selected multifunctional 2d materials for energy conversion and devices plane wave dftbased approaches

Abstract

This thesis delves into a diverse array of advanced research fields, ranging from energy newlineconversion to futuristic electronic devices, by harnessing the novel properties and various newlineelectron degrees of freedom in atomically thin two-dimensional (2D) semiconductors and van newlineder Waals heterostructures. Utilizing first-principles density functional theory (DFT), the newlinethesis provides atomistic insights into the electronic, mechanical, piezoelectric, carrier newlinemobility, spintronic, valleytronic, ferroelectric, and ferromagnetic properties of selected 2D newlinematerials. newlineThe initial part of the thesis explores the relatively unexplored realm of nanoscale negative newlinepiezoelectricity in the dialkali metal monochalcogenide family, and#119872;and#8322;and#119883; (and#119872; = Na, K, Rb, or Cs; newlineand#119883; = O, S, Se, or Te) monolayers and their van der Waals (vdW) heterostructures 1 . The vdW newlineheterostructures derived from these semiconducting monolayers exhibit an anomalous newlinenegative out-of-plane piezoelectricity, with Naand#8322;Te/Csand#8322;S heterostructure demonstrating the newlinehighest negative piezoelectric coefficient (and#119889;and#8323;and#8323; = and#8722;39 pmVand#8315;¹). Additionally, the heterostructure newlineis highly responsive to external stimuli, such as electric field. A vertical electric field causes newlinethe band gap to gradually narrow and close, leading to a semiconducting-to-metallic newlinetransition at low electric fields of 0.31 and and#8722;0.33 V/Å. Consequently, low-power data storage newlinedevices could be efficiently realized through the application of small gate voltages. And, the newlinepronounced negative piezoelectric properties suggest strong potential for applications in newlinepiezotronic energy harvesting devices and advanced electronic technologies. newlineThe subsequent part emphasizes the importance of accurately determining carrier mobility to newlineevaluate the performance of electronic devices, focuses on the transport properties of highly newlineanisotropic, semiconducting 2D transition metal trichalcogenide (TMTC) monolayers, and#119872;and#119883; 3 newline(and#119872; = Ti, Zr or Hf; and#119883; = S or Se) 2 . The integration of the Boltzmann Transport Equation newline(BTE) with DFT markedly enhances