Two-Dimensional Functionalized MM’CT₂ (M = Sc; M’ = Y; T = Br, Cl, F, H, I, O, OH, S, Se, Te) MXene Monolayers for Photovoltaic Applications

Abstract

We investigate the structural, optoelectronic, and excitonic properties of Janus bimetal MXene monolayers with the formula MM’CT2 (M = Sc; M’ = Y; T = Br, Cl, F, H, I, O, OH, S, Se, Te) using first-principles calculations combined with a semiempirical MLWF-TB+BSE approach. A developed workflow for a computational screening procedure was employed to assess their stability and optoelectronic performance. Excitonic and photovoltaic properties were computed using our group’s WanTiBEXOS code, an open-source tool under active development and available under the GPL license. Among the 11 candidate monolayers, six were structurally stable semiconductors. Electronic band structure calculations indicate an indirect semiconducting nature for the majority of the compounds, with band gaps lying in the range of 0.96 eV to 1.90 eV. The linear optical response reveals a strong optical absorption in the infrared and visible regions, highlighting their potential for light-harvesting applications. Additionally, the calculated exciton binding energies range from 187 to 520 meV and are consistent with typical 2D materials, demonstrating significant excitonic effects for an accurate description of the optical band gap, a crucial property in the energy conversion process. The estimated power conversion efficiency, evaluated through the Shockley–Queisser limit, lies between 23.44% and 32.55%, at spectroscopy-limited maximum efficiency approach, it lies between 16.48% and 28.82%, when quasi-particle effects are considered, establishing these Janus MM’CT2 MXenes as potential contenders for next-generation photovoltaic technologies.