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Tetrahedrite, Cu12Sb4S13, an eco-friendly thermoelectric material with earth-abundant and low-cost constituents, has garnered global interest. This study investigated the thermoelectric characteristics of Ag-added tetrahedrites, which were prepared through solid-state synthesis and subsequently hot-pressed. The minimal temperature dependence of the transport coefficient indicated the presence of strong electron–phonon coupling in the samples. It was observed that Ag addition in tetrahedrite could successfully scatter acoustic phonons, reducing the lattice thermal conductivity while minimally affecting the power factor. The enhanced anharmonicity induced by Ag addition is the primary cause of reduced lattice thermal conductivity. Raman spectroscopy data showed that Ag addition could weaken the Sb–S bond, further supporting the previous argument. Consequently, the lattice thermal conductivity was lowered to ∼0.27 W m−1 K−1 and obtained for the composition Ag0.025 added Cu11.975Sb4S13. A relatively high power factor of ∼1.3 mW m−1 K−2 was obtained for the same composition. Owing to the lowest total thermal conductivity ∼1.09 W m−1 K−1, the sample with composition Ag0.025 added Cu11.975Sb4S13 showed the highest thermoelectric figure of merit of 0.87 at 738 K. [ABSTRACT FROM AUTHOR]

The compound Cu12Sb4S13, known as tetrahedrite, is an eco-friendly p-type thermoelectric material with earth-abundant, low-cost, and less toxic constituents. This contemporary work studied the thermoelectric properties of Gd and Se double-substituted tetrahedrites. The samples with nominal composition Cu11.95Gd0.05Sb4S13−xSex (where x = 0, 0.2, 0.4, 0.6, and 0.8) were prepared using the solid-state synthesis and sintered using high vacuum hot pressing. The structural analysis using X-ray diffraction revealed a successful tetrahedrite phase formation, and the systematic increase of lattice parameters with the selenium content (x) indicated successful Se substitution. The electron probe microanalysis revealed the presence of secondary phases Cu3SbS4, CuSbS2, and CuGdS2. The Raman spectroscopy showed a weakening Sb–S/Se bond with increased Se content in the samples. The +3 and −2 oxidation states of Gd and Se, respectively, were confirmed from the XPS study. Gd3+, a higher valence substituent at the Cu+/Cu2+ tetrahedral site, helped reduce the carrier concentration. On the other hand, the isoelectronic substitution of Se2− for S2− enhanced the thermopower and power factor by introducing resonant energy states near the Fermi level. Consequently, a maximum power factor of ∼1.35 (±0.08) mW m−1 K−2 at ∼729 K was obtained for the sample x = 0.4. The sample x = 0.4 also exhibited the lowest thermal conductivity ∼ 1.18 (±0.04) W m−1 K−1 at 729 K. The Callaway model indicates that the lowering in the lattice thermal part of conductivity of this sample is due to the combined effect of point defect and Umklapp scattering. The simultaneous improvement of carrier concentration and thermal conductivity resulted in a relatively high zT of ∼0.83 (±0.09) in the x = 0.4 sample. [ABSTRACT FROM AUTHOR]

Uniform dispersion of nanosized secondary phases in bulk thermoelectric materials has proven to be an effective strategy to reduce the lattice part of thermal conductivity and improve the thermoelectric efficiency. In this work, reduced graphene oxide (rGO) was uniformly dispersed in the In0.5Co4Sb12 bulk material by ultrasonication. The formation of impurity phases of InSb and CoSb2 in the In-filled Co4Sb12 is inevitable, as observed from XRD and EPMA analyses. The Raman spectra of the nanocomposites showed broad peaks suggesting phonon softening and additional peaks corresponding to rGO. Electron transport was not affected by rGO addition, resulting in little change in the electrical resistivity and Seebeck coefficient. The lattice thermal conductivity of the bulk material was significantly reduced by the addition of a small amount of rGO, primarily attributed to the interface scattering of phonons. Hence, the highest zT of ∼1.53 at 773 K was achieved for the In0.5Co4Sb12/0.25 vol% rGO composite in the temperature range from 723 K to 773 K. [ABSTRACT FROM AUTHOR]

In this study, aluminum, a p-block element, is substituted at the Cu(1) site, and its effect on the structural and thermoelectric properties of tetrahedrite Cu12−xAlxSb4S13 (x = 0.1, 0.25, 0.5, and 0.75) was investigated. The samples were prepared via solid-state synthesis followed by induction hot pressing. The theoretical calculations, using density functional theory (DFT), showed that the Al substitution results in lowering the band degeneracy near the Fermi level (EF) with EF moving towards the bandgap, indicating effective compensation of holes. The projected density of states (PDOS) revealed almost negligible hybridization of Al states with Cu 3d and S 3p states near EF, thus resulting in relatively low DOS near EF. The electrical resistivity and Seebeck coefficient increased with increasing Al content due to the compensation of holes and reduction of the charge carrier concentration. However, the Seebeck coefficient values were relatively low due to a low DOS near EF, as indicated by the DFT calculations. Although the electronic thermal conductivity (κe) decreased with increasing Al concentration, the magnitudes of the total thermal conductivity (κT) could not be reduced significantly. As a result, a maximum zT of 0.6 at 673 K was obtained for Cu11.9Al0.1Sb4S13. Based on the current study and previously reported results, the paper demonstrates how the phase stability and transport properties of the tetrahedrite are affected significantly by the nature of the substituent at the Cu(1) tetrahedral site. [ABSTRACT FROM AUTHOR]

Perovskites have been one of the most promising futures of solar‐cell technology due to their revolutionary impact on device performance. Recently, perovskite solar cell (PSC) has shown remarkable achievement in power conversion efficiency of 26.1% in 2022 by the Ulsan National Institute of Science and Technology. However, such a breakthrough technology has limitations for the market‐up due to inherent instability affected by heat, light, and moisture, which are severe issues for overcoming the barrier to commercialization. Several important outcomes of the experimental and theoretical analysis of the fundamental of PSCs are begun with in this review. The main aim of this article is to gain insight into the several processing approaches such as the interfacial approach, device structure approach, deposition method–based approach, compositional approach, bandgap approach, and dimensional approach. Interestingly, these approaches govern the charge‐transport process, recombination, charge‐transfer resistance, carrier injection/collection of the electrodes, etc. Finally, future perspectives of the combined understanding of various aspects are discussed to further enhance the device's performance. [ABSTRACT FROM AUTHOR]

Ti2−xNiCoSnSb (x = 0.125, 0.250, 0.375, and 0.500) half Heusler (HH) high-entropy thermoelectric alloys were synthesized by the arc melting—ball milling—spark plasma sintering route. The impact of secondary phase content on the thermoelectric properties in these alloys was examined. Ni-rich intermetallic (Ni3Sn2, Ni3Sn4) compounds were observed; the intermetallic content increased for lower Ti content, e.g., Ti1.5NiCoSnSb. A Ni-rich full Heusler (FH) secondary phase was also observed. These results were consistent with first-principles calculations that show that the formation enthalpy of Ti1.5NiCoSnSb was higher than that of Ti2NiCoSnSb and the full Heusler (FH) TiNi2Sn phase. In lower Ti content samples, the electrical conductivity increased, and lattice thermal conductivity decreased at the expense of thermopower owing to higher FH and the Ni3Sn2 phase content. Ti1.5NiCoSnSb exhibited lower lattice thermal conductivity of 3.5 W/mK, compared to 5.4 W/mK at 823 K for Ti2NiCoSnSb due to increased phonon scattering at HH/Ni3Sn2 interfaces. But considering the decreasing power factor with lower Ti content, the maximum ZT obtained in Ti1.875NiCoSnSb (0.171 at 973 K) was only marginally higher than the value for Ti2NiCoSnSb. Further, compositional tuning is hence necessary to maximize the power factor. [ABSTRACT FROM AUTHOR]

The thermoelectric properties of bulk as well as thin films of Bi93Sb7, grown by vacuum flash evaporation technique, are analyzed. The scattering index parameter is calculated in both as-grown and annealed films and it is observed that both the electrical conductivity and thermoelectric power of annealed films are larger than those of as-grown films.