Harnessing Linear and Nonlinear Optical Responses in Ferroelectric LaMoN$_3$ for Enhanced Photovoltaic Efficiency

TL;DR

This study uses first-principles calculations to explore how pressure influences the optical and photovoltaic properties of ferroelectric LaMoN$_3$, revealing optimal conditions for enhanced solar energy conversion.

Contribution

It provides a comprehensive analysis of LaMoN$_3$'s phase stability, optical responses, and photovoltaic efficiency under pressure, highlighting pressure as a tuning parameter for device optimization.

Findings

LaMoN$_3$ remains stable up to 40 GPa with a decreasing bandgap.

Pressure enhances the SLME and reduces exciton binding energy.

Photovoltaic efficiency peaks near 15 GPa due to nonlinear optical response.

Abstract

Nitride perovskites are an emerging class of materials predicted to exhibit diverse functional properties, yet remain underexplored due to synthesis challenges of oxygen-free nitrides. Recently, LaMoN$_3$ has been reported as an oxygen-free nitride perovskite with polar symmetry, exhibiting excellent dynamic stability and ferroelectric properties under moderate pressure. However, its phase stability, linear and non-linear optical response, excitonic and polaronic behavior, and efficiency under high pressure remain unexplored. Applying pressure enables systematic tuning of the electronic structure properties, thereby facilitating the identification of phases optimized for either linear or nonlinear optical responses. Therefore, in this work, we systematically investigate these properties of LaMoN$_3$ up to 40 GPa using first-principles methods, including density functional theory, density functional perturbation theory, many-body perturbation theory (namely G$_0$W$_0$ and BSE), and tight binding approximation model. Our study shows that LaMoN$_3$ remains dynamically stable and retains its single-phase structure up to 40 GPa. The compound exhibits an indirect bandgap that decreases from 2.17 eV (0 GPa) to 1.45 eV (40 GPa) at the G$_0$W$_0$@PBE level. Using the BSE, we find that pressure enhances the SLME while lowering the exciton binding energy, both favorable for photovoltaic applications. The bulk photovoltaic efficiency trend with pressure mimics the behavior of the shift current density J$_SC$ , peaking near 15 GPa before declining at higher pressures due to a diminished nonlinear shift current response. These results highlight pressure-tuned regimes to enhance photovoltaic performance. We thereby propose multi-junction device, combining absorber layers optimized for linear and nonlinear optical currents, together boosting solar energy conversion through complementary mechanisms.