Theoretical Research On New Energy Materials And Devices With Wide Band Gap Van Der Waals Heterojunction

Wide band gap semiconductors have aroused widespread attention in both experimental research and industrial applications due to their unique physical and chemical properties.In recent years,the research on wide band gap semiconductor composite materials has become the focus of research.In this thesis,the application of wide band gap semiconductors and their composite materials in new energy materials and devices is studied based on the finite difference time domain algorithm and density functional theory.The main content of the article is as follows:(1)An optical absorber based on van der Waals material h-BN is proposed.Using finitedifference time-domain simulation,it is found that the absorber can obtain absorption spectrum above 95% in the range of 6490 to 7295 nm.Moreover,the proposed optical absorber can maintain excellent optical absorption performance over a wide range of incident angles.In order to elucidate the physical mechanism of the proposed absorber's efficient optical absorption performance,we studied the magnetic field distribution at different wavelengths in each h-BN optical absorber unit,and understood the optical absorption mechanism through the dispersion relationship.This research can find some important applications in thermal emitters and photovoltaic devices.(2)The application of 2D/2D Ga N/Si C based multilayer van der Waals heterojunction in photocatalytic decomposition of water for hydrogen production has been studied.We found that Bi-Ga N/Bi-Si C heterojunction has two properties that are beneficial to water decomposition: type-II heterojunction and suitable band gap(2.05 e V).This study proves that the number of Ga N and Si C layers plays an important role in the performance of Ga N/Si C heterojunctions.The type-II heterojunction is attributed to weak interlayer hybridization caused by multilayer Si C.The decrease of the band gap is due to the variation of lattice constant and the interlayer interaction.In addition,Bi-Ga N/Bi-Si C shows the highest visiblelight absorption coefficient on the whole,and exhibits appropriate band gap that straddles the redox potential of water splitting at p H = 7.This work suggests that the band structure can be regulated by adjusting the number of monolayer Ga N and Si C,which provides a theoretical guidance for experimental synthesis of Ga N/Si C heterojunctions for hydrogen production.