The ever-rising demand for energy is primarily addressed using earth’s renewable sources, out of which only a handful fraction of it is utilized and a much larger portion (greater than 70%) of it is wasted as form of heat. TE devices thus are centric for global sustainability as it utilizes the waste heat to generate electricity. Given heat’s ubiquitous nature, TE devices provide total-package solution to mitigate environmental crisis and energy needs. To put into perspective, NASA’s deep space probes, or seat climate-control system of certain cars often invariably uses thermoelectric devices to generate power at the expense of radiated heat. The governing parameter for determining its efficiency is the thermoelectric figure of merit, zT which is given by zT = (S2 σ/κ)T, where S is the Seebeck coefficient, σ is the electrical conductivity, and κ is the thermal conductivity.
We actively pursue research in design and development of high performance TE materials based mainly on bulk/nano metal chalcogenides via parallel approaches of enhancing S2σ and suppressing κ. We aim to enhance S2σ by carrier engineering via extrinsic chemical doping, and modification of electronic structure via formation of resonant levels, band convergence etc. On the other hand, κ can be suppressed extrinsically through formation of point defects, endotaxial nanostructures, intergrowth compounds etc.
We also explore materials which, by the virtue of their unique structural topology, exhibit intrinsic glass-like thermal conductivity and crystal like electrical conductivity. We strive to understand unique lattice dynamics and the ensuing ultralow thermal conductivity in systems having rattling sublattices. We also investigate at the bonding environment and atom dynamics within the crystal structure at an atomic level where the presence of ns2 lone pair of electrons causes strong lattice anharmonicity. We aspire to comprehend the underlying chemistry involved in materials with colossal thermopower change, n-p type structural phase transitions and other interesting phenomena.
Our group pursues thermoelectric studies on chalcogenides of lead, bismuth, tin germanium, noble metal-based chalcogenides, pnictides etc.
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