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Using density functional theory, we have analyzed the ways and means of improving the minority carrier lifetime (MCL) by calculating the band structure dependent quantities contributing to the MCL. We have computationally modeled silicon doped with different elements like B, C, N, O, P, Ti, Fe, Ga, Ge, As, In, Sn, Sb, and Pt and looked at the effect of doping on MCL. In co-doping, the systems Si-B-Ga, Si-B-Ge, Si-B-2Ge, Si-B-Pt, Si-Ga-Ge, Si-Ga-2Ge, and Si-Ga-Pt are investigated. From our calculation, it is found that by doping and co-doping of Si with suitable elements having “s” and “p” electrons, there is a decrease in the recombination activity. The predicted effective minority carrier lifetime indicates the possibility of significant improvements. Based on the above studies, it is now maybe possible, with suitable choice of dopant and co-dopant material, to arrive at part of a standard production process for solar grade Si material. [ABSTRACT FROM AUTHOR]

The electronic structure and optical properties of AgIn1−xGaxY2 (Y = Se, Te) are investigated using first-principles calculations based on density functional theory. Both the local density approximation (LDA) and generalized gradient approximation (GGA) are employed in the calculation. The crystal structure of ternary semiconductors is the tetragonal chalcopyrite structure with space group I 4 ¯ 2d . The lattice parameters a(Å) and c(Å) are found to vary with the change in Ga composition. The energy gap across the Fermi level in the density of states plots shows that these materials are semiconductors. To compute accurate energy gap values, the LDA + U method is adopted. The calculated elastic constants indicate that these compounds are mechanically stable at normal pressure. The semiconducting nature of these materials may prove their applications in solar cells and photovoltaic absorbers. The optical parameters such as dielectric function, electron energy loss function, refractive index and reflectivity are computed. [ABSTRACT FROM AUTHOR]

The structural, electronic and mechanical properties of AgIn1−XGaXS2 (X = 0, 0.25, 0.50, 0.75, 1) chalcogenides are investigated. The crystal structure of ternary semiconductors is the chalcopyrite structure with space group I 4 ¯ 2 d . In this work, first principles calculations are carried out based on density functional theory within the local density approximation to analyze the structural, electronic and mechanical properties of chalcogenides. The calculated lattice constant values are in good agreement with the available data. The lattice constants and the energy gap value increase with the increase in concentration of Gallium (Ga) in AgIn1−XGaXS2. The electronic structure reveals that these materials are semiconductors. The calculated elastic constants indicate that these chalcogenide materials are mechanically stable at normal pressure. The semiconducting nature of these materials may prove their applications in solar cells and photovoltaic absorbers. [ABSTRACT FROM AUTHOR]

The structural property, electronic structure and optical properties of lead-based halide perovskites CsPbF3-yIy (y = 0, 1, 2) are investigated. The computed electronic structure profile of CsPbF3-yIy (y = 0, 1, 2) reveals that these materials exhibit semiconducting behavior at normal pressure. The energy gap of CsPbF3 is tuned by substituting iodine atoms for fluorine atoms. The optical parameters, such as dielectric function, electron energy loss function, refractive index and reflectivity, are computed. The optical properties of these lead-based halide perovskites against the incident photon energy radiation indicate that these materials can be effective candidates for the solar cell applications. [ABSTRACT FROM AUTHOR]

The halide perovskites are attractive for solar cells due to their excellent power conversion efficiency and low cost. The structural properties of Sn-based halide perovskites CsSnI3−y Fy (y = 0, 1, 2, 3) are investigated using first-principles calculation based on density functional theory. The computed electronic structure profile reveals that these materials exhibit semiconducting behavior. The energy gap value of CsSnI3 is tuned by substituting fluorine atom for iodine atom. It is observed that when the halogen atom fluorine is substituted for iodine atom in CsSnI3, the energy gap values are changed. As the pressure is increased, the energy gap value of these materials decreases and at high pressure, a semiconductor to metallic transition is observed. The optical properties of these Sn-based compounds indicate that these materials may be the effective candidates for the solar cell applications. [ABSTRACT FROM AUTHOR]

Lead-based halide perovskites are attractive substrates for solar cells because of their excellent power conversion efficiency and low cost. The ground-state properties, electronic structure, as well as optical and phonon properties of lead-based halide perovskites (CsPbCl3−yIy (y = 0, 1, 2, 3) are investigated by first-principles calculations based on density functional theory. Their electronic structure indicates that CsPbCl3−y Iy (y = 0, 1, 2, 3) compounds exhibit semiconducting behaviour at normal pressure. The energy gap of CsPbCl3 can be tuned by substituting iodine atoms for chlorine atoms. The energy gap values are found to be 3.06, 2.681, 2.330, and 2.030 eV using HSE06 calculations for CsPbCl3, CsPbCl2I, CsPbClI2, and CsPbI3, respectively. Also, it is found that the energy gap values of these materials decrease with increase in pressure and that a semiconductor-to-metallic phase transition is observed at high pressure. The optical properties of these Pb-based compounds are analysed. The dynamical stability of these perovskites is analysed by their phonon dispersion curves. [ABSTRACT FROM AUTHOR]

The first principles calculations are carried out to understand the half metallic and ferromagnetic properties of Fe2−xCoxTiSi (x = 0, 0.5, 1, 1.5, 2) full Heusler alloys. The stable structure is predicted as L21 structure (Cu2MnAl phase). The lattice constant value of Fe2−xCoxTiSi Heusler compounds increases as the value of x increases. These alloys exhibit half metallic ferromagnetism (except Fe2TiSi) with small spin flip gap at the minority spin state. At high pressure, semiconductor to metallic phase transition is observed in Fe2TiSi while half metallic to metallic phase transition is observed in Fe1.5Co0.5TiSi, Fe1.0 Co1.0TiSi, Fe0.5Co1.5TiSi and Co2TiSi. The spin polarization of these compounds (except Fe2TiSi) is 100%. Hence, these compounds are suitable for spin injection devices in spintronics. [ABSTRACT FROM AUTHOR]

The half-metallic and ferromagnetic properties of Co2TiZ (Z = Al, Ga, In) Heusler alloys are investigated. The structural stability is analyzed among the two possible structures, namely, L21 (Cu2MnAl phase) and XA (Hg2CuTi phase) structures. It is found that these alloys are stable in L21 (Cu2MnAl phase) structure. The electronic structure of Co2TiZ reveals that these alloys exhibit half-metallic ferromagnetism with small spin-flip gap at the minority spin state. As the pressure is increased, ferromagnetic to non-magnetic phase transition is observed at the pressures of 380.9, 363.0 and 317.8 GPa for Co2TiAl, Co2TiGa and Co2TiIn, respectively. Half-metallic to metallic phase transition occurs in Co2TiAl, Co2TiGa and Co2TiIn at the pressures of 76.5 GPa, 73.1 GPa and 63.9 GPa respectively. [ABSTRACT FROM AUTHOR]

The electronic structure of silicon carbide with increasing germanium content have been examined using first principles calculations based on density functional theory. The structural stability is analysed between two different phases, namely, cubic zinc blende and hexagonal phases. The zinc blende structure is found to be the stable one for all the Si1-xGexC semiconducting carbides at normal pressure. Effect of substitution of Ge for Si in SiC on electronic and mechanical properties is studied. It is observed that cubic SiC is a semiconductor with the band gap value 1.243 eV. The band gap value of SiC is increased due to the substitution of Ge and the band gap values of Si 0.75 Ge 0.25 C, Si 0.50 Ge 0.50 C, Si 0.25 Ge 0.75 C and GeC are 1.322 eV, 1.413 eV, 1.574 eV and 1.657 eV respectively. As the pressure is increased, it is found that the energy gap gets decreased for Si1-x GexC (X = 0, 0.25, 0.50, 0.75, 1). The elastic constants satisfy the Born - Huang elastic stability criteria. The bulk modulus, shear modulus, Young's modulus and Poisson's ratio are also calculated and compared with the other available results. [ABSTRACT FROM AUTHOR]

Halide perovskite-based solar cells are attractive due to their excellent power conversion efficiency and low cost. Sn-based halide perovskites CsSnI3−yCly (y = 0, 1, 2, 3) are investigated in this work using first-principles calculations based on density functional theory. The computed electronic structure profile reveals that these materials exhibit semiconducting behavior. The energy gap value of CsSnI3 is tuned by substituting Cl atom for iodine atom. As the pressure is increased, the energy gap value of these materials decreases, and a semiconductor to metallic transition is observed at high pressure. The optical properties of these Sn-based compounds, including the real and imaginary parts of the dielectric function, electron energy loss function, refractive index, and reflectivity, are computed. The dynamical stability of these perovskites is analyzed based on the phonon dispersion curve. [ABSTRACT FROM AUTHOR]