Density Functional Theory Guided Solar Cell Capacitance Simulator‐1D Simulations of Lead‐Free ASnBr 3 (A = Li, Na, K, Rb, Cs) Perovskite Solar Cell

Decoupling the effects of defects on efficiency and stability through phosphonates in stable halide perovskite solar cells

We have carried out electronic structure calculations on N interstitials in GaAs alloys using the first-principles plane-wave pseudopotential (PWPP) and projector augmented-wave (PAW) electronic structure methods in the framework of the density functional theory (DFT). Both the ultrasoft pseudopotential (USPP) method in connection with the generalized gradient approximation (GGA) and the PAW method in connection with the local density approximation (LDA) have been employed. Effects of the single nitrogen atom and nitrogen dimer related interstitial defects on the atomic and electronic structures of GaAs have been studied. Total energies, electronic band structures, and local densities of states have been evaluated. In general, energies of the defects with the NN dimer at the center of the Ga or As tetrahedron are more than 2 eV lower per nitrogen atom than those with a single N impurity at the same sites. We have also found that there are metastable defect candidates with a single N impurity in the middle of a particular edge of the Ga or As tetrahedra. Considering the modifications of the atomic structure of GaAs, our calculations show that the relaxations of the nearest neighbor atoms around the NN dimer at the center of the Ga or As tetrahedron, are essentially smaller than those around the single N impurity at the center of an edge of the Ga tetrahedron. Finally, these defect states induce drastic modifications into the electronic structure of GaAs. Interestingly, the NN dimer related defects cause noticeable changes only to the conduction bands near the conduction band edge, while the single N impurity related defects mainly modify the valence band edge and also induce localized and delocalized states into the band gap. Notably, the NN dimer and N impurity related defects lead to redshift and blueshift behavior of the band gap, respectively. The blueshift behavior is tentatively supported by the recent photoluminescence experiments.

Lead-free tin perovskite solar cells

Revealing fundamentals of charge extraction in photovoltaic devices through potentiostatic photoluminescence imaging

The main impediment to practical application is the toxicity of lead ions in halide perovskite absorbing materials. Computing tools based on density functional theory (DFT) were used to predict the intrinsic properties of potential for double perovskites to be effective and suitable for optoelectronic applications, replacing the conventional lead halide perovskites with environmentally friendly elements. The Generalized Gradient Approximation (GGA) with Perdew-Burke-Ernzerhof (PBE) functional was used to screen homovalent alternatives for B and X-site ions in vacancy-ordered double perovskite Cs2BX6 (B=Pt, Ni, X= Cl, Br) for solar cell applications. Using the GGA with PBE functional, the band gap was calculated to be 1.411 eV, 0.482 eV, and 0.378 eV for the Cs2PtBr6, Cs2NiCl6, and Cs2NiBr6, respectively. The experimental band gap value of mother crystal's (Cs2PtBr6) was at 1.42 eV. Next, the DOS, PDOS and optical properties were computed using GGA with PBE functional. Then, the local density approximation (LDA) with Ceperley and Alder with Perdew and Zunger (CA-PZ) was executed to compare the GGA with PBE for electronic band structure. In addition, the OTFG ultra soft, OTFG norm conserving, ultra soft and norm conserving methods of pseudopotential were used for both GGA with PBE and LDA with CA-PZ to make and ensure the right or accurate DFT functional for those crystals. At last, the optical properties and their toxicity have been evaluated for their rational design of potential double perovskite materials with improved optoelectronic properties.

The spin effects on electronic, optical and mechanical properties of new ferromagnetic chalcopyrite: YMnS2

Perovskite materials have attracted research because of their ability to transition from normal metals to superconductors. This study reports the electronic structure and dynamical properties of LaBa2Cu3O7 perovskite carried out in the framework of density functional theory (DFT) using the Quantum espresso code. This is based on plane wave self-consistent field (PWscf) and ultrasoft pseudopotential (USPP) method as treated in the Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation and local density approximations as implemented in Quantum Espresso Code. The electronic structure uncovers essential aspects such as bandgaps, Fermi surfaces, and density of states, offering valuable insights into the material's behavior. Under structural properties, optimization of the material’s cell dimensions, lattice parameters, k-points, and the kinetic energy cut-off values was properly checked through graphing. Accurate values were obtained at the convergence of the ground state energy at a minimum convergence threshold. Band structures of LaBa2Cu3O7 are similar to that of superconducting perovskites. The results show that LaBa2Cu3O7 is an orthorhombic structure with lattice parameter calculated to be 3.925 Å which compares well with other works and a band gap of 2.043eV. O 2p states typically dominate the valence band, while the conduction band involves Cu 3d states. Phonon calculations shows that the compound is dynamically stable as there are no negative frequencies observed.

Photovoltaics literature survey (No. 181)

Thermoelastic parameter αKT of sodium chloride at high pressure and high temperature

DFT investigation of elastic, mechanical, vibrational and thermodynamic properties of cadmium dichalcogenides

BaTiO3 perovskite for optoelectronics application: A DFT study

The electronic, mechanical and thermodynamic properties of XO ( \( {\rm X}= {\rm Am}\) , Cd, Mg, and Zr) compounds are studied by performing density functional theory (DFT) calculations. We have calculated the elastic constant, various moduli, phonon dispersion relation, and density of phonon state, heat capacity, density of state, electronic band structure, Debye temperature, free energy and enthalpy of the compounds. For this goal, we have performed our calculations within local density approximation (LDA) functional with ultra-soft pseudopotentials (USP) and generalized gradient approximation (GGA). According to the obtained results, it is found that i) CdO and ZrO compounds are ductile and MgO is a brittle material; ii) ZrO is less stable against shear forces than MgO and CdO; iii) at high temperatures, the heat capacity and Debye temperature approach a constant value for all compounds; iv) at temperatures higher than 60K, the averaged sound velocity in CdO is higher than MgO and ZrO; v) the ZrO and CdO are treated properly using GGA.

Copper(I)-Based Highly Emissive All-Inorganic Rare-Earth Halide Clusters

Ab initio density functional plane-wave calculations are performed to study the lattice constant, bulk modulus, and the pressure derivative of the bulk modulus of ternary zincblende AlInN. Results obtained using local density approximation (LDA) and generalized gradient approximation (GGA) for the exchange-correlation energy are investigated and compared with available binary experimental results. For AlN it is found that GGA provides a better agreement with experiment than LDA one does. For InN LDA appears to perform better. The deviation parameter of bulk modulus of zincblende Al_xIn_1-xN is 10.34 ± 9.27 GPa using LDA and 18.48 ± 2.28 GPa using GGA.

Strontium fluoride (SrF2) is an important member of alkaline-earth fluorides for its intrinsic optical properties and superionic application at animated temperatures as well as thermoluminescent behavior. Using abinitio density functional theory (DFT) method and density functional perturbation theory (DFPT), the structural, phonon frequencies, optical properties and dielectric constants has been investigated. The calculations had been done using a first principle code Quantum espresso, implemented ultra-soft pseudo-potentials (US-PPs) and projector augmented wave (PAW) data sets with the local density approximation (LDA) and the generalized gradient approximation (GGA) for the exchange correlation. All pseudo-potentials showed results in a good agreement with other theoretical and experimental data.