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The current investigation employs first‐principles DFT (density functional theory) calculations to examine the influence of transition metal replacements on the structural, thermodynamic, and thermoelectric properties of Cu‐based chalcogenides TMCu3Se4 (TM = Nb/Ta/V). The PBE‐generalized gradient approximation (GGA) model is utilized to compute the fundamental properties of Cu‐based chalcogenides under study. A thorough examination of the energy band structures indicates that these chalcogenides are semiconductor compounds with indirect energy bandgaps. We can infer from the calculated energy band structures that the bandgap values are 1.67, 1.77, and 1.05 eV for NbCu3Se4, TaCu3Se4, and VCu3Se4, respectively. The ZTe$$ {\mathrm{ZT}}_e $$ values for NbCu3Se4, TaCu3Se4, and VCu3Se4 are 0.661, 0.998, and 0.996, respectively. These values make them highly appropriate for usage in thermoelectric (TE) devices. The thermoelectric characteristics of pyrochlore oxides TMCu3Se4 (TM = Nb/Ta/V) suggest that these materials have promising potential for energy‐related applications. The analyzed thermodynamic properties demonstrate that the Cu0based chalcogenide materials TMCu3Se4 (TM = Nb/Ta/V) exhibit a notable level of thermal stability. [ABSTRACT FROM AUTHOR]

Lead‐free double perovskites are now assumed to be suitable candidates for green energy harvesting in particular as active materials for solar cells and thermoelectric generators, which can meet future generation energy needs. Therefore, we explore the Au‐based halide double perovskites X2Au+Au3+Br6 (X = Cs, Rb) from the first principles approach. Density functional theory (DFT) is utilized to explore the electronic structure with DFT code Quantum ESPRESSO. The mechanical, thermodynamic, and structural stability is ensured from Burn‐Haun criterion, formation energies, and Goldschmidt factors, respectively. The examined materials have stable structures with direct band gaps i.e. 1.54 and 1.72 eV. The existence of band gaps in the visible region motivates us to explore the optical properties, which give fascinating outcomes. The absorption coefficients and optical conductivity peaks are found to be significant in the visible region i.e., ≈104 cm−1 and ≈1015 s−1, respectively. Additionally, the thermoelectric properties are also investigated using Boltzmann transport theory. There are several good gestures for the usage in the thermoelectric generators since the values of Seebeck coefficients (446.5, and 225.2 μV K−1), power factors (1.75 × 1011 W mk−2 s, and 1.24 × 1011 W mk−2 s), and figure of merits (0.92 and 0.73) are noteworthy for Cs2AuAuBr6 and Rb2AuAuBr6, respectively, at room temperature T = 300 K. [ABSTRACT FROM AUTHOR]

[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]

[Display omitted] • Structural, optoelectronic, and thermophysical properties of Nb-based pyrochlore oxides A 2 Nb 2 O 7 (A = Ba, Mg and Sr) are investigated using ab-initio calculations. • A 2 Nb 2 O 7 (A = Ba, Mg and Sr) are narrow band semiconductors. • The ZT values for Mg2Nb2O7 [0.998] and Sr2Nb2O7 [0.996] make them favorite candidates for TE device applications. • Optical spectra show major absorption peaks for these pyrochlore oxides occur in near UV region. The present study employed first-principles DFT (density functional theory) computations to investigate the impact of alkaline metal substitutions on the structural, optoelectronic, thermodynamic, and thermoelectric characteristics of Nb-based pyrochlore oxides A 2 Nb 2 O 7 (A = Ba, Mg and Sr). The PBE-GGA model is employed to calculate the fundamental characteristics of Nb-based pyrochlore oxides. An in-depth analysis of the energy band structures reveals that these Nb-based pyrochlore oxides are semiconductor compounds of A 2 Nb 2 O 7 (A = Ba, Mg, and Sr) reveals that these Nb-based pyrochlore oxides are semiconductors. The energy bandgap values are around 0.6, 3.05, and 1.4 eV for Ba 2 Nb 2 O 7 , Mg 2 Nb 2 O 7 , and Sr 2 Nb 2 O 7 , respectively. Based on the observed ε 2 (ω) spectra, it is apparent that the A 2 Nb 2 O 7 (A = Ba, Mg, and Sr) compound, exhibits a significant absorption of incident photons in the near UV region (at approximately 5.0 eV). The calculated values of n (ω) are 1.71, 1.66 and 1.63 for Ba 2 Nb 2 O 7 , Mg 2 Nb 2 O 7 and Sr 2 Nb 2 O 7 , respectively. The values of ZT are 0.661, 0.998 and 0.996 for Ba 2 Nb 2 O 7 , Mg 2 Nb 2 O 7 and Sr 2 Nb 2 O 7 , respectively, which make them favourite for TE device applications. The optoelectronic and thermoelectric properties of Nb-based pyrochlore oxides A 2 Nb 2 O 7 (A = Ba, Mg, and Sr) indicate their potential as favorable contenders for energy-related applications. The elucidated thermodynamic properties reveal that the Nb-based pyrochlore oxides A 2 Nb 2 O 7 (A = Ba, Mg, and Sr) display a high degree of thermal stability. [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]

The first-principles based DFT calculations were used to investigate the effect of transition metal (TM) doping on structural, electronic, optical and thermoelectric properties of Sn 1-x A x Se (A = Au and Ag). The PBE-GGA approximation is used to calculate ground state properties of TM doped SnSe. These compounds show the presence of type-II intermediate band (IB) at Fermi level. A considerable energy bandgap is present between IB and conduction band. Significant contributions from Ag/Au and Se-atom in valence bands of Sn 1-x A x Se (A = Au and Ag) are evident from presented DOS spectra. The calculated Fermi surfaces and Seebeck coefficient (S) confirms p-type nature of these semiconductors. From ε 2 (ω) spectra, it is evident that Sn 1-x A x Se (A = Au and Ag) absorbs maximum number of incident photons in infrared (at ∼0.5 eV) and visible (at ∼2.2 eV) regions. The calculated values of n (ω) are 2.27 and 2.58 for Sn 1-x Ag x Se and Sn 1-x Au x Se, respectively. We can confirm that Sn 1-x A x Se (A = Au and Ag) are promising candidates for energy applications (especially solar cells) based on their optoelectronic and thermoelectric properties. [Display omitted] • Electronic, optical and thermoelectric properties of Sn 1-x A x Se (A = Ag and Au) are investigated ab-initio. • Sn 1-x A x Se (A = Ag and Au) show type-II intermediate band in their band structures. • These compounds are p-type materials based on Fermi surface and Seebeck coefficient. • Optical spectra show major absorption peaks in visible region around 2.2 eV. • Among the considered compounds, Sn 1-x Au x Se shows the highest absorption. [ABSTRACT FROM AUTHOR]