Thermoelectric Properties Of Two-dimensional ZrI₂ Monolayer

The increasing energy consumption and increasingly serious environmental problems have caused wide public concern in recent years.To overcome the coming energy crisis,it is of great significance to explore sustainable and ecologically friendly energy resources.Hence the surge in interest in thermoelectric materials,which can convert waste heat directly into electricity using solid-state devices without causing any pollution to the environment.This is one of the effective ways to ease the energy crisis and reduce the environmental pollution caused by fossil fuels.While power factor PF and thermoelectric merit z T can effectively measure the thermoelectric performance of a material.Materials with high thermoelectric merit have high thermoelectric merit and can have high thermoelectric conversion efficiency.At present,an efficient thermoelectric device can be made by two methods:one is to find new materials with high thermoelectricity,and the other is to improve the thermoelectric properties of known thermoelectric materials through a series of optimization measures.Due to the rapid development of synthesis and stripping techniques in experiments,a large number of two-dimensional layered structures have been synthesized,and some two-dimensional layered structures have been found to have good thermoelectric properties theoretically,such as transition metal dihalide Zr S₂,chalcogenide Sn Se,metal-coated layered material Tl₂O,etc.In addition,with the in-depth study of thermoelectric materials,people also put forward a lot of strategies to optimize thermoelectric materials.Such as chemical functionalization,mechanical strain,heterostructure and structural defects,these strategies have achieved good results and increased the thermoelectric properties of known materials.With the improvement of density functional theory and the rapid development of computer performance,it is indispensable to find or design thermoelectric materials with superior performance purposefully through the theory,and then rely on the theory to guide the experiment to design these thermoelectric materials.Compared with the high cost of experiments,theoretical simulation computing is very approachable.Nowadays,with the improvement of various theories and the rapid development of computers,the results of theoretical calculations are more and more consistent with the results of experiments.Therefore,guiding experiments from theories has become an important part of the field of materials science.In this paper,two dimensional thermoelectric materials are found and optimized by means of density functional theory.They not only have high power factor,but also good thermoelectric value,which provides a reference for experimental design and searching for thermoelectric materials with superior performance.The main research content of this paper includes the following aspects:Theoretical study on the superior thermoelectric properties of n-type doped2H-ZrI₂monolayer.We systematically evaluate the thermoelectric properties of2H-ZrI₂monolayer by first principles calculations and semi-classical Boltzmann transport theory.The stability of the structure and the feasibility of the experimental preparation were investigated,and the lattice thermal conductivity is found to be 6.69m W/m K at 900 K.The four-phonon scattering is found to exert a minor effect on the lattice thermal conductivity of the monolayer.In addition,considerable power factors PF can be achieved,up to 147.89 m W/m K²,due to the conduction valley degeneracy near the Fermi level.At certain experimentally achievable electron doping concentrations,these transport coefficients eventually yield a significantly optimal n-type z T value of up to 3.57 at 900 K.Our study demonstrates the potential application of monolayer 2H-ZrI₂in high temperature thermoelectric devices.