Enhanced visible light absorption and carrier mobility in the type-II Bi2C3/GeTe van der Waals heterostructure: a first-principles study.

Vertically stacking distinct two-dimensional (2D) materials into van der Waals (vdW) heterostructures has proven to be an effective paradigm for overcoming single-layer limitations and boosting optoelectronic capabilities. In this study, we employ first-principles calculations to systematically probe the structural, electronic, transport, and optical characteristics of the Bi2C3/GeTe heterostructure. Our findings confirm the energetic stability of this heterosystem, with weak vdW forces governing the interlayer coupling. Notably, the formation of the interface enhances in-plane stiffness, thereby improving mechanical robustness. Furthermore, the heterostructure displays a type-II band alignment, facilitating the spatial separation of photogenerated electron-hole pairs. Additionally, the Bi2C3/GeTe heterostructure demonstrates a reduced band gap compared to its constituent monolayers, leading to improved visible-light responsiveness. Remarkably, the optical absorption spectrum shows a significantly broadened absorption range and enhanced absorption intensity in the visible region. The maximum absorption coefficient reaches up to 3.50 × 105 cm-1. In addition, the Bi2C3/GeTe heterostructure exhibits remarkably high carrier mobilities for both electrons and holes, indicating excellent charge transport capability. This combination of superior carrier mobility and efficient charge separation further underscores its potential for high-performance applications.