Research On The Design And Photoelectric Properties Of Two-dimensional Heterojunction Based On Graphite Phase Carbon Nitride

Two-dimensional materials have received widespread attention from researchers because of their layered crystal structure,extreme quantum confinement effect,and unique physical and chemical properties.Researchers have explored the application of two-dimensional materials in the fields of photocatalysis,optical energy storage,spintronics,etc.g-C₃N₄,group III chalcogenide and graphene are typical two-dimensional materials.This thesis uses first-principles to construct related two-dimensional material heterojunctions based on the existing research background of g-C₃N₄,and explores the electronic transport,optical response and photocatalytic properties of materials.The heterojunction in this thesis was constructed using different KNbO₃ surfaces and g-C₃N₄,and the energy band structure and electron transfer process of the composite material were analyzed.There is a significant red shift in the light absorption of the heterojunctions,and the absorption edge moves toward the visible light region.Among them,the KO/g-CN heterostructure composed by the KO surface of KNbO₃ and g-C₃N₄ monolayer constitutes an obvious type II heterojunction,which realizes effective separation of photogenerated electrons and holes.The experimental results and the photocatalytic process of KNbO₃/g-C₃N₄ composite materials have been systematically explained for the first time.This paper also theoretically predicts the monolayer material of Group III chalcogenide and studies the photocatalytic performance and mechanism of GaX?X=S,Se?/g-C₃N₄ heterojunction.When the S or Se atoms of the GaS and GaSe monolayers correspond to the ring center position of g-C₃N₄,the structure of the constructed heterojunction is the most stable.The electric field and stress are used to modulate the properties of the heterostructure,and the similarities and differences of the properties of the GaS/g-C₃N₄ and GaSe/g-C₃N₄ composites are compared.Finally,the properties of related materials GaSSe are studied.The GaSSe monolayer was combined with graphene,and the electronic structure and interface contact of the GaSSe/graphene heterostructure were discussed.After GaSSe is in contact with graphene,the graphene band gap can be effectively opened at the Dirac point,and the Dirac cone remains good.By applying an appropriate vertical pressure and external electric field to the heterostructure,the contact interface can achieve an effective conversion between p-type and n-type Schottky contat,or even a Schottky contact to ohmic contact.With the increase of biaxial tensile stress and compressive stress,the light absorption extreme point of the material showed a tendency to move to the lower right and upper left respectively.These findings predict the huge potential of composite materials in the field of next-generation optoelectronic devices and are of great significance for the design of nanoelectronic devices.