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[Display omitted] • New energy harvesting mechanisms as alternatives for traditional energy sources. • Optoelectronics and thermoelectricity have gained much attention. • The future of thermoelectric generators. • High figure of merit promising for thermoelectric applications. Researchers have shown substantial interest in vacancy-ordered halide perovskites for non-traditional energy harvesting applications including solar cells and thermoelectric generators. In this study we performed band gap engineering of vacancy-ordered halide perovskite Cs 2 SnCl 6 from substitutional doping of Pt (Cs 2 Sn (1-x) Pt x Cl 6 where x = 0, 0.25, 0.50, 0.75 and 1.00) and studied its effects on thermoelectric properties using first-principles approach. Thermodynamic stability has been proven by computing the formation energies and the tolerance factors. The band gaps were efficiently reduced to 2.50 eV from 3.61 eV by the band gap engineering approach of Pt doping. Consequently, the materials exhibited improved thermoelectric properties, including low thermal conductivities, high Seebeck coefficients, and high values of ZT. The maximum value of ZT = 2.27 was estimated for x = 1.00. The Pt doping technique can be deemed effective based on the enhanced structural and thermoelectric performance parameters. [ABSTRACT FROM AUTHOR]

[Display omitted] • New energy harvesting mechanisms as alternatives for traditional energy sources. • Solar and thermoelectric energy sources have gained much attention. • The future of Perovskite Solar cells and other relevant optoelectronic applications. • High figure of merits promising for thermoelectric applications. A thorough comparative study of lead free zirconate perovskite XZrO 3 (X = Ca, Sr, Ba) is carried out employing WIEN2k which is a density functional theory based code. A good agreement between reported synthesis and the theoretical results is observed. BaZrO 3 can be inferred as the most stable compound among XZrO 3 (X = Ca, Sr, Ba) as its ground state energy is lowest. According to the Burn-Haun criterion, the compounds under research are mechanically stable. The ductile nature, anisotropy, and reasonable resistance to deformation in response to external stress are observed. The semiconducting nature of the compounds is observed having indirect band gaps with values of 3.25 eV, 3.71 eV, and 3.80 eV. Exceptional optical absorption peaks for the investigated compounds can be observed in UV region (around 5.0 eV) which suggests their numerous optoelectronic applications within UV. XZrO 3 (X = Ca, Sr, Ba) are active optical materials as their refractive inrdex n (ω) occurs in the range of 1.0 and 2.0. Thermoelectric properties of these compounds are also very promising since the large Seebeck coefficients (∼2250–2700 μV/K), large power factor values (∼1011 W/mK2s), and figure of merits are very close to the unity are observed. The mechanical stability and ductility, and the appealing optical and thermoelectric properties of the examined compounds persuade us that these compounds may play a significant role for numerous industrial applications like solar cells, LEDs, sensors, thermoelectric generators and other energy conversion devices in the future. [ABSTRACT FROM AUTHOR]

Vacancy-ordered halide perovskites have gained considerable attention from researchers regarding non-traditional energy harvesting applications like solar cells and thermoelectric generators. However, in most of the reported cases, band gaps are larger (>3.5eV) consequently the efficiency of solar cells and thermoelectric generators becomes low. Currently, we studied non-toxic and stable vacancy-ordered halide perovskites Cs 2 GeCl 6 and tuned its band gap via substitutional doping of Pt (0, 25, 50, 75, and 100 %) using the first-principles approach. The band gap engineering strategy of Pt doping effectively decreased the band gaps (up to 2.50eV) hence, the more attractive optical and thermoelectric parameters are obtained for instance; high absorption coefficients (∼105 cm−1), low reflectivity (∼0.3–10 %), high optical conductivity (∼1015 sec−1), and large figure of merits (∼1). Based on these enhanced optical and thermoelectric performance parameters, the Pt doping strategy can be taken as an effective practice to tune the band gap significantly in order to stimulate the performance of future solar cells and thermoelectric generators. • New energy harvesting mechanisms as alternatives for traditional energy sources. • Optoelectronics and thermoelectricity have gained much attention. • The future of Perovskite thermoelectric generators. • High absorption coefficient double perovskite with reasonable band gaps. • High figure of merit promising for thermoelectric applications. [ABSTRACT FROM AUTHOR]

• New energy harvesting mechanisms as alternatives for traditional energy sources. • Solar and thermoelectric energy sources have gained much attention. • The future of Perovskite Solar cells. • High absorption coefficient thallium based double perovskites with novel small band gaps. • High figure of merits promising for thermoelectric applications. Researchers have addressed the non-traditional power generation schemes, as alternatives to the traditional fossil-fuel methods enormously, since the scientific community has serious concerns about shortages of energy on our planet for future generations. In this scenario, innovative materials for photovoltaic and thermoelectric device applications are required by addressing current issues of instability and efficiency. Perovskites are very popular in this regard particularly having higher power conversion efficiency of 25.2% in the case of solar cells. In the current article, we investigated innovative small direct band gap double perovskites (elapsolite) Cs 2 AgTlX 6 (X = Cl, Br) with a comprehensive discussion on structural, electronic, optical, and thermoelectric properties using a first-principles approach. The compounds under investigation are found stable, efficient, and economical with alluring optical and thermoelectric properties. The higher absorption peaks in the visible range, substantial optical conductivities (∼1016sec-1), and a lower percentage of reflection in the visible range makes these compounds fascinating for solar cell applications. Whereas large values of Seebeck coefficients, electrical conductivities, the figure of merits (greater than unity), and small values of thermal conductivities suggest the applications of these compounds in thermoelectric generators. [ABSTRACT FROM AUTHOR]

Robust and Eco-friendly double perovskites X 2 AgFeBr 6 (X=Na, Li) simulations and exploration in terms of thermoelectric aspects. [Display omitted] • New energy harvesting mechanisms as alternatives for traditional energy sources. • Stable, Efficient, and Eco-friendly double perovskites. • Thermoelectric energy sources have gained much attention. • High figure of merits promising for thermoelectric applications. In this computational work, we simulated the robust and eco-friendly double perovskites X 2 AgFeBr 6 (X = Na, Li) for the first time in detail for green energy harvesting applications involving thermoelectric generators. The structural, mechanical, and thermodynamic stability is assured from the Goldschmidt's tolerance and octahedral parameters, Burn-Haun criterion, formation energies, and phonon spectra respectively. The electronic band structures and density of states informed us the semiconducting nature of the compounds with band gaps of 4.81 eV, and 3.82 eV. The thermoelectric parameters like electrical conductivity close to ∼ 1017(Ωms)-1, Seebeck coefficients up to 531.56 (μV/K), power factor in range of ∼ 1010 W/msk2, and figure of merits close to one are observed at room temperature (T = 300 K). These fascinating results provide a theoretical basis for the synthesis of lead-free double perovskites X 2 AgFeBr 6 (X = Na, Li), which find applications in thermoelectric devices. [ABSTRACT FROM AUTHOR]