Research On Photoelectric Properties And Regulation Of Two-dimensional Carbon-based Van Der Waals Heterojunction

Due to its unique geometry and tunable electronic properties,two-dimensional(2D)C_xN_y shows broad application prospects in photocatalysis.Up to now,there are few researches on van der Waals heterojunction of carbon-based materials,and its application in devices is not mature.Hence,it is vital to explore its basic properties and its application prospect in photoelectric devices.In this paper,the basic electronic properties of C₃N and C₂N are studied based on the first principles,and the two-dimensional van der Waals heterojunction is constructed with?-antimonene and Janus Ga₂SeTe(Ga₂STe,Ga₂SeS)respectively.The electronic properties,band regulation and optical properties of C₃N/?-antimonene and C₂N/Ga₂SeTe(Ga₂STe,Ga₂SeS)heterojunctions are studied.The research achievements of this paper are as follows:(1)The regulation mechanism of electric field and vertical strain on the electronic properties of C₃N/?-antimonene heterojunction and the good photoelectric properties of the heterojunction are revealed.The results show that the heterojunction has an intrinsic type-?band arrangement,which can effectively inhibit the recombination of photon-generated carriers,which is very important for the fabrication of photoelectric nanodevices with good performance.In addition,vertical strain and applied electric field can change the band gap and band arrangement of the heterojunction,and may make it appear metallic.Meanwhile,the heterojunction exhibits high absorption coefficients(?10~5cm^-1)in both blue and near infrared light,and the absorption efficiency can be significantly improved by biaxial strain and vertical strain,and the photocurrent density can reach up to 3.6 mA/cm~2,which is of great significance for the application of photocatalysis.(2)The effect of Janus asymmetry on the electron properties of C₂N/Janus Ga₂SeTe(Ga₂STe,Ga₂SeS)heterojunction are revealed,and the regulation mechanism of biaxial strain on the electron structure of the heterojunction is explored.The results show that different types of atoms on the interface of heterojunction lead to different energy band arrangement,which is beneficial to the application of heterojunction in different fields.Biaxial strain can effectively regulate the band gap of heterojunction and transform it into type-?band arrangement,which is very important for enhancing its catalytic performance in photowater reaction.(3)The feasibility of C₂N/Ga₂SeTe(Ga₂STe,Ga₂SeS)heterojunction in the field of photocatalytic water decomposition are explored.It is found that the three heterojunctions have good photocatalytic performance of water decomposition by calculating the band edge position.The oxidation(reduction)capacity of the heterojunction can be changed by biaxial strain.Under biaxial strain,the optical absorption wavelength range of the heterojunction is widened and the optical absorption coefficient is obviously increased.In addition,the photoelectric conversion efficiency(PCE)of C₂N/Ga₂SeTe(Ga₂STe)heterojunction can reach 11.2%and 7.2%,respectively,by applying biaxial strain.These results provide theoretical guidance for the preparation of novel photocatalytic catalysts for water decomposition.