Thermoelectric Devices Research Articles

High thermoelectric and opto-electronic properties of Ba3NX3 (X=F, Cl) perovskite: Insights from DFT computation

Researchers are working for discovering smart and efficient materials to cope with energy crises. Amongst them, Perovskite are explored extensively by researchers owing to their role in energy harvesting. In this study, structural, elastic, electronic, optical and thermoelectric properties of halide perovskites Ba3NX3 (X = F, Cl) have been explored by using density functional theory techniques. The permissible values of tolerance factor and formation energy ensure the structural and thermodynamic stability of these compounds. Band structure calculations revealed that both materials have semiconducting nature, with the band gap of ∼2.1 eV and 1.9 eV for Ba3NF3 and Ba3NCl3 respectively. The elastic constants suggest both compounds are mechanically stable and exhibit ductile nature. Optical response is studied in the energy range of 0–40 eV of photons. The absorption peaks are observed from 2 eV to 25 eV. Furthermore, it is observed that the relaxation time for Ba3NF3 is longer than Ba3NCl3. Thermoelectric properties such as Seebeck coefficient, electrical conductivity electronic thermal conductivity and figure of merit (ZT) are obtained using BoltzTrap2 code. It is observed that for both materials Seebeck coefficient has almost same maximum value of 1.54 × 10−3 V/K at 300K. The ZT values are found to be 1.23 for Ba3NF3 while 0.9 for Ba3NCl3 at 700K. This work demonstrates that these halides perovskites have a lot of potentiality to prove themselves as best candidates for solar cells and for thermoelectric devices.

High-Performance SnTe Thermoelectric Materials Enabled by the Synergy of Band Convergence and Phonon Scattering.

SnTe, an environmentally friendly thermoelectric material, has garnered widespread scholarly interest owing to its lead-free nature; however, its intrinsic thermoelectric performance is constrained by a relatively low Seebeck coefficient and an extremely high lattice thermal conductivity. In this investigation, we employ the alloying of Ge and AgSbTe2 to enhance the zT value of SnTe. The study found that Ge, Ag, and Sb can effectively enhance the Seebeck coefficient and power factor of SnTe by utilizing band convergence. At the same time, a multitude of point defects induce phonon scattering, consequently decreasing the lattice thermal conductivity of SnTe. Collectively, these synergistic effects result in Sn0.75Ge0.25Te-15% AgSbTe2 achieving its highest zT value of 1.28 at 823 K, with an average zT value of 0.77 between 400 and 823 K. Such high zT values of the SnTe-based thermoelectric material provide the potential for applications in high-performance solid-state thermoelectric devices.

Topology optimization design for voltage enhancement in variable structure double-layer flexible thermoelectric devices

Flexible thermoelectric devices possess the capability to generate electricity by harnessing temperature differences, rendering them highly promising for applications in wearable devices and powering the Internet of Things. This paper introduces a topology optimization design approach for double-layer thin-film flexible thermoelectric devices with the aim of enhancing the device's output voltage and improving the efficiency of green energy utilization. The design process took into consideration the coupled effects of mechanical, electrical, and thermal aspects. It not only optimized the force transmission paths of the variable structure device but also accounted for heat dissipation and circuit topology configuration. The study employed a field function model to concurrently optimize the structure of both the substrate and thermoelectric materials in an integrated design, with the primary objective being the maximization of output voltage. The efficacy of this methodology was confirmed through a series of numerical simulations and experiments conducted under various load and operational conditions. The optimized flexible thermoelectric devices exhibited an output voltage increase of more than threefold when compared to flat devices.

Thermal flow and thermoelectricity characteristics in a sandwich flat plate thermoelectric power generation device under diesel engine exhaust conditions

Thermoelectric power generation (TEG) technology can be used to recover exhaust waste heat, but its effective application is restricted by bulky size and low thermoelectric conversion efficiency. The compactness evaluation of thermoelectric devices characterized by the power density is lacking. In this paper, a three-dimensional thermal flow and thermoelectricity multi-physics field model of a sandwich flat plate TEG device with multi-layer thermoelectric modules (TEMs) was established. An engine thermoelectric recovery bench test was carried out to verify the model and present the thermal parameters and output performance. The thermal, flow and electrical field distributions of the TEG device, as well as voltage, power and conversion efficiency with engine loads, and power density, were presented. The results show that the hot side temperatures, voltages and powers for each thermoelectric module (TEM) are greatly affected by the position occupied by the TEMs and engine loads. At full load and the coolant flow of 8.5 L/min, the device achieves the peak values of the power of 80.9 W and thermoelectric efficiency of 2.1 %, respectively. The device shows good compactness with the power density of 19.8 kW/m3, attributed to the reasonable arrangement of the collectors, coolers, and TEMs. This work can provide some insights of the relationship between the structural form and size, thermal parameters, electrical parameters and conversion efficiency of the sandwich type TEG device.

Exploring the Thermal and Ionic Transport of Cu+ Conducting Argyrodite Cu7PSe6

AbstractUnderstanding the origin of low thermal conductivities in ionic conductors is essential for improving their thermoelectric efficiency, although accompanying high ionic conduction may present challenges for maintaining thermoelectric device integrity. This study investigates the thermal and ionic transport in Cu7PSe6, aiming to elucidate their fundamental origins and correlation with the structural and dynamic properties. Through a comprehensive approach including various characterization techniques and computational analyses, it is demonstrated that the low thermal conductivity in Cu7PSe6 arises from structural complexity, variations in bond strengths, and high lattice anharmonicity, leading to pronounced diffuson transport of heat and fast ionic conduction. It is found that upon increasing the temperature, the ionic conductivity increases significantly in Cu7PSe6, whereas the thermal conductivity remains nearly constant, revealing no direct correlation between ionic and thermal transport. This absence of direct influence suggests innovative design strategies in thermoelectric applications to enhance stability by diminishing ionic conduction, while maintaining low thermal conductivity, thereby linking the domains of solid‐state ionics and thermoelectrics. Thus, this study attempts to clarify the fundamental principles governing thermal and ionic transport in Cu+‐superionic conductors, similar to recent findings in Ag+ argyrodites.

Exceptional thermoelectric and mechanical performance in (Bi, Sb)2Te3 matrix facilitated by AgInSe2 alloying

The emerging fields of the Internet of Things, intelligent robotics, and smart biomedical devices have sparked an increasing demand for high-performance thermoelectric (TE) devices due to their efficient conversion of thermal energy into electrical power, and vice versa. The environmentally friendly (Bi, Sb)2Te3 (BST) system, which displays superior performance near room temperature, offers a promising solution for optimizing thermoelectrics to meet the needs of commercial applications. Here, we utilized AgInSe2 alloying to enhance the TE and mechanical properties of BST, aiming to optimize electron and phonon transport and elucidate the underlying mechanisms. The synergistic optimization resulted in a peak zT of ∼ 1.3 at 353 K and an average zTave of ∼ 1.11 from 303 K to 503 K in BST-0.1 %AgInSe2, as well as a high Vickers hardness of ∼ 105 Hv. Through rational optimization of the TE device, we achieved a maximum conversion efficiency of ∼ 6 % at a temperature difference of 210 K. Leveraging the robust TE output of the device, we further evaluated its potential as a self-powered information interaction wristband device based on ASCII codes. We envisage this versatile TE device being extensively applied in power generation and human–machine interaction, with promising potential in wearable electronics, telecommunications, and healthcare monitoring.

(Invited) 3D Printing for Tissue Scaffolds with Tunable Mechanical Durability and Sensing Capabilities

Pelvic organ prolapse (POP) is a prevalent condition among senior women, characterized by the descent or herniation of pelvic organs into the vaginal canal. It is a widespread issue, affecting a significant portion of the elderly female population, and yet, effective medical solutions for this condition remain elusive. This can be attributed to the complex nature of POP, where multiple factors, including tissue weakening and structural changes, contribute to its development. Despite the significant impact on women's quality of life, the absence of comprehensive treatment options underscores the urgency for innovative approaches to address this pressing health concern. In this context, 3D printing emerges as a valuable rapid prototyping tool, offering unique capabilities for designing and fabricating smart sensors and actuators. Its precision and versatility enable the creation of intricate devices that can be customized to specific medical applications. Moreover, 3D printing allows for the integration of sensors directly into biomedical devices, facilitating seamless monitoring and feedback mechanisms. Leveraging this technology, the research endeavors to harness the potential of 3D printing to develop advanced thermoelectric devices that can be seamlessly embedded within POP tissue scaffolds. These innovative devices will serve a dual purpose—detecting the health status of the tissue scaffolds and assessing their mechanical durability. In the realm of embedded medical devices, self-powered sensors hold particular significance due to their wireless powering capabilities and in-situ monitoring capabilities of human health. These sensors can operate without the need for external power sources or frequent battery replacements, making them ideal for long-term implantation within the human body. By tapping into the body's own energy sources or ambient environmental factors, self-powered sensors ensure continuous data collection and transmission, enhancing the efficiency and reliability of healthcare monitoring systems. Consequently, this talk aims to demonstrate the feasibility of 3D-printed thermoelectric devices as self-powered sensors, integrated into POP tissue scaffolds. These innovative devices will play a pivotal role in monitoring the tissue scaffold's condition, ensuring its mechanical integrity, and ultimately contributing to improved healthcare outcomes for women affected by POP.

(Invited) Epitaxial Growth of Quasi-Low Dimensional Materials for Novel Thermoelectric Films

Thermoelectric conversion devices or modules with high performance have been expected for the electrical power generation from wasted heat. Then, thermoelectric materials with high dimensionless figure of merit zT at temperature T , described as S 2 σT/κ have been intensively sought, where S is Seebeck coefficient, σ is electrical conductivity, and κ is thermal conductivity. Therein, intercorrelation among three thermoelectric properties has been a big barrier against high zT. In conventional approach, the heavy elements such as rare metals are used because they inherently bring small κ in the materials. Now, ecofriendly ubiquitous element materials without toxic, rare, or high cost elements, showing high zT, are expected in the application view.Introduction of nanostructures into materials is one of the promising ways to increase zT because of phonon scattering [1], quantum confinement effect in low dimensional materials and by energy filtering [2], and so on. Therein, structure design determines the properties, and then, this method can be expected to bring high zT in the ecofriendly and low-cost ubiquitous element materials. Furthermore, it is recently found that low dimensional materials and quasi-low dimensional materials such as layered materials with 2D structures in the unit cell show high zT values. Therefore, low and quasi-low dimensional materials for extraordinarily high zT values have been expected to be developed.We have been developing a lot of kinds of well-controlled nanostructure films by SiO2 film technique. One of the examples: Si-based films including ultrasmall semiconductor nanodots with controlled interfaces, strains, crystal orientations, and compositions [3]. Furthermore, we have developed the epitaxial growth method of quasi-low dimensional material films composed of ecofriendly group IV elements on Si substrates: FeGeγ including 1D Ge helical structure and Ca-intercalated multi-layered silicene films. Here, we will introduce the epitaxial growth results of quasi-low dimensional material films. Epitaxial growth of FeGeγ films on Si were achieved by using Ge epitaxial nanodots as seed crystals[4]. In the case of Ca-intercalated multi-layered silicene, silicene bucked structure was found to be deformed. The deformation enhanced Seebeck coefficient. As a result, this sub-angstrom atomic displacement brought power factor enhancement while keeping high electrical conductivity [5]. In this talk, we will present the epitaxial growth process of quasi-low-dimensional material films on Si substrates for thermoelectric film devices composed of ecofriendly and low-cost thermoelectric materials .[1] Y. Nakamura, et al., Nano Energy 12, 845 (2015).[2] T. Ishibe, et al., ACS Appl. Mater. Inter. 10, 37709 (2018).[3] Y. Nakamura, et al., Sci. Technol. Adv. Mater. 19, 31 (2018).[4] T. Terada, Acta Materialia 236, 118130 (2022).[4] T. Terada, et al., Adv. Mater. Inter. 9, 2101752 (2022).

Evaluation of Thermal Transport Characteristics of Three-Dimensional Self-Ordered Multilayered Silicon-Germanium Nanodots

1. Background and purpose Silicon-germanium (SiGe) alloys have much lower thermal conductivity than Si and Ge single crystals and are expected to be candidates for next-generation thermoelectric device materials of internet of things society. It is important to achieve both high carrier mobility and low thermal conductivity on the basis of the dimensionless figure of merit [1]. There are several studies on the thermoelectric properties of SiGe with low-dimensional structures such as superlattice and nanodots [2,3] to dramatically decrease thermal conductivity. However, the relationship between the nanoscale thermal properties and the phonon scattering mechanism of self-ordered multilayer SiGe nanodots with high uniformity grown by Stranski-Krastanov [4] mode is unclear. In this study, we demonstrated the thermal transport characteristics of the self-ordered multilayer SiGe nanodots. 2. Experiments Si/SiGe superlattice and nanodots samples were fabricated by reduced pressure chemical vapor deposition. We set to 20 cycles of Si0.65Ge0.35 / Si superlattice, the staggered Si0.65Ge0.35 nanodots (alternately stacked) and the dot-on-dot Si0.65Ge0.35 nanodots (vertically stacked) by changing growth temperature and precursors for Si spacer growth [4], as shown in Fig. 1. Thermal properties were evaluated by the Time Domain Thermoreflectance (TDTR) method. The strain states and Ge fraction were evaluated by Raman spectroscopy. The focal length and wavenumber resolution of the Raman spectrometer were 2,000 mm and 0.1 cm-1, respectively. The excitation light source was a green laser (wavelength: 532 nm). We obtained the Raman spectra of Si-Si, Si-Ge, and Ge-Ge vibrational modes derived from the SiGe regions. 3. Results and discussion Figure 2 shows the thermal conductivity for the SiGe region of the superlattice and nanodots (dot-on-dot and staggered structures) obtained by TDTR method. We found that the SiGe nanodots with the dot-on-dot structure have the highest thermal conductivity, while the SiGe nanodots with the staggered structure and SiGe superlattice have almost the same thermal conductivity. We consider that the heat flow easily penetrates from the top (surface) to the bottom (Si substrate interface) in the dot-on-dot structures. On the other hand, it is possible that the staggered SiGe nanodots can play a sufficient role as a phonon scatterer compared to the dot-on-dot structures since the superlattice structure and the staggered SiGe nanodots have almost the same thermal properties. In conclusion, we demonstrated the possibility of controlling phonon scattering by changing the arrangement of the self-ordered multilayer SiGe nanodots. Acknowledgement This work was supported by JSPS KAKENHI Grant Number 21K14201, Japan.

A novel characteristic curve for thermoelectric cooler application in realistic thermal circumstances: Theory and experiment

On the materials level, the performance of thermoelectric (TE) devices can be defined by the thermoelectric figure of merit (zT). This, however, does not provide a complete picture due to the complex interplay between electronic and thermal transport properties and the uncertain thermal impedance matching between external and internal thermal resistances in different realistic thermal circumstances. Appropriate design of individual material properties and geometry parameters considering the realistic thermal circumstance can greatly enhance the device-level performance of TE devices. In this work, we develop a framework to clarify such interactions in thermoelectric coolers (TEC) with a newly proposed q-h characteristic curve, which can be used to identify how a TEC design is of effectiveness for a specific realistic thermal circumstance. The effects of zT, the individual TE material properties (i.e., thermal conductivity k, electrical conductivity σ and Seebeck coefficient S) as well as the geometry parameters (i.e., pillar height and filling factor) on the q-h characteristic curve are theoretically and experimentally investigated, respectively. TEC modules with higher zT, short pillars and high filling factor show stronger capability to handle high heat flux load, especially for the cases with high heat dissipation coefficient at hot side. The thermal property (k) and electrical properties (σ and S) are responsible for the low heat flux load (e.g., wearable TEC) and high heat flux load (e.g., on-chip TEC cooling), respectively. For wearable TEC, increasing the internal thermal resistance can prevent the back flow heat, which can be achieved with tall pillars, low filling factor and optimizing zT towards lowering thermal conductivity k. For on-chip TEC cooling, reducing the Joule heating and increasing the thermoelectric effect become dominant factors in lowering the code-side temperature of TEC modules. This can be achieved with short pillars, high filling factor and optimizing zT towards increasing the power factor S2σ. This work provides significant insights into the complex interplay between material-level properties, device-level parameters and the external thermal circumstance in determining the performance of TEC devices. The results enable researchers to design optimal TEC devices for realistic applications with different boundary conditions.

Wearable, Knitted 3D Spacer Thermoelectric Generator with Detachable p-n Junctions for Body Heat Energy Harvesting.

Textile-based thermoelectric (TE) devices are being investigated to power smart textiles autonomously. While previous research has focused on a solid system where the required junctions are fabricated into the device, there has been limited attention given to replacing these TE systems reliably. This work looks at a newer approach to the construction and demonstration of a wearable thermoelectric structure that employs three-dimensional knitted spacers to increase the temperature difference where the TE junctions are detachable and disposable. This system features positive and negative junctions which can be removed while maintaining its excellent voltage generation in low ΔT and good Seebeck coefficients. A mathematical model simulates the potential energy outputs and maximum power points generated, which can be used to increase the device's performance for future wearable sensing applications.

Series/Parallel Switching for Increasing Power Extraction from Thermoelectric Power Generators.

We propose a method for increasing power extraction from a thermoelectric generator (TEG) by switching between series/parallel circuit configurations of thermoelectric elements, which can adjust the internal impedance of the TEG. The power characteristics of the TEG can be adjusted to the load characteristics of the connected device and the relevant ambient temperature. In this paper, we analyzed the change in the TEG characteristics with the series/parallel switching function. We evaluated the power supply to the connected devices at different ambient temperatures and different series/parallel configurations and confirmed that the extracted power could be increased. By theoretically analyzing the circuit configuration of the thermoelectric devices, the switching required to improve the power extraction, and the temperature difference at which switching occurred, we devised a design method for a TEG with circuit switching in order to increase power extraction with any device. We demonstrated the configuration of switching by using a system in which a TEG supplied power to an external wireless transmitter circuit. In this system, the optimal configuration differed at temperature differences of 3.0 K and 4.0 K. At a temperature difference of 3.0 K, the 2-series/1-parallel configuration provided 10% more power to the external circuit than the 1-series/2-parallel configuration. On the other hand, at the temperature difference of 4.0 K, the 1-series/2-parallel configuration provided 23% more power than the 2-series/1-parallel configuration.

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.

Poly(benzodifurandione) Coated Silk Yarn for Thermoelectric Textiles.

Thermoelectric textile devices represent an intriguing avenue for powering wearable electronics. The lack of air-stable n-type polymers has, until now, prevented the development of n-type multifilament yarns, which are needed for textile manufacturing. Here, the thermomechanical properties of the recently reported n-type polymer poly(benzodifurandione) (PBFDO) are explored and its suitability as a yarn coating material is assessed. The outstanding robustness of the polymer facilitates the coating of silk yarn that, as a result, displays an effective bulk conductivity of 13 S cm-1, with a projected half-life of 3.2 ± 0.7 years at ambient conditions. Moreover, the n-type PBFDO coated silk yarn with a Young's modulus of E = 0.6GPa and a strain at break of εbreak = 14% can be machine washed, with only a threefold decrease in conductivity after seven washing cycles. PBFDO and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) coated silk yarns are used to fabricate two out-of-plane thermoelectric textile devices: a thermoelectric button and a larger thermopile with 16 legs. Excellent air stability is paired with an open-circuit voltage of 17mV and a maximum output power of 0.67 µW for a temperature difference of 70 K. Evidently, PBFDO coated multifilament silk yarn is a promising component for the realization of air stable thermoelectric textile devices.

Grain Manipulation by Annealing Treatment Realizes High-Performance N-Type Bi2Te2.4Se0.6 Thermoelectric Material and Device.

Bi2Te3-based materials play a crucial role in solid cooling and power generation, but the rapidly deteriorated ZT with rising temperatures above 450 K severely limits further applications. Here, this paper reports a novel preparation method of annealing treatment for molten ingot, which can enhance the thermoelectric performance of n-type Bi2Te2.4Se0.6 in a wide temperature range. Instead of conventional halides, copper is adopted to regulate the carrier concentration and grain size to optimal levels. During the process of annealing at 573 K for 4h, the number of twins significantly increases and the grains of Cu-doped samples become larger and more oriented. These optimizations lead to higher carrier mobility with similar carrier concentration compared with the sample without heat treatment. The synergistic effects of Cu doping and annealing treatment realize a high average ZT of 0.89 within 300-600 K in n-type Cu0.02Bi2Te2.4Se0.6. Combined with p-type (Bi,Sb)2Te3, the fabricated thermoelectric device exhibits a high conversion efficiency of 6.9% at a temperature difference of 300 K. This study suggests that annealing treatment is a simple and effective scheme to promote the applications of n-type Bi2(Te,Se)3 in a wide temperature range.

Thermoelectric device for the treatment of panaritium by local hypothermia

Thermoelectric device for the treatment of panaritium by local hypothermia

Cellulose binary coatings with spherical envelope structure via structure rearrangement in ball milling for integrated radiative cooling-electricity generation

Passive daytime radiative cooling is a zero-energy consumption cooling technology, which can dissipate heat to outer space via infrared radiation. Recently, coupling radiative cooling technology and thermoelectric devices to generate electricity has attracted much attention. However, existing radiative cooling integrated thermoelectric devices still suffer from low-temperature gradient and output voltage. Here, based on the Mie scattering and internal reflection enhancing principle, an impact-inducing geometry reconstruction approach was proposed to fabricate hierarchical nanostructured cellulosic coatings with good daytime cooling performance to achieve stable electricity generation function, which can be realized by using a scalable and facile wet ball milling technology. Guided by the theoretical simulations of the finite difference time domain method (FDTD), the cellulose and TiO2 nanoparticles can assemble into spherical envelope structured coatings drying by the shear, impact, and friction interaction in the ball milling process, dramatically enhancing the Mie scattering and internal reflection of coatings. The cellulosic coatings exhibit sunlight reflectivity of 0.962 and infrared emissivity of 0.94, resulting in a daytime radiative cooling efficiency of 5.9 °C under direct sunlight. Energy Plus stimulation demonstrated 35 % cooling energy and 468.9 kWh of cooling energy can be saved annually in China. Meanwhile, this cellulosic coating-based thermoelectric device can deliver a high voltage output of 150 mV under 1 Sun due to the strong bonding and high-temperature gradient formation (30 °C), which is higher than previous reports. This study will facilitate the development of sustainable power generation device for the goal of green future.

DFT study of optoelectronic and thermoelectric properties of pure and doped double perovskite Cs2SnI6 for solar cell applications

The global need of energy is raising day by day. To meet this demand double perovskites (DPs) can play a vital role for energy conversion devices. In this letter, we formulated and examined lead-free defect perovskites using a combination of tellurium and tin, denoted as Cs2Sn1-xTexI6 (0, 0.25), utilizing density functional theory which include structural, optical and thermal behavior. Both the optimized volume and lattice parameter exhibit a linear increase with the Te content in Cs2Sn1-xTexI6 (CsSnTeI). The negative value of formation energy for both pure and doped materials along with their Poisson and Pugh ratio confirm the stability of these materials. The band structure analysis reveals its semiconducting behavior, with the band gap expanding proportionally to the increased Te concentration with band gap value of pure (1.20 eV) and doped 91.43 eV) double perovskites. Optical characteristics, including the dielectric function and absorption coefficient, were also analyzed. To expose their potential use of Cs2Sn1-xTexI6 (0, 0.25) in thermoelectric devices, temperature dependent thermoelectric features are investigated reveal that suitability of these materials for energy conversion purposes.

Evaluation of the phonon, optoelectronic, photovoltaic, thermoelectric, photocatalytic and thermodynamic properties of the inorganic perovskite CsPbI2Br using Ab initio calculations

Inorganic CsPbI2Br perovskites, derived from cesium, hold potential for use in solar and optoelectronic devices. This study utilized density functional theory calculations to investigate the structural, phonon, electronic, optical, photovoltaic, thermoelectric, thermodynamic, and photocatalytic properties of CsPbI2Br. The phase stability of our compound is thoroughly researched, and it is confirmed that all are thermodynamically and dynamically stable. Formation energy is employed to confirm thermodynamic stability while phonon dispersion is used to confirm dynamical stability. We have computed the electronic properties of CsPbI2Br, such as PDOS, TDOS, and its band structure. The results indicate that the material is a p-type semiconductor which has a direct gap value of 1.50 eV and 1.92 eV using GGA-PBE and TB-mBJ respectively. Higher absorption coefficient, optical conductivity, reflectivity and other optical properties of the CsPbI2Br compound indicate better absorption in the visible spectrum. This distinguishes this substance as an exceptional candidate for optoelectronic devices. Improved utilization of CsPbI2Br in thermoelectric devices is evident from the power factor PF, Seebeck coefficient, figure of merit, and other thermoelectric properties. CsPbI2Br is advantageous in the solar industry due to its external quantum efficiency, open-circuit voltage of 1.92 V, and short-circuit current of 19.67 mA.cm−2. Additionally, the study examined the compound’s thermodynamic properties and examined how the temperature affected its entropy, free energy, enthalpy and heat capacity. Furthermore, it meets the thermodynamic necessary conditions to initiate the water-splitting reaction; the CsPbI2Br compound demonstrates strong photocatalytic performance. This implies that CsPbI2Br may open up new avenues for thermoelectric and optoelectronic experimentation.

Insight view of thermal, mechanical and structural behavior of novel double perovskites Ba2XSbO6 (X = Sc, Y): A DFT based study

The study of double perovskite structures Ba2XSbO6 (X = Sc, Y) is carried out using the first principles algorithms within the framework of Density Functional Theory (DFT). The results showed that these compounds possess a cubic perovskite structure with the lattice space group Fm-3m generally represented by the group No. 225. The band structure of these compounds confirms their insulating nature. The calculated values of elastic parameters determined the brittle nature of Ba2ScSbO6 and Ba2YSbO6 compounds. Positive frequencies of the phonon dispersion curve indicates that these double perovskites are dynamically stable, with one acoustic and ten optical phonon modes having the combination of Raman active, Infrared active and optically inactive modes. The transport properties of these materials including electrical and thermal conductivity, as well as their thermoelectric power have been investigated. Additionally, the figure of merit was calculated to assess the suitability of double perovskites for thermoelectric devices and advanced technological applications.