Phase-Dependent Excitonic Light Harvesting and Photovoltaic Limits in Monolayer Y2TeO2 MOenes

TL;DR

This study explores the phase-dependent electronic and excitonic properties of monolayer Y2TeO2 MOenes, revealing their stability, direct band gaps, and strong excitonic effects, with potential applications in photovoltaics.

Contribution

It provides the first comprehensive analysis of phase-dependent excitonic phenomena in Y2TeO2 monolayers using first-principles and many-body theories.

Findings

Both phases are dynamically and mechanically stable.

Direct band gaps in the near-infrared to visible range.

High exciton binding energies up to 152 meV.

Abstract

We investigate phase-dependent electronic and excitonic phenomena in monolayer Y2TeO2 MOenes in the 1T and 2H polymorphs using first-principles theory and an effective many-body framework. Phonon spectra and elastic stability criteria establish both phases as dynamically and mechanically stable. Quasiparticle band structures reveal direct gaps in the near-infrared to visible range, with gap values increasing systematically from semilocal to hybrid exchange treatments. Optical spectra computed using a tight-binding Bethe-Salpeter approach demonstrate pronounced excitonic resonances arising from reduced dimensionality and weak dielectric screening. The exciton binding energies reach 152 meV in the 1T phase and 126 meV in the 2H phase, reflecting enhanced quantum confinement in the structurally denser phase. Our results identify Y2TeO2monolayers as a rare class of stable, direct-gap MOenes with strong excitonic effects, providing a platform for exploring many-body physics in low-dimensional oxychalcogenide systems especially for photovoltaic applications.