Value Of Seebeck Coefficient Research Articles

A computational study of novel CsYMSe3 (M = Cd, Zn) materials: for their potential optoelectronic and thermoelectric application

Abstract The thermoelectric performance and adjustable optical properties of chalcogenides are noteworthy. Density functional theory is employed to study the electrical, optical, and thermoelectric properties of the novel CsYMSe3 (M = Cd, Zn) quaternary chalcogenides. A direct band gap nature was predicted based on the band profile study. Using Perdew–Burke–Ernzerhof generalized gradient approximation and TB-modified Becke–Johnson, the reported band gaps are 2.12 and 2.92 eV for CsYZnSe3 and 2.11 and 3.07 eV for CsYCdSe3, respectively. The results showed that in both materials, the hybridization of the orbital Cs–p/d and the Se–p were responsible for direct energy losses. The complex dielectric function and the important linear optical parameters were investigated for possible usage in optoelectronic devices. These materials exhibit stronger absorption of photons. These materials could be employed as particularly effective UV-reflecting materials from the noticed peaks in the reflectivity spectra. Because of their negative Seebeck coefficient values, both materials show n-type conductivity across the whole temperature range. CsYZnSe3 possesses better electrical conductivity than CsYCdSe3, which results in a larger ZT value.

Coexistence of Kondo effect and non trivial Berry phase in Gd doped Bi2Se3: an ARPES and magneto-transport study

Abstract The presence of magnetic impurities in Topological Insulators (TI) can disrupt their Time Reversal Symmetry (TRS) and lead to the emergence of an energy gap. This study delves into the energy band structure and the Kondo effect through the introduction of Gadolinium(Gd) magnetic perturbations (at levels of x = 0.1, 0.16) into a pure Bi2Se3 single crystal. In the case of the Bi1.9Gd0.1Se3 (5%) single crystal, the Kondo effect becomes observable at temperatures below 50K. However, the unaltered parent and Bi1.84Gd0.16Se3 (8%) exhibit typical metallic behavior. The pure sample displays the highest magnetoresistance (MR) of around 225% and demonstrates quantum oscillations driven by a nontrivial berry phase. The sample doped with 5% Gd undergoes a transition from negative magnetoresistance (NMR) to positive magnetoresistance (PMR) due to a presence of mixed magnetic state resulting from the opening of a gap at the Dirac point. This gap opening is confirmed through Angle-Resolved Photoemission Spectroscopy (ARPES) measurements. Thermoelectric properties are assessed across all prepared samples. The undoped sample displays the highest Seebeck coefficient and power factor (PF) values of -398.02 µV/K and 6.83 mW/mK2, respectively, at room temperature. These values are notably high for thermoelectric applications at room temperature.

Insight into the optoelectronic and thermoelectric properties of novel LaSeM (M = Cl, F) chalcohalide semiconductors: ab-initio study

Abstract Chalcohalide materials demonstrate extraordinary thermal capacity and adjustable optoelectronic properties. Here we used the density functional theory and studied the structural, electronic, optical, and thermoelectric properties of novel LaSeM (M = Cl, F) ternary chalcohalides. The formation energies of LaSeCl and LaSeF were determined to be −2.21 (eV/f. u) and −2.32 (eV/f. u), respectively. The cohesive and formation energies well impacted the stable nature and phase transition features of these materials. The studeid materials were predicted to have a direct band gap nature as observed from the band structure investigation. For LaSeCl material, the projected band gaps as determined by the PBE-GGA and TB-mBJ potentials are 1.41 eV and 1.95 eV, whereas for the LaSeF the values are 1.72 eV and 2.36 eV, respectively. The complex dielectric function along with the other noteworthy optical parameters are computed for their potential applications in optoelectronics devices. The spectral region with a negative value of ε 1(ω), suggests these materials to have a metallic behavior. The predicted negative Seebeck coefficient values throughout the temperature range for LaSeCl and LaSeF materials display n-type conduction behavior. LaSeF exhibits more noticeable temperature-dependent improvements in electrical conductivity compared to LaSeCl.

Complex Structure, Chemical Bonding, and Electrical Transport Properties of a La-Doped Zintl Phase

The La-doped ternary Zintl phase Ca10.43(3)La0.57Sb9.69(1) was successfully synthesized by arc melting, and the title compound adopted the Ho11Ge10-type structure with a tetragonal I4/mmm space group (Z = 4, Pearson code tI84). The complex crystal structure is composed of (1) the four different kinds of cationic Ca or Ca/La mixed sites surrounded by seven or nine Sb atoms and (2) the 3-dimensional cage-shaped anionic frameworks built by the other two types of Sb atoms. In particular, the La dopants preferred to occupy the Ca4 and Ca1 sites, and this specific cationic-site preference can be rationalized by both electronic and size-factor criteria. Moreover, the ca. 16% occupational deficiency observed at the Sb3 site was attributed to the energetically unfavorable antibonding character of the Sb3–Sb3 bond in the [Sb3]4 tetramers, according to a series of DFT calculations. A crystal Hamilton overlap population curve analysis also proved that the title compound Ca10.43(3)La0.57Sb9.69(1) tried to keep the valence electron count below 71.02 to remain energetically stable in the Ho11Ge10-type phase. Measurements of temperature-dependent electrical transport properties revealed that the La doping indeed enhanced the electrical conductivity of Ca10.43(3)La0.57Sb9.69(1) compared to the un-doped Ca11Sb10. However, unlike other rare earth metal (RE)-doped compounds in the Ca11−xRExSb10 (RE = Nd and Sm) system that display semiconducting behavior, the La-doped title compound showed poor metallic electrical properties. The positive values of Seebeck coefficients indicated the p-type character of the title compound despite the successful n-type La doping, and this should be attributed to Sb deficiency.

Effects of Ti and Sn Substitutions on Magnetic and Transport Properties of the TiFe2Sn Full Heusler Compound

The synthesis of polycrystalline TiFe2Sn samples by a route including arc melting and spark plasma sintering with Hf, Y, and In substitutions at the Ti and Sn sites is investigated. For a reduced amount of substitution, around 2 at%, the samples are single phase, while for increased amounts, secondary phases segregate. As is characteristic of these compounds, the Fe-Ti atomic disorder generates a weak ferromagnetic ordering, which is also influenced by the type of substitutional atoms and the secondary phases in the samples with a higher Hf content. The Seebeck coefficient values show an increase for Ti0.98Hf0.02Fe2Sn and for samples with an adjusted Sn content, resulting in slightly increased power factor values. These values reach a maximum for Ti0.98Hf0.02Fe2Sn at approximately 300 K and for TiFe2Sn1.05 at approximately 325 K, namely, 2.69 × 10⁻4 Wm−1K−2 and 2.52 × 10⁻4 Wm−1K−2, respectively. The thermal conductivity of all the samples with substitutions increases with respect to the pristine sample. The highest figure of merit value of 0.016 is also obtained for Ti0.98Hf0.02Fe2Sn at 325 K.

Bi[Se‐(2‐Me2NC6H4)]3: Single Source Precursor for Preparing Pure‐Phase, 2‐Dimensional Bismuth Selenide Films

AbstractChemical vapor deposition using molecular compounds is a salient method to achieve high‐quality, uniform films comprising two‐dimensional flakes. In this communication, we present the synthesis and characterization of analytically pure single crystals of Bi[Se‐(2‐Me2NC6H4)]3, used as a single source precursor to grow thin films of bismuth selenide. The structural and morphological studies of the films were performed using powder X‐ray diffraction, Raman spectroscopy, scanning, and transmission electron microscopy, revealing a pure phase stoichiometry with two‐dimensional flakes of quintuple layers grown on glass, Si, and sapphire substrates. The deposited films on the glass surface show a near‐ideal Bi to Se stoichiometry of 1.84 and exhibit an ambient temperature resistivity of 30 mΩ.cm. When unevenly illuminated with a laser of 532 nm wavelength, it shows a photo‐thermoelectric (PTE) voltage generation with a response time of 2 seconds and an estimated Seebeck coefficient value of −128±6.6 μV/K, thus demonstrating its suitability for device applications in IoTs.

Electronic, thermoelectric and magnetic properties of ternary telluride KAlTe2 and KInTe2 from theoretical perspective

First principles study has been applied to the anisotropic ternary KAlTe2 and KInTe2 materials. The energy of each material is optimized to the ground level through WIEN2k code and results are compared with the available theoretical and experimental findings. It is obtained from our results that materials have direct band gap and the calculated band gaps for KAlTe2 and KInTe2 are 1.68 eV and 0.931 eV, respectively. The direct band semiconductors are important for thermoelectric and optical devices. Theoretically the material KAlTe2 is investigated paramagnetic while KInTe2 is diamagnetic after applying GGA. The calculated numerical values of magnetic behavior are small, which suggests the materials exhibit weak magnetism. The semi-classical Boltzmann technique implemented in the BoltzTraP package was used to determine thermoelectric properties including the seebeck coefficient, electrical conductivity, thermal conductivity, and figure of merit (ZT). The seebeck Coefficient value for KInTe2 in N-types region is –11.99 µV/K, the chemical potential range have taken between 0.00 eV to –0.02 eV for the P-type calculated value is material 11.96–8.08 µV/K. The maximum seebeck Coefficient values for the materials KAlTe2 in the N-type region is –0.35 and 0.57 µV/K and P-type region is 5.5–6.7 µV/K, respectively. Calculated numeric values of ZT for both materials are high and materials suited for N-type doping and keeping excellent thermoelectric materials for newly developed semiconductor devices.

First principles calculations of physical properties of the CeCu2Si2 material

Using local density approximation functional computations, LSDA (local spin density approximation) and mBJ (modified Becke-Johnson) for exchange-correlation interactions, we examined the combination CeCu2Si2, concentrating on its many physical properties. This work used the WC-GGA method to compute the elastic characteristics of CeCu2Si2 material, and the results indicate that unstrained CeCu2Si2 is more brittle. The density of states exhibits the metallic character of the chemical, in agreement with the inference made from the band structure. We also assessed several optical characteristics, such as real and imaginary optical conductivity, electronic energy loss, absorption coefficient, refractive index, and extinction coefficient. We also looked at the electronic components of thermal conductivity, electrical conductivity, Seebeck coefficient, and electronic conductivity. The compound's Seebeck coefficient values are negative, indicating p-type behavior. A thorough analysis of the data is presented, along with important details regarding the CeCu2Si2 compound's characteristics.

Study of Structural, Thermal and Electrical Properties of Sr-Doped CaMnO<sub>3</sub>

Sr-doped CaMnO3 materials have wide applications due to their thermal and electrical properties. The importance of the synthesis of Sr-doped CaMnO3 material for various applications encourages researchers to evaluate and refine the synthesis process. In this study, Ca1-xSrxMnO3 (x = 0; 0.05; 0.1; 0.15; 0.2) system has been prepared by sol-gel method followed by conventional sintering process at 850°C for 8 hr. A thorough discussion has been made on the outcomes derived from the investigation on the structural, electrical, and thermal properties of Sr-doped CaMnO3 system using powder x-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, DC fourprobe method, thermal expansion studies, and thermoelectric power analyses. The XRD patterns of all prepared samples exhibited single phase with orthorhombic crystal structure (space group Pnma). Rietveld refinements were performed for all the patterns by using Fullprof software to extract the structural properties. The values of unit cell volume of samples tend to increase with the increment of dopant concentration, whereas the crystallite size values were decreased with dopant concentration. The microstructures of all the samples were studied using SEM, and elemental compositions were confirmed from the EDS results. Linear thermal expansion coefficients of all the samples were found to have moderate values in the temperature range from 30°C to 800°C. The electrical properties of all the system of samples were studied in the temperature range from 30°C to 400°C using DC fourprobe conductivity setup. It was found that all the samples exhibited semiconductor nature. Sr-content on the A-site suppress the electrical resistivity up to 10% of concentration and 5% dopant content exhibited the lowest electrical resistivity. The values of Seebeck coefficient found to vary from -160 µV/K to -124 µV/K with the increase of dopant content in the parent compound.

Structural, Magnetic, and Transport Properties of Ti(Fe,Re)2Sn Heusler Alloys

This study investigates polycrystalline samples of TiFe2−xRexSn (with x = {0, 0.02, 0.04, 0.06, 0.2}) synthesized using conventional arc-melting and spark plasma sintering. Structural and morphological analysis shows that low Re substitutions result in good phase purity with minor traces of secondary phases, while higher Re content leads to the segregation of additional phases. The magnetism and electrical resistivity of the samples are affected by inherent Fe–Ti atomic disorder, with the effects of secondary phases becoming more prominent in the samples with higher Re content. The Seebeck coefficient values increase only for TiFe1.98Re0.02Sn, while the power factor increases for x = {0, 0.02, 0.04}, reaching maximal values for x = 0.02 at ~ 300 K and x = 0.04 at ~ 325 K, i.e., (2.22 ± 0.2) × 10−4 Wm−1 K−2. The thermal conductivity of the samples increases with x, resulting in modest values of the figure of merit, with the maximum achieved for x = 0.02 at 325 K, i.e., 0.015 ± 0.002.

Ab-initio investigation of structural, electronic, thermoelectric and optical properties of Full-Heusler X2MnB (X = Ti, Zr) for energy harvesting applications

In this manuscript comprehensive first-principles calculations have been presented for Full-Heusler X2MnB (X = Ti, Zr) compounds. This work includes detailed observations of the structural stability, origin of the transport phenomenon, optical properties, and electronic response. Structural parameters support the previous findings by confirming structural stability in the non-magnetic phase. Ti2MnB (Zr2MnB) valence band maxima and conduction band minima have bandgaps of 0.217 (0.301) eV and 0.181 (0.209) eV for PBE-GGA (mBJ) approximations which lie between L-L symmetry points. Due to the comparative measurements of the two states, the DOS results show that the Ti1/Zr1, Ti2/Zr2 Mn eg, and t2g states mainly contribute to the valence band region for Ti2MnB and Zr2MnB alloys, confirming their ionic nature. The computation of the overall electronic parameters’ reveals semiconducting nature. Thermoelectric properties have been calculated as a function of temperature in the 100–1200 K range. The positive values of Seebeck coefficients specify p-type character of X2MnB While at 300 K, Zr2MnB and Ti2MnB showed the highest Seebeck coefficients, measuring roughly values of 268 (µK/V) and 243 (µK/V), respectively. These values suggest that the material exhibits high thermoelectric performance. Though high optical absorption coefficient and low reflectivity in the visible and ultra violet regions, confirms use of these materials in solar cell applications. These findings suggest that material holds great potential for use in thermoelectrical applications which can support in upcoming experimental considerations.

Theoretical Studies of the Electronic and Thermoelectric Properties of PrIn3 and NdIn3 in Cubic Phase

The electronic and thermoelectric properties of AB3 (A =Pr, Nd and B=In) materials (crystallizing in the cubic structure) having space group Pm-3m (221) are studied using B3PW91 hybrid functional through the Full-Potential Linear Augmented Plane Wave (FP-LAPW) approach within the framework of Density Functional Theory (DFT). The calculated lattice parameters for PrIn3 and NdIn3 are 4.5668 Å and 4.5539 Å respectively. Electron-electron correlation effect is due to the 4f orbitals present in these materials and therefore, with the use of B3PW91 hybrid functional, band structure and density of states are calculated. When analyzing electron charge density, these materials showed a stronger ionic character. Band structure and density of state analysis confirms the metallic nature of the materials. Using the semi-empirical Boltzmann approach implemented in the BoltzTraP code, the thermoelectric parameters, such as Seebeck coefficient, figure of merit, electrical conductivity per relaxation time, and electronic thermal conductivity per relaxation time as a function of chemical potential, were computed at 500 K temperature gradient. PrIn3 showed highest Seebeck coefficient value, 50.68 μV/K among these compounds. The peak value of electrical conductivity per relaxation time and electronic thermal conductivity per relaxation time among these compounds is calculated for NdIn3 is 2.43 x 1020 1/Ωms and 22.50×1014 W/mKs.

Understanding the Anomalous Thermoelectric Behavior of Fe-V-W-Al-Based Thin Films.

We investigated the thermoelectric and thermal behavior of Fe-V-W-Al-based thin films prepared using the radio frequency magnetron sputtering technique at different oxygen pressures (0.1-1.0 × 10-2 Pa) and on different substrates (n, p, and undoped Si). Interestingly, at lower oxygen pressure, formation of a bcc-type Heusler structure was observed in deposited samples, whereas at higher oxygen pressure, we have noted the development of an amorphous structure in these samples. Our findings indicate that the moderately oxidized Fe-V-W-Al amorphous thin film deposited on the n-Si substrate possesses a large magnitude of S ∼ -1098 ± 100 μV K-1 near room temperature, which is almost double the previously reported value for thin films. Additionally, the power factor (PF) indicated an enormously large value of ∼33.9 mW m-1 K-2 near 320 K. The thermal conductivity of the amorphous thin film is also found to be 2.75 Wm-1 K-1, which is quite lower compared to bulk alloys. As a result, the maximum figure of merit is estimated to be extremely high, i.e., ∼3.9 near 320 K, which is among one of the highest reported values so far. The anomalously large value of Seebeck coefficient and PF has been ascribed to the unusual composite effect of the metallic amorphous oxide phase and insulating substrate possessing a large Seebeck coefficient.

Enhancing thermoelectric performance in flexible fabric-based Mo-doped CuAl2O4: Insights into carrier type modification and electrical conductivity optimization

In this work, we report the thermoelectric behaviour of flexible fabric-based Mo doped CuAl2O4. The doped Mo atom occupies the interstitial positions of the spinel lattice of CuAl2O4. This results the lattice expansion and also provides the carrier electrons. Initially, the pristine CuAl2O4 has the carrier concentration of 2.81 × 1014 cm−3, while doping with molybdenum, it not only increases the concentration of the carriers (about −7.65 × 1015 cm−3), but also changes the carrier type. The minimum doping (2 %) of molybdenum to spinel CuAl2O4 (CuAl2O4Mo0.02) creates the fermi level near to the conduction band, which reduces the band gap and results in the effective electrical conductivity as 0.69 Scm−1 at 340 K. The heavy doping enhances the scattering process. This leads to deduction of mobility and lower the electrical conductivity. The highest power factor of 0.0599 μWcm−1K−2 is achieved for the CuAl2O4Mo0.06 sample at 300 K. This is due to the high Seebeck coefficient value of the sample and has an ultralow thermal conductivity value of 0.056 W/mK. The highest output voltage of 3.9 mV is achieved for parallelly connected p-type CuAl2O4 -n-type CuAl2O4Mo0.02 thermoelectric device at the temperature difference of ΔT = 4.1 K. This research findings justify, the doping of molybdenum in the spinel lattice effectively enhances the thermoelectric properties of CuAl2O4 and provide the new ideas for the flexible, wearable fabric based thermoelectric research.

Thermoelectric properties of pristine and defective α-graphyne nanoribbons with vacancies present in different positions

In the present work, first-principle thermoelectric property investigations of pristine and defective α-graphyne nanoribbons (α-GYNRs) are conducted. Investigations have also been extended toward variation in temperature affecting the thermoelectric properties. Other objectives of the work presented are to investigate the thermoelectric properties at three temperatures, 300K, 500K, and 700K, of a single vacancy defect in a carbon atom removed from α-GYNRs. Pristine α-GYNRs is an intrinsic band gap semiconductor since defects occur naturally during synthesis, and the band gap significantly increases due to single vacancies and removal of carbon atoms at different positions. It results in a change of electrical conductivity Seebeck coefficient, and thermal conductivity. For some defective structures, with increasing temperature, the Seebeck coefficient increases compared with that of the pure structure and decreases. Also, the total thermal conductivity increases with increasing temperature. The obtained results show that the figure-of-merit value of defective α-GYNRs is much better than pristine α-GYNRs. In addition, ZT decreases in different structures by increasing temperature. Among all the considered structures, the Seebeck coefficient values and the ZT of some defective structures reach about 1.18 and 2.5 times that of the pristine structures at room temperature, respectively.

The influence of nano structuring and combined doping (Ag and Sb) on the thermoelectric properties of PbTe thin films

Nanocrystalline PbTe and Ag & Sb co-doped PbTe thin films are prepared using an integrated physical-chemical approach by evaporating chemically synthesized PbTe and Ag & Sb co-doped PbTe nanopowders on glass substrates. The X-Ray Diffractogram (XRD) reveals that all samples are NaCl-type structure and the structural parameters such as crystallite size D, dislocation density δ, strain ε, lattice constant, volume of the cell and number of crystallites are calculated and reported the results. The crystallite size of the films is around 24 nm. The absolute value of the Seebeck coefficient of nanocrystalline PbTe and Ag and Sb co-doped PbTe thin films is 1.069 mV/K and 0.569 mV/K respectively and the positive values indicate their p-type conductivity of the film. The values of Seebeck coefficient and power factor are higher than that of bulk which implies an enhancement in the thermoelectric properties with a reduction in the particle size and co doping.

Investigating novel Mo2X3S (X = Se, Te) materials: probing the influence of chalcogen substitution on electronic, optical, and thermoelectric properties

The excellent thermal performance and adjustable optoelectronic characteristics distinguish the ternary semiconductors. Using the state-of-the-art density functional theory, the optoelectronic, and thermoelectric characteristics of new Mo2X3S (X = Se, Te) ternary chalcogenides are studied. The predicted band gap values with TB-mBJ for Mo2Se3S and Mo2Te3S materials were 1.41 eV and 2.10 eV, respectively. For their possible employment in optoelectronic applications, the components of the complex dielectric function and the vital optical characteristics were calculated and studied. For an increase in the band gap and with the replacement of Se to Te, the peaks in ε 1(ω) shifted to higher energies. Mo2Se3S and Mo2Te3S both show stronger absorption in the UV and visible ranges. Based on the observed peaks in the reflection spectrum, they may used as ultraviolet-reflecting materials with good efficacy. Both Mo2Se3S and Mo2Te3S have positive Seebeck coefficient values, they exhibit p-type conduction. The Mo2Te3S material displays a maximum Seebeck coefficient at about 500 K compared to Mo2Se3S, which leads to a maximum ZT.

A new strategy to simultaneously optimize Seebeck coefficient and electrical conductivity of PEDOT:PSS polymer via L-ascorbic acid

PEDOT:PSS flexible thermoelectric materials are promising for future wearable continuous power support, but it remains challenging due to low power factor. Herein, we propose a “one-stone-two-birds” strategy using L-ascorbic acid as the reductant in synthesis of tellurium nanorods and separating agent in in-situ removing PSS chains. L-ascorbic acid reduces Te4+ to Te, supplying inorganic thermoelectric materials with high Seebeck coefficient as fillers to significantly increase the Seebeck coefficient value of PEDOT:PSS. Meanwhile, L-ascorbic acid separates PSS chains from PEDOT chains, resulting in the increase of electrical conductivity at room temperature by ∼360 % due to structure transformation from benzoid structure to the quinoid structure in PEDOT. As a result, the power factor of optimal PEDOT:PSS with Te fillers and L-ascorbic acid treatment is improved significantly by ∼100 times as compared to that of pristine PEDOT:PSS. Finally, a prototype wearable thermoelectric generator was assembled by 18 legs of Te/PEDOT:PSS composites, which demonstrates a high power density of 2.3 μW·cm−2 with good mechanical stability, flexibility and durability. The present study offers a new strategy for rational design of high-performance flexible thermoelectric materials from PEDOT:PSS.

Carbon nanotube fibers as efficient p- and n-type thermoelements within geopolymers: A route for large-scale thermal energy harvesting from building structures

This study reports for the first time, the thermoelectric (TE) performance of continuous p- and n-type carbon nanotube fiber (CNTF) filaments integrated within a sustainable, fine-grained geopolymer (GP) based concrete matrix for the complete replacement of cement with supplementary cementitious materials towards CO2 emissions reduction policy. Moreover, CNTF as CO2 negative, conductive, durable and lightweight material could multidimensionally contribute on the achievement of sustainability goals. Herein, pristine CNTF filaments were molecularly modified with p- and n-type aqueous-based dopants in order to stably tune their intrinsic semi-conducting properties via a facile and scalable dip-coating process. The achieved Seebeck coefficient values of the optimized p- and n-type CNTF were +45.2 μV/K and −38.4 μV/K, respectively. Thereafter, the p- and n-type CNTF filaments were employed as pillar-like thermoelectric elements incorporated within a GP mixture for the assembly of a structural thermoelectric generator (TEG) device. The obtained TEG-enabled GP-based concrete demonstrator comprising of 8 p-n serially interconnected junctions is capable of generating a power output of 0.3 μW at an applied through-thickness temperature gradient (ΔT) of 50 Κ. Subsequently, the experimental work was validated using coupled field of TE simulations. Self-powered infrastructures are forecasted to efficiently benefit from available ΔT on large-scale upon their operational lifetime, further promoting future net-zero energy consumption concepts.

Theoretical insight into physical characteristics of lead-free perovskites Rb2TlSbX6 (X = Cl, Br, I) for optoelectronic devices.

Novel optoelectronic and thermoelectric properties with broad compositional range, non-toxic nature and structural stability make halide-based double perovskites fascinating for flexible optoelectronic devices. In this work, the structural electronic, optical and transport properties of Rb2TlSbX6 (X = Cl, Br, I) were studied using density functional theory for optoelectronic devices. The elastic analysis demonstrates ductile nature, mechanical stability, anisotropic behaviour and feasibility for flexible optoelectronic devices. The band structure study using Tran-Blaha-modified Becke-Johnson (TB-mBJ) potential shows that all studied materials have direct bandgap. In addition, the bandgap of Rb2TlSbCl6 is more appropriate for optoelectronic devices. The small loss and maximum absorption in visible regions make these materials prime candidates for optoelectronic devices. The transport features indicate that all the studied double perovskites reflect p-type semiconducting behaviour as highlighted by positive Seebeck coefficient values. Furthermore, the high power factor values of Rb2TlSbX6 (X = Cl, Br, I) double perovskites make them suitable for thermoelectric device applications at high temperatures. Based on electronic optical and thermoelectric properties Rb2TlSbCl6 is the best candidate for flexible optoelectronic devices. In this paper, structural optimization of Rb2TlSbX6 (X = Cl, Br, I) double perovskites was conducted utilizing the Wien2k software based on first principle calculations with Perdew-Burke-Ernzerhof's generalized-gradient approximation (PBE-sol approximation). The TB-mBJ potential was employed to compute the accurate band gap of studied materials. The thermoelectric properties are evaluated with BoltzTraP code, showing a predominance of P-type charge carriers in all studied perovskites. This methodological strategy verifies the material's remarkable stability and optical properties and offers a solid framework for examining its potential in optoelectronic devices.