Preparation And Properties Of BaSi₂ Thin Film Battery Devices By Magnetron Sputtering

Due to its advantages of low cost,cleanliness,renewable and environmental protection,solar cells have become one of the main ways to solve the shortage of energy demand.The silicide semiconductor material barium disilicide(BaSi₂)is composed of abundant and non-toxic Baelements and Si elements.This material has a band gap of1.3 eV suitable for converting sunlight,and has more than 3×10⁴ cm^-1 in the visible region.The high optical absorption coefficient,the minority carrier lifetime of intrinsic BaSi₂ is about 10?s,and the minority carrier diffusion length exceeds 10?m,all these parameters indicate that BaSi₂ material is a potential thin-film solar cell material.The research and development of solar cell devices based on BaSi₂ thin film is still in its infancy.This paper focuses on this goal,and firstly designs,simulates and discusses the device based on BaSi₂ thin film.After that,the growth of BaSi₂ thin film was carried out on the low-resistance Si substrate,and the Schottky device based on BaSi₂ was preliminarily prepared,and good rectification characteristics were obtained.The specific work is as follows:(1)The device structures of n-BaSi₂/p-Si heterojunction and p⁺-BaSi₂/n-BaSi₂homojunction cell are designed,and the cell device is simulated by SCAPS-1D simulation software.The results show that the theoretical efficiency of the n-BaSi₂/p-Si heterojunction cell device is only close to 12%due to the large energy band offset between Si and BaSi₂,which affects the transport of minority carriers.;For the p⁺-BaSi₂/n-BaSi₂ homojunction,the theoretical conversion efficiency over 25%was obtained by optimizing the carrier concentration of the window layer and the absorber layer,the thickness of the window layer,the thickness of the absorber layer and the defect concentration of the absorber layer;At the same time,we also discussed the influence of the n⁺-Si substrate on the homojunction performance,and pointed out that when the n⁺-BaSi₂ buffer layer was inserted between the n⁺-Si substrate and the n-BaSi₂absorber layer,the formation of the structure of p⁺-BaSi₂/n⁺-BaSi₂/n⁺-Si can greatly reduce the influence of the substrate on the battery performance.(2)For the growth of BaSi₂ thin films on low-resistance Si substrates,four different low-resistance Si substrates were used,namely B-doped p-type Si substrates(B/p-Si)and Sb,As,and Ph-doped Si substrates.Miscellaneous n-type Si substrates(Sb/n-Si,As/n-Si,Ph/n-Si),And re-optimized growth conditions such as seed layer,substrate temperature,Ba/Si ratio,etc.,to obtain BaSi₂ thin films with high crystalline quality and good surface morphology;Then,the diffusion of dopant atoms in low-resistance substrates during film growth is discussed and the diffusion mechanism is analyzed to provide reference for device fabrication.(3)Through the preparation of Al/BaSi₂ Schottky junction and the study of ? characteristics,the influence of doping atoms in the substrate on the properties of the film is further confirmed.We found that the entry of As and Sb is more likely to lead to the current carrying of n-BaSi₂ While B and Ph are easy to diffuse,they are difficult to activate and have little effect on conductivity type and carrier concentration;Finally,the BaSi₂ film was passivated by depositing a-Si:H on the surface of BaSi₂ by PECVD,which significantly improved the photoelectric response performance of the film.These works have an important promotion and reference for the subsequent design and fabrication of solar cells based on BaSi₂ thin films.