Defect-Induced Ultrafast Nonadiabatic Electron-Hole Recombination Process in PtSe₂ Monolayer

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Materials Science

Background:

• Defects are inherent in two-dimensional (2D) materials, influencing their electronic and optical properties.
• Understanding defect dynamics is crucial for optimizing 2D material applications.

Purpose of the Study:

• Investigate the impact of native point defects on nonradiative recombination in PtSe2 monolayers.
• Explain the slow response observed in PtSe2-based photodetectors.

Main Methods:

• First-principles calculations were employed to model PtSe2 monolayers with and without defects.
• Analysis of defect states, electronic band structure, and vibrational modes.

Main Results:

• Selenium antisite defects introduce shallow p-type states.
• Selenium vacancies create shallow and deep n-type defect states.
• Defect states strongly couple to the valence band maximum, enhancing the Eg vibrational mode.
• Increased non-adiabatic coupling accelerates electron-hole recombination.

Conclusions:

• Native point defects in PtSe2 significantly enhance non-adiabatic coupling.
• This leads to accelerated nonradiative recombination, explaining the slow response in PtSe2 photodetectors.