Study On Sensing Characteristics And Thermodynamic Properties Of Black Phosphorene And Black Phosphorene-like

The two-dimensional material black phosphorene has attracted the research interest of domestic and foreign researchers with its excellent electrical and optical properties,since it was successfully prepared in2014.Black phosphorene has electrical characteristics such as large mobility,high on/off ratio and adjustable direct band gap,making it widely used in daily life and scientific research.The two-dimensional black phosphorene-like material has a structure similar to that of black phosphorene,and its unique electrical properties make it also very important for research.Black phosphorene and black phosphorene-like materials are two-dimensional structural materials,and their large surface/volume ratio have huge advantages in gas adsorption.In this paper,the VASP（Vienna Ab-initio Software Package）software package based on density functional theory is used to calculate the adsorption characteristics of black phosphorene-like materials GeS,GeSe,SnS and SnSe,and study the application of few-layer black phosphorene stacking structure in thin-film solar cells.The VASP+Phonopy software package is used to calculate the thermodynamic properties of black phosphorene.The adsorption of H₂,N₂,O_2,CO,NO,CO₂,NO₂,H₂O,H₂S,SO₂,NH₃ and SO₃ on black phosphorene-like materials and the changes in the electrical properties of the adsorption system before and after the gas adsorption were investigated.The main research contents of this paper and the research results obtained are as follows:（1）Firstly,the adsorption properties of black phosphorene-like materials GeS,GeSe,SnS and SnSe to gases H₂,N₂,O₂,CO,NO,CO₂,NO₂,H₂O,H₂S,SO₂,NH₃ and SO₃ are studied.According to the adsorption energy,transfer charge and the electron gas distribution between the molecule and the substrate,the adsorption type is divided into physical adsorption and chemical adsorption.The adsorption of H₂,N₂,CO,CO₂,H₂O,H₂S and NH₃ on GeS,GeSe,SnS and SnSe are all physical adsorption.In physical adsorption,the adsorption energy is less than 0.41e V,the transfer charge is small,and the interaction between the substrate and the gas is weak.So black phosphorene-like materials are not suitable for sensor materials for these gases.In chemical adsorption,the adsorption of the three gases NO₂,SO₂ and NO all change the electrical properties of the substrate.Among them,the adsorption of NO causes the spin polarization of GeS,GeSe,SnS and SnSe,introducing magnetic moments of 0.999,0.999,1 and 1μ_B respectively;the adsorption of SO₂ reduces the band gaps of GeS,GeSe,SnS and SnSe;the NO₂ adsorption SnS system and the NO₂ and SO₃adsorption SnSe system also produce the transformation of P-type semiconductor.In addition,after adsorbing NO₂,SO₂ and NO gases,the changes in the I-V characteristics of GeS,GeSe,SnS and SnSe are observed.Therefore,the black phosphorene-like materials GeS,GeSe,SnS and SnSe have research value as NO₂,SO₂ and NO gas sensor materials.（2）The structure of bilayer stacking b P-like materials GeS,GeSe,SnS and SnSe are studied,both translation and twist stacking.Through repeated modeling and optimization,the lowest energy states of the bilayer stacking structures are found out.The stable and metastable states are AB,AD and AA,Aδstructure respectively.Their electrical properties were simply analyzed.Then pairwise combination of these two structures used as thin film solar-cell materials,according to the band gap of the donor and the minimum conduction band difference between the acceptor and the donor.Their power conversion efficiency is also calculated.Among them,twist-AD-stacked bilayer GeS combined with translate-AD-stacked bilayer SnSe,the translate-AD-stacked bilayer SnSe combined with twist-AB-stacked bilayer GeS,translate-AA-stacked bilayer GeSe combined with the twist-AD-stacked bilayer SnSe and translate-AB-stacked bilayer SnSe,respectively show high power conversion efficiency of solar cells,as high as 23%.All of these results show that the bilayer b P-like will have great potential in the application of thin-film solar cells in the future.（3）Finally,the thermodynamic properties of black phosphorene are studied,and the calculation method of Phonopy+QHA is used to reduce the amount of calculation.Thermodynamic quantities such as Helmholtz free energy,entropy,specific heat capacity and thermal expansion coefficient of black phosphorene have been calculated.The anisotropy of thermal expansion coefficient is consistent with other research results,which provides a reference for the application of black phosphorene in thermoelectric materials.