Faculty Publications
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Item Electronic structure modulation of Pb0.6Sn0.4Te via zinc doping and its effect on the thermoelectric properties(Elsevier Ltd, 2021) Shenoy, U.S.; Bhat, D.K.Striking a balance between the high performance and detrimental environmental toxicity of PbTe materials in thermoelectrics (TE) has become a necessity in the current situation. In this context, improving the performance of materials with lower lead content to the level of PbTe is crucial. Herein, we engineer the electronic structure of Pb0.6Sn0.4Te, a well-known TCI but a poor TE material by doping Zn. The first principles calculation reveal that Zn doping introduces multiple electronic valleys while simultaneously opening the band gap of Pb0.6Sn0.4Te. Higher power factor with lower thermal conductivity is predicted by the transport property calculations in the doped material. The resonance level introduced along with features of hyper-convergence of the valence bands leads to improved Seebeck co-efficient throughout the studied temperature range. An experimental figure of merit, ZT of ~1.57 at 840 K promises us a TE material applicable for a broad temperature range for future energy applications. © 2021 Elsevier B.V.Item Selective co-doping improves the thermoelectric performance of SnTe: An outcome of electronic structure engineering(Elsevier Ltd, 2022) Shenoy, U.S.; Bhat, D.K.Thermoelectric materials which exhibit high performance throughout a range of temperature is required for successful scavenging of waste heat to generate electricity. Herein, we tailor the electronic structure of SnTe by co-doping Zn with three elements namely Ag, Ca and Mg. We observe that the dopants play complementary roles and improve the thermoelectric performance throughout the studied temperature range. Zn introduces resonance level and causes hyper-convergence to increase the Seebeck at low temperatures while M (M = Ag, Ca, Mg) enlarges the band gap preventing bipolar transport and also helps in the band convergence improving the performance at higher temperatures. The enhanced thermoelectric properties predicted by theoretical calculations is supported by experimental results. For the same concentration of doping, AgZn co-doped SnTe exhibits higher performance compared to the other two with an impressive ZT of ~1.54 at 840 K and average ZT of ~0.97 between 500 K and 840 K. © 2021 Elsevier B.V.Item A case of perfect convergence of light and heavy hole valence bands in SnTe: the role of Ge and Zn co-dopants(Royal Society of Chemistry, 2022) Shenoy, U.S.; D, G.K.; Bhat, D.K.A dual step approach of decreasing the thermal conductivity and improving the power factor by using two different dopants has shown great promise in the development of high performance thermoelectrics. In this work, we dope Ge, which is well known to decrease the thermal conductivity of SnTe. Later, to this, we co-dope Zn to simultaneously improve the power factor. Zn, in the presence of Ge, introduces resonance levels, thus distorting the density of states near the Fermi level, improving the room temperature performance. In addition, it is also able to increase the band gap, thus preventing bipolar diffusion at high temperatures. The unique feature exhibited is the perfect convergence of light and heavy hole valence sub-bands achieved for the first time in SnTe promising a high performance throughout the temperature range. The transport property calculations reveal that in addition to p-type, it can also act as an outstanding n-type material by tuning its chemical potential, making it worth studying experimentally. © 2022 RSC.Item Tailoring the Thermoelectric Performance of the Layered Topological Insulator SnSb2Te4 through Bi Positional Doping at the Sn and Sb Cation Sites(American Chemical Society, 2023) Kihoi, S.K.; Shenoy, U.S.; Kahiu, J.N.; Kim, H.; Bhat, D.K.; Lee, H.S.Ongoing research and development focus on emerging thermoelectric materials with enhanced performance, continually making the possibility of waste heat recovery a reality. In this work, we engineer the thermoelectric properties of the layered SnSb2Te4 topological insulators. To date, there is little research reporting on these materials as potential state-of-the-art thermoelectric materials. Thus, there is a need to formulate effective strategies to realize this potential. Since these materials are known to have intrinsically low lattice thermal conductivity, we shift our attention to improving the electrical transport properties. For the first time, positional Bi doping at both the Sn and Sb cation sites is adopted. The aliovalent and isovalent nature of Bi at these sites, respectively, is shown to cause significant improvements in the performance of these layered materials. The electronic band structure of the pure and doped samples, where we considered various occupancies, is studied whereby we reveal the occurrence of band convergence and resonant levels resulting in a high power factor of ∼10.8 μW cm-1 K-2 at 623 K. Overall, a high ZT of ∼0.46 at a relatively lower temperature of 673 K is recorded. The potential of these materials for thermoelectric applications is shown, especially in the case of Bi doping at the Sn cation site. Continued efforts to enhance the thermoelectric performance of these topological insulators are needed for them to gain a substantial competitive edge in comparison to other state-of-the-art thermoelectric materials. © 2023 American Chemical Society.Item Enhanced photoresponse and efficient charge transfer in porous graphene-BaTiO3 nanocomposite for high performance photocatalysis(Elsevier Ltd, 2023) Bhat, D.K.; Bantawal, H.; Uma, U.; Shenoy, U.S.Porous graphene-BaTiO3 (PGBT) nanocomposite was synthesized by a simple one pot solvothermal method and its photocatalytic activity was evaluated by studying its efficiency in degrading methylene blue (MB) dye under visible light. The combination of experimental and theoretical analysis revealed enhanced photocatalytic activity of the PGBT composite, which could be attributed to (i) the interaction of BaTiO3 nanoparticles with PG sheets via Ba–C bond, (ii) reduced band gap due to the introduction of hybridized states leading to increased absorption in visible range and (iii) large surface area which provides more active sites for the efficient adsorption of MB dye. The formation of Ba–C bond proved to be highly advantageous for the efficient transport of photogenerated charge carriers, thereby suppressing the recombination of charge carriers. The synthesized nanocomposite showed three times higher photodegradation efficiency compared to BaTiO3. In addition to this, the composite also showed an excellent cyclic stability indicating its suitability as an effective photocatalyst for the environmental remediation. © 2023 Elsevier B.V.Item Towards achieving an ideal convergence of light and heavy electron conduction bands in SnTe: Insights into copper doping(Elsevier B.V., 2024) Shenoy, U.S.; Bhat, D.K.In recent years, tin telluride has garnered significant attention in the field of thermoelectrics, offering a promising avenue for sustainable ecofriendly conversion of waste heat into electricity. The unique electronic structure of this material makes it a compelling candidate for exploring innovative strategies to enhance its transport properties by employing substitutional doping. Among myriad elements doped, copper has been considered an intriguing candidate due to its ability to lower the thermal conductivity. However, its impact on the electronic structure has not been thoroughly explored till date. Herein, we investigate a nuanced aspect of copper doping, specifically focusing on its impact on tuning the electronic structure of SnTe. Significantly, our findings reveal a novel dimension to copper doping, showcasing its potential to enhance n-type performance in SnTe through the near-perfect convergence of its conduction bands - a feature not observed when doped in GeTe. We also shed the light on improvement of the p-type performance by means of valence band convergence and increased band gap. Furthermore, we reveal that copper doping allows the contribution of low-lying bands in SnTe to participate in transport, ensuring a higher Seebeck coefficient across the entire temperature range. Overall, this work provides a panoramic view of role of copper in improving the Seebeck co-efficient of SnTe making it a potential lead-free material for several thermoelectric applications. © 2024 Elsevier B.V.Item Tuning the electronic structure of rhombohedral and cubic GeTe for thermoelectric application: Influence of molybdenum doping(Elsevier Ltd, 2024) Shenoy, U.S.; Bhat, D.K.Substitutional doping to engineer the electronic structure of materials has received high prominence in developing high performance thermoelectric materials. Herein, we study the effect of molybdenum doping on the electronic structure of GeTe and provide insights into the observed enhancement of thermoelectric performance. We discover that Mo doping has a huge impact on the band structure of both rhombohedral and cubic phase of GeTe. In addition to increasing the band gap, Mo doping causes huge increase in the density of states near the Fermi level. We also notice convergence of valence sub-bands and hyperconvergence of conduction sub-bands besides introduction of multiple carrier valleys promoting transport in both p and n-type materials. These features undoubtedly make Mo doping a beneficial approach in the development of lead free GeTe thermoelectrics. © 2024 Elsevier LtdItem Formulation and optimization of Ni-MOF/CuSe nanocomposite ink for high-performance flexible microsupercapacitor(Elsevier Ltd, 2024) Saquib, M.; Muthu, M.; Nayak, R.; Prakash, A.; Sudhakar, Y.N.; SenthilKumar, S.; Bhat, D.K.The growth of flexible and wearable electronics drives progress in printed, flexible micro-supercapacitors for energy storage. This study fabricates flexible and foldable micro-supercapacitors using a nanocomposite of Ni-based Metal-Organic Framework (Ni-MOF) and copper selenide (CuSe). The conductive ink, blending Ni-MOF and CuSe, ensures thorough mixing for screen-printing. The resulting devices exhibit impressive electrochemical performance, with the NC-5 FAS device showing high areal capacitance, promising energy density and (3.65 mWhcm?2 and power density (73.8 mWcm?2). Integration into a 3D enclosure configuration enhances performance, with improved capacitance, energy density (47.08 mWhcm?2) and power density and outstanding power density (985.8 mWcm?2), maintaining capacitance retention of the 93.9 % and with highly robust mechanical durability during flexibility tests. This study highlights tailored nanocomposite's potential to revolutionize flexible and foldable energy storage, advancing high-performance, portable electronics. © 2024Item Enhanced flexibility and performance of interdigitated microsupercapacitors through in-situ rGO growth in NiCuSe nanocomposite conductive ink(Elsevier Ltd, 2025) Saquib, M.; Nayak, R.; Muthu, M.; Bhat, D.K.; Rout, C.S.Microsupercapacitors (MSCs) are promising alternative power sources capable of meeting the growing demand for wearable and on-chip electronics due to their compact size, lightweight nature, exceptional charge-discharge rates, high power densities, and superior flexibility. However, a major challenge in current MSCs development lies in their limited energy density, high-cost, and time-intensive fabrication processes. This study focuses on fabricating flexible interdigitated printed MSCs using in-situ growth of reduced graphene oxide within nickel-copper selenide nanocomposite inks via screen printing. The eco-friendly ink formulation incorporates ethyl cellulose, diacetone alcohol, and a non-ionic surfactant to optimize printability, viscosity, and post-drying efficacy. The MSCs achieved a high areal capacitance of 756.3 mFcm?2 at 5 mVs?1, with energy densities of 84.4 µWcm?2 (symmetric) and 151.2 µWhcm?2 (asymmetric), and corresponding power densities of 406 mW cm?² and 1210 mW cm?². The printed devices retained 94.2 % of their capacitance on PET (Polyethylene terephthalate) substrates and exhibited excellent mechanical stability under bending, making them ideal for wearable electronics and flexible IoT applications. These results highlight the potential of the fabricated screen-printed MSCs, leveraging the optimized electrode material, as a high-performance and eco-friendly energy storage technology for next-generation flexible electronics. © 2025 The Authors