Atomistic manipulation of interfacial properties in HfN2/MoTe2 van der Waals heterostructure via strain and electric field for next generation multifunctional nanodevice and energy conversion

Abstract

This work sheds light on the intrinsic properties of HfN2 monolayer and its synergistic combination with MoTe2 for diverse applications in thermoelectricity, photovoltaics, piezotronics and digital/analog electronics using the state of art density functional theory. Using Boltzmann transport theory, a low lattice thermal conductivity of 0.49 Wm-1K-1 at 300 K along with high waste heat to electricity conversion efficiency (i.e., thermoelectric figure of merit, ZT = 2.28) is predicted for monolayer HfN2. On the other hand, a type-II van der Waals heterostructure (vdWH) is formed with 1H-MoTe2 monolayer, where low conduction band offset and direct band gap leads to high power conversion efficiency (PCE) of 21.44% in HfN2/MoTe2 excitonic solar cell. Moreover, it can be employed in designing multifunctional next-generation excitonic solar cells where electricity can be simultaneously generated from solar energy and the waste heat thrown out by the solar cell. The tunable electronic properties under perpendicular electric field highlights its application in both analog and digital electronics. The built-in electric field at the interface together with broken inversion symmetry along z-direction induces out-of-plane piezoelectricity (d33), which is in excellent agreement with experimental evidence (ACS Appl. Nano Mater.2020, 3, 11979–11986). d33 further increases 3.5 times under vertical compressive strain.