First-Principles Study on Janus-Structured Sc₂CX₂/Sc₂CY₂ (X, Y = F, Cl, Br) Heterostructures for Solar Energy...

Two-dimensional van der Waals heterostructures have good application prospects in solar energy conversion due to their excellent optoelectronic performance. In this work, the electronic structures of Sc₂CF₂/Sc₂CCl₂, Sc₂CF₂/Sc₂CBr₂, and Sc₂CCl₂/Sc₂CBr₂ heterostructures, as well as their properties in photocatalysis and photovoltaics, have been comprehensively studied using the first-principles method. Firstly, both of the three thermodynamically and dynamically stable heterostructures are found to have type-II band alignment with band gap values of 0.58 eV, 0.78 eV, and 1.35 eV. Meanwhile, the photogenerated carriers in Sc₂CF₂/Sc₂CCl₂ and Sc₂CF₂/Sc₂CBr₂ heterostructures are predicated to follow the direct Z-scheme path, enabling their abilities for water splitting. As for the Sc₂CCl₂/Sc₂CBr₂ heterostructure, its photovoltaic conversion efficiency is estimated to be 20.78%. Significantly, the light absorption coefficients of Sc₂CF₂/Sc₂CCl₂, Sc₂CF₂/Sc₂CBr₂, and Sc₂CCl₂/Sc₂CBr₂ heterostructures are enhanced more than those of the corresponding monolayers. Moreover, biaxial strains have been observed to considerably tune the aforementioned properties of heterostructures. All the theoretical results presented in this work demonstrate the application potential of Sc₂CX₂/Sc₂CY₂ (X, Y = F, Cl, Br) heterostructures in photocatalysis and photovoltaics.