First-principles Study On The Eletronic Structure Of ZnSiP₂ Material

Multi-junction stacked solar cells have the advantages of wide absorption spectrum and low heat loss,which are one of the development directions of high-efficiency solar cells.The band gap of the Ⅱ-Ⅳ-Ⅴ2 group material ZnSiP2 is about 2.0 eV,and its lattice mismatch rate with Si is only 0.5%.ZnSiP2 is also suitable for heteroepitaxial growth so that can be used to manufacture top cells for silicon-based multi-junction stacked solar cells.At present,the research on ZnSiP2 materials is inadequate,and the parameters such as electron affinity have not been reported.In addition,due to the high volatility of Zn and P,Si-rich phenomenon is easy to occur in ZnSiP2 material,and it is difficult to prepare ZnSiP2 material that meet the ideal stoichiometric ratio.However,the relevant properties of Si-rich ZnSiP2 material have not been reported.These problems limit the further development and utilization of ZnSiP2 material.In this study,by utilizing the first-principles calculation software VASP,the crystal structure and band structure of ZnSiP2 were analyzed and the properties parameters such as electron affinity and effective mass were obtained.The band structure calculated by HSE06 hybrid functional method with higher precision.At the same time,the crystal structure,band structure and stability of ZnSiP2 materials with different Si contents were analyzed,which provide a reference for the development of ZnSiP2 solar cells.The main calculation results are as follows:1.Using the generalized gradient approximation(GGA)within the PBE density functional method,the lattice constant of ZnSiP2 is calculated to be 5.420 A.The band gap of ZnSiP2 calculated by HSE06 hybrid functional method is 2.048 eV,the deviation with the reported experimental result is 1.89%.On this basis,the calculated electron affinity of ZnSiP2 is 3.056 eV,the effective mass of electrons and holes in the Γ-M direction is 0.406mo and 0.849m0,and the effective mass of electrons and holes in the Γ-N direction is 0.262m0 and 0.43 7m0.2.The properties of Si-rich ZnSiP2 materials in which Si atoms replace Zn atoms,P atoms,and Zn&P double atoms are studied.The results show that when the Si content increases from 25%to 37.5%,the Zn content decreases from 25%to 18.75%,and the P content decreases from 50%to 43.75%,the lattice mismatch rate between ZnSiP2 and Si is less than 1.23%.Its band gap decreases with Si content increasing,and the variation range is 2.05 eV to 0.63 eV.3.The formation energy calculation results of Si-rich ZnSiP2 materials show that:the formation energy of Si atoms replace P atoms is less than 0 eV/atom,the formation energy of Si atoms replace Zn atoms is more than 0 eV/atom.The material formed by Si atoms replace P atoms is more stable than Si atoms replace Zn atoms.