Computational Physics, Density functional theory, Phonon dynamics, Ab-initio Molecular dynamics, Chemical bonding analysis
Thermoelectricity, Optoelectronics, Nanoelectronics
Boltmann transport theory, Carrier Transport properties, Electrical and thermal conductivity
Hot carrier dynamics for optoelectronics applications in organic/inorganic/hybrid materials.
Composition and surface topology dependent carrier transport behaviour in layered and bulk material.
Designing of ultrahigh dielectric material for energy storage and electronic devices.
Estimate figure of merit (zT) of thermoelectric materials and understand the mechanism through appropriate descriptors.
Study thermodynamic and dynamical stability of a compound using proper parameters.
Analyse the theoretical understanding of vibrational spectra for layered as well bulk materials.
Effectively utilize Machine Learning algorithms to accelerate material discovery for energy applications.
Vibrational Spectroscopy: First-principle calculations of the phonon dispersion relations on the bulk and single layered materials have been studied. In addition to the vibrational spectroscopy, we also find avoided crossing or Landau quasi-degeneracy between longitudinal acoustics (LA) and low energetic transverse optical (TO) modes in both bulk forms of layered materials. The signature of such avoided crossing can be observed experimentally in the thermodynamic properties (such as specific heat and vibrational entropy). While specific heat and entropy both decrease at the temperature corresponding to the avoided crossing region, the specific heat value shows a kink in that region. The reason behind the avoided crossing has been analyzed using the concept of Born effective charge and dielectric tensor.
Electronic property: We have studied the bulk and layered structure that exhibits high carrier mobility together with a broad bandgap, which could be a promising candidate for nanoelectronics applications. Suitable mechanical flexibility permits strain-engineering in such layered structures to manifest carrier transport anisotropy. In fact, the lone pair associated with particular atoms leads to transport anisotropy in electron and hole mobility. These findings have been rationalized based on carrier scattering information and carrier effective mass derived from the electronic dispersion curve. All these findings point towards layered materials as an emerging candidate for power electronics applications.
Thermoelectric Property: I have worked on various materials, such as oxides, chalcogenides, etc. In fact, we design bulk and layered oxide material, which is dynamically and thermodynamically stable at ambient as well as at elevated temperatures. Furthermore, the lone pair associated with particular atoms introduce crystallographic anisotropy which strongly scatters low energetic heat-carrying acoustics phonons and consequently reduces lattice thermal conductivity. As a consequence of this bonding hierarchy and crystallographic anisotropy could be considered as a next-generation oxide-based thermoelectric (TE) material.
Energy storage: Materials with ultrahigh dielectric constants and a low value of dielectric loss are important for energy storage and electronic devices. Herein, a broadband colossal dielectric constant in a superionic halide with a low dielectric loss is presented. The maximum of ε′ reaches upto 6.4 × 108 at 300 K. The molecular dynamics simulation reveals the presence of ionic clusters with broad size distribution and the intercluster diffusion of particular atoms causes significant instantaneous charge separation and a consequent large fluctuation in the dipole moments. The fluctuating dipoles, in turn, result in the colossal dielectric constant in silver halides.
Hot-carrier Cooling Dynamics: We have worked on metal halide perovskite nanocrystals that have emerged as promising absorber material for the hot-carrier (HC) based solar cells. In fact, in line with the experimental study, we find that the HC cooling rate gets retarded due to charge localization at the interface of hetero-structure. Furthermore, a combination of an electron-phonon coupling model and first-principles calculations suggest a retarded relaxation through the Klemens channel due to an appearance of a large energy gap between the longitudinal optical (LO) and longitudinal acoustic (LA) phonon modes in the hetero-structure. Responsible for this is the localization of charge density near the hetero-junction which essentially leads to the up-conversion of LO modes to the higher energy and retards the HC relaxation rate which would be beneficial for the future of HC photovoltaics.
Machine Learning Algorithms: Currently, I am working to predict new advanced materials with better thermoelectric efficiency using the high-throughput approaches together with other functionalities. Furthermore, we are developing machine learning (ML) models to predict carrier transport parameters by analyzing the impact of the correct choice of descriptors and various algorithms, such as SVR, KRR, XGBoost, Random Forest and Decision tree algorithms.
Project title: Exploring carrier transport properties of superlattices for thermoelectric and optoelectronic applications through first-principles approach and Boltzmann transport theory
Funding agency: RUAS SEED-MONEY
Rs. 3.40 Lakhs (Principal Investigator)
Project title: Investigation of Janus monolayer for flexible transistor, thermoelectric and optoelectronic device applications using first-principles and data-driven machine learning approaches
Funding agency: SERB-DST
Rs. 37.15 Lakhs (Principal Investigator)