Production of energy and its storage has become the main concern at the present time. Global environmental issues and the rising demand for a powering system of portable electronic devices as well as zero gaseous emission vehicles triggers research towards high energy and high voltage systems. Although Liion batteries have conquered the portable electronic market, yet its limited availability, high cost and safety issues have led to the search its alternatives. Na-ion and K-ion batteries may turn out to be a promising candidate for storage devices as they are cheaper and have higher energy density as compared to Li metals. We have proposed a fundamental theoretical design based on cubic double antiperovskite structure X 6 SOA 2 (X = Na, K; A = Cl, Br and I) by fullpotential augmented plane wave (FP-LAPW) method as implemented in the WIEN2k code within the density functional theory (DFT). We have calculated structural, electronic, optical, elastic, and thermodynamic properties and may be concluded that these materials are mechanically, dynamically, and thermally stable and have profound characteristics in high UV energy range. As these double antiperovskites have been studied for the very first time, this study may unfold a new vista for more comprehensive experimental and theoretical investigations for the search for non-toxic, eco-friendly and cheaper energy storage devices.

Minimal cost, huge area, high throughput, high performance of photovoltaic panels, prolonged lifespan, and less toxicity are vital aspects when transitioning photovoltaic technology from lab‐scale production to industrial implementations. A new class of materials typically known as hybrid halide double perovskites (HHDPs) has emerged as a possible alternative for the replacement of toxic lead in crystal lattice for realizing lead‐free, stable, and high‐performance perovskite solar cells (PSCs). An ab initio analysis of (MA)2AgInBr6 HHDP via the WIEN2K code is conducted. It is found that this material has a direct bandgap of 3.85 eV having excellent optical properties in the UV region. The calculated thermodynamic parameters confirm its thermal stability at different temperatures and pressure. Its figure of merit is more than unity at room temperature as well as higher temperature ranges, so this material will be useful in thermoelectric (TE) devices as a TE material.

In the present work, we have studied structural, electronic, optical and thermoelectric properties of Rb based state-of-the-art materials RbYZ (Y=Be, Mg, Ca, Sr and Ba; Z=P, As, Sb and Bi) having 8 valence electron count (VEC) using density functional theory followed by solution of Boltzmann transport equation with constant relaxation time approximation. The exchange and correlation potential are described by the GGA of Wu and Cohen (GGA-WC); the Becke-Johnson approach modified by Tran and Blaha (TB-mBJ) has been used to model the exchange-correlation potential. The bandgap of these materials lies in the range of 0.201 eV-2.591 eV. The various optical parameters are comparable with the state-of-the-art photovoltaic materials. Thermoelectric properties have been computed at 300 K, 600 K and 900 K. At these temperatures lattice thermal conductivity have been computed using Slack's model. This detailed study shows that these compounds are promising for renewable energy applications.

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We have explored the structural, electronic and transport parameters of cubic double antiperovskite structure X6SOA2 (X = Na, K and A = Cl, Br, I) using density functional theory followed by the solution of Boltzmann transport equation with constant relaxation time approximation. The exchange and correlation potential are described by the PBE‐GGA; the Becke‐Johnson approach modified by Tran and Blaha (TB‐mBJ) has been used to model the exchange‐correlation potential. Band gap of these materials have been found in between 2.85–4.24 eV. Thermoelectric properties have been computed at 300, 600 and 900 K. It has been found that figure of merit of double antiperovskite materials approaches to unity in both n‐ and p‐type regions. Hence these materials may turn out to be potential thermoelectric candidates. As these properties of the titled compounds have been explored for the very first time, hence, this work may open a new panorama for various detailed experimental and theoretical studies in the quest for non‐toxic, environmentally safe, and efficient energy sources.

Full potential‐linear augmented plane wave method with two exchange‐correlation potentials Perdew–Burke–Ernzerhof‐generalized gradient approximation and Becke–Johnson have been used to investigate structural, electronic, optical, transport and mechanical anisotropy of formamidinium lead halides (FAPbX3; X = Br, Cl). This computational exploration shows that these materials have a direct band gap, high absorption coefficients and the stability of the compound has been tested using the enthalpy of formation, and elastic stability criteria of the elastic constants. The persistent hybridization of s states of Pb and p states of Br/Cl in valence band contribute significantly in the structural stability. The calculated band gap is 2.26/2.84 eV for FAPbBr3 /FAPbCl3 and are in concurrence with the experimental and other theoretical studies. As higher absorption promotes higher emissions, optical properties with the peaks of dielectric function spectra with high energy region, and higher absorption peaks show the significant future for these materials to be used in color light‐emitting diode. Parameters of elastic properties like Bulk modulus, Young's modulus, Pugh's ratio and Poisson's ratio show that these have ductile nature and may be deposited as thin films, which is a significant feature in photovoltaic applications. Moreover, electronic transport properties have been calculated within the constant relaxation time approximation. This provided following observations: (a) Seebeck coefficient are noted to decrease with increasing temperature, (b) electrical conductivity are nearly constant within the whole temperature range, (c) thermal conductivity increased with increasing temperature, and (d) power factor and figure of merits are increasing with increasing temperature, and at a given electron and hole concentration (1018–1019 cm−3). The figure of merit signifies that these materials may also be used as thermoelectric devices. These computational observations hereby are of paramount importance for future integrated applications.

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