2k code within the density functional theory (DFT). In this paper, we have found that EAGeI3 has direct band gap of 1.3 eV and high absorption coefficient greater than 104 cm-1 and indicating its suitability as PV absorber material. We have also calculated thermoelectric coefficients as a function of carrier concentration, chemical potential and temperature. The thermodynamic calculations have been done within the quasi-harmonic approximation. As EAGeI3 has been studied first time for PV applications, the present study may open a new vista for more exhaustive experimental and theoretical investigations in search of non-toxic and eco-friendly PV materials.
关键词： absorption coefficient,Seebeck Coefficient,Ethyl-ammonium based hybrid perovskite,figure of merit,band gap
更新于2025-09-23 15:21:01
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Numerical analysis of earth-abundant Cu2ZnSn(SxSe1-x)4 solar cells based on Spectroscopic Ellipsometry results by using SCAPS-1D
摘要： Mixed chalcogenide CZTSSe with earth abundant elements, inexpensive, environmental-friendly and impressive photovoltaic performance is a promising absorber material for kesterite thin film solar cells of third generation. In this work, a numerical simulation of p-CZTSSe/n-CdS heterojunction solar cells have been presented using one dimensional Solar Capacitance Simulator. The influence of composition, absorber thickness, defect density and working temperature on Voc, Jsc, FF and power conversion efficiency has been investigated. The optimized cell shows 23.16% efficiency with a Voc ~ 0.724 V corresponding to 40% of the ratio.
关键词： Composition and Spectroscopic Ellipsometry,Absorption coefficient,CZTSSe,Thin film solar cell,Third generation,SCAPS,Efficiency
更新于2025-09-23 15:21:01
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Size and Temperature Dependent Intraband Optical Properties of Heavily <i>n-</i> Doped PbS Colloidal Quantum Dot Solid-State Films
摘要： Steady-state access to intraband transitions in colloidal quantum dots (CQDs), via doping, permits exploitation of the electromagnetic spectrum at energies below the band gap. CQD intraband optoelectronics allows envisaging cheap mid- and long-wavelength infrared photodetectors and light-emitting devices, which today employ epitaxial materials. As intraband devices start to emerge, thorough studies of the basic properties of intraband transitions in different CQD materials are needed to guide technological research. In this work, we investigate the size and temperature dependence of the intraband transition in heavily n-doped PbS quantum dot (QD) films. In the studied QD size range (5–8 nm), the intraband energy spans from 209 meV to 151 meV. We measure the intraband absorption coefficient of heavily doped PbS QD films to be around 2 × 104 cm-1, proving that intraband absorption is as strong as interband absorption. We demonstrate a negative dependence of the intraband energy with temperature, in contrast to the positive dependence of the interband transition. Also opposite to the interband case, the temperature dependence of the intraband energy increases with decreasing size, going from -29 μeV/K to -49 μeV/K in the studied size range.
关键词： temperature dependence,absorption coefficient,intraband,lead sulphide,quantum dots
更新于2025-09-23 15:21:01
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The mean energy transfer and collisional absorption coefficient of high power laser in plasma
摘要： The absorption coefficient of high power laser incident normally onto a plasma medium is studied when electron energy distribution obeys non-extensive function. The variation of the absorption coefficient with the incident laser intensity is investigated for different electron temperatures as well as different non-extensive distribution parameter (q). The variation of the absorption coefficient with plasma density is also investigated for different q values for constant temperature. Furthermore the mean rate of energy absorption is evaluated as function of the incident laser intensity for different electron temperatures and q values. The results are compared with ones obtained in Maxwellian case and differences are shown in the corresponding diagrams.
关键词： Non-extensive distribution,Absorption coefficient,Inverse bremsstrahlung,Laser intensity,Maxwellian distribution
更新于2025-09-23 15:21:01
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The relation between magnesium evaporation and laser absorption and weld penetration in pulsed laser welding of aluminum alloys: Experimental and numerical investigations
摘要： It is observed that in laser welding of aluminum alloys, magnesium can evaporate, and the weld penetration is dependent on Mg content of the alloy and Mg loss from the weld pool. In this research, it is proposed that the presence of Mg not in the base metal alloy, but rather the presence of Mg vapor in the plasma plume over the weld pool affects the laser absorption, and it is through this phenomenon that the weld profile and penetration is affected. Numerical simulation was performed to determine the relationship between the weld profile to estimate the effective laser absorption coefficient of four Al alloys and in parallel EPMA technique was used to determine the Mg losses of the weld metals. The combined analysis of the results showed that increasing the laser pulse energy (decreasing laser pulse frequency), Mg evaporation is increased, and that, in turn, increased the effective laser absorption coefficient. However, more laser power absorption does not necessarily mean more weld penetration. Laser absorption results in weld penetration, once the threshold Mg evaporation rate of 200 × ?10 6g/cm2 is passed.
关键词： Pulsed laser welding,Effective absorption coefficient,Aluminum alloys,Evaporation,Magnesium content,Penetration depth
更新于2025-09-23 15:21:01
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Investigation of structural, electronic, optical and thermoelectric properties of Ethylammonium tin iodide (CH3CH2NH3SnI3): An appropriate hybrid material for photovoltaic application
摘要： Hybrid halide Perovskites have been emerging as the innovative candidate in the development of optoelectronic devices. Ethyl-ammonium based hybrid halide perovskites have been admirable compounds regarding low band gap, high stability and non-toxic properties instead of methyl-ammonium based hybrid halide perovskites. Herein, we have investigated structural, electronic, optical and thermoelectric (TE) properties of ethyl-ammonium tin iodide (CH3CH2NH3SnI3) by full-potential linearized augmented plane wave plus local orbital (FP-LAPW t lo) method as implemented in the WIEN2k code within the density functional theory (DFT). The PBE-GGA, PBE-sol-GGA and TB-mBJ-GGA exchange-correlation potentials have been used to calculate the density of states and band structure of ethyl ammonium tin iodide (EASnI3) and found that it is a direct band gap semiconductor. We have calculated optical parameters such as dielectric function, absorption coefficient, refractive index, extinction coefficient, Eloss, optical reflectivity and optical conductivity for photon energies in the range 0–25 eV. We have also calculated transport coefficients (Seebeck coefficient, the figure of merit, power factor, electrical conductivity, thermal conductivity) as a function of carrier concentration, chemical potential and temperature. Most of the investigated parameters are being reported for the first time. The present study establishes that ethyl-ammonium tin iodide (EASnI3) offers high absorption coefficient, high Seebeck coefficient, etc. This makes it a prospective material for cost effective photovoltaic device applications to overcome environmental instabilities.
关键词： Dielectric constant,Absorption coefficient,Ethyl-ammonium based hybrid perovskite,Band gap
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Sozopol, Bulgaria (2019.9.6-2019.9.8)] 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Spatial inhomogeneity of the absorption and re-emission properties of an optically active medium in a resonator
摘要： The spatial inhomogeneity of absorption coefficient of the space between mirrors, filled by an optically active gas, is analyzed in quantum optical terms. It was theoretically shown, that the quantization of electromagnetic field in a cavity (optical resonator) can reveal the spatial inhomogeneity of absorption or re-emission ability of the optically active medium. It appears from the analytical calculations, the inhomogeneity is caused by the Doppler frequency shifts (including recoil effects) during the atom-photon collisions and the non-zero initial frequency width of the scanning signal. The proposed analytical representation of the absorption coefficient through the additive quantum optical terms gives deeper insight into intrinsic processes in the interacting with light matter.
关键词： absorption coefficient,many-body system,inhomogeneity,quantum optics
更新于2025-09-23 15:19:57
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Effect of applied electric field on the nonlinear optical properties of modulation-doped GaAs/Al Ga1-As double quantum well
摘要： In the present study, the effects of varying doping concentration and applied electric field on the intersubband-related optical absorption and relative refractive index change coefficients in modulation-doped GaAs/AlxGa1?xAs double quantum wells are theoretically investigated. The allowed energy levels and the corresponding wave-functions are calculated by solving the Schr?dinger and Poisson equations self-consistently within the framework of the effective-mass and parabolic band approximations. The optical coefficients are evaluated using the compact density matrix formalism within an iterative procedure. The numerical results are presented for two different doping concentration and several values of the electric field. They show that both the peak position and the magnitude of the calculated total optical absorption coefficients and refractive index changes are significantly affected by the applied electric field and the doping concentration. The treatment is suitable to consider the general problem with different wells and barrier sizes, although the barrier width should preferably be small enough as to allow for an effective inter-well coupling.
关键词： Relative refractive index change,Modulation-doped QW,Absorption coefficient,self-consistent method
更新于2025-09-23 15:19:57
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Variations in Spectral Absorption Properties of Phytoplankton, Non-algal Particles and Chromophoric Dissolved Organic Matter in Lake Qiandaohu
摘要： Light absorption by phytoplankton, non-algal particles (NAP) and chromophoric dissolved organic matter (CDOM) was investigated at 90 sites of a clear, deep artificial lake (Lake Qiandaohu) to study natural variability of absorption coefficients. Our study shows that CDOM absorption is a major contributor to the total absorption signal in Lake Qiandaohu during all seasons, except autumn when it has an equivalent contribution as total particle absorption. The exponential slope of CDOM absorption varies within a narrow range around a mean value of 0.0164 nm?1 (sd = 0.00176 nm?1). Our study finds some evidence for the autochthonous production of CDOM in winter and spring. Absorption by phytoplankton, and therefore its contribution to total absorption, is generally greatest in spring, suggesting that phytoplankton growth in Lake Qiandaohu occurs predominantly in the spring. Phytoplankton absorption in freshwater lakes generally has a direct relationship with chlorophyll-a concentration, similar to the one established for open ocean waters. The NAP absorption, whose relative contribution to total absorption is highest in summer, has a spectral shape that can be well fitted by an exponential function with an average slope of 0.0065 nm?1 (sd = 0.00076 nm?1). There is significant spatial variability present in the summer of Lake Qiandaohu, especially in the northwestern and southwestern extremes where the optical properties of the water column are strongly affected by the presence of allochthonous matter. Variations in the properties of the particle absorption spectra with depths provides evidence that the water column was vertically inhomogeneous and can be monitored with an optical measurement program. Moreover, the optical inhomogeneity in winter is less obvious. Our study will support the parameterization of the Bio-optical model for Lake Qiandaohu from in situ or remotely sensing aquatic color signals.
关键词： Lake Qiandaohu,variations,CDOM,phytoplankton,spectral absorption coefficient,non-algal particles
更新于2025-09-19 17:15:36
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Harnessing Brightness in Naphthalene Diimides
摘要： The development of brightly emissive compounds is of great research and commercial interest, with established and emerging applications across chemistry, biology, physics, medicine and engineering. Among the many types of molecules available, naphthalene diimides have been widely used for both fundamental photophysical studies and in practical applications that utilise information readout. The monomeric naphthalene diimide is weakly fluorescent, however through various methods of core-derivatisation, it can be developed to be highly fluorescent and further functionalised to add utility. In this review, we highlight recent advances made in naphthalene diimide chemistry that have led to development of molecules with improved optical properties, and the design strategies utilised to produce bright fluorescence emission as small molecules or in supramolecular architectures.
关键词： naphthalene diimides,fluorescence,molecular brightness,absorption coefficient,quantum yield
更新于2025-09-19 17:15:36