Substitutional doping-induced tunable van der Waals heterostructures of X-WSe₂/Ti₂CO₂ in optoelectronic properties: A first-principles study

This study constructed the X-WSe₂/Ti₂CO₂ vdW-HS and explored the doping effects of transition metal elements X (X being V, Nb, Ta, Mo, or Tc) on the W or Se sites of WSe₂ in the heterojunction. First-principles calculations revealed that all structures possess stability, with those doped at the W site mostly exhibiting metallic properties; whereas those doped at the Se site are all semiconductors, and for elements in the same period, Nb, Mo, and Tc doping reduced the bandgap from 0.4 eV to 0.32 eV–0.213 eV. The order of interlayer charge transfer in the heterojunction is Tc > Mo > V > Ta > Nb (W site) and Ta > Nb > Mo > V > Tc (Se site). The optical absorption coefficient in the visible light range can reach as high as 4.8 × 10⁵ cm⁻¹ (Mo-doped Se). The main reason for these phenomena is that the doping of X has different filling effects on the CB and VB of the system, causing shifts in the E_f and atomic orbitals, thereby achieving regulation of the heterojunction properties. These findings provide a theoretical basis for the design and optimization of high-performance optoelectronic devices.