Microscopic Theory of Exciton-Exciton Annihilation in Two-Dimensional Semiconductors

TL;DR

This paper develops a first-principles many-body theory to accurately describe exciton-exciton annihilation in 2D semiconductors, providing insights into its role as a loss mechanism in optoelectronic devices.

Contribution

It introduces a material-realistic, first-principles theoretical framework for exciton-exciton annihilation in 2D materials, surpassing previous effective models.

Findings

EEA coefficient in monolayer MoS₂ is about 10^{-3} cm²/s at room temperature.

Carrier losses are often dominated by defect-assisted scattering rather than EEA.

The theory enables quantification of intrinsic EEA efficiency in various 2D materials.

Abstract

Auger-like exciton-exciton annihilation (EEA) is considered the key fundamental limitation to quantum yield in devices based on excitons in two-dimensional (2d) materials. Since it is challenging to experimentally disentangle EEA from competing processes, guidance of a quantitative theory is highly desirable. The very nature of EEA requires a material-realistic description that is not available to date. We present a many-body theory of EEA based on first-principle band structures and Coulomb interaction matrix elements that goes beyond an effective bosonic picture. Applying our theory to monolayer MoS$_2$ encapsulated in hexagonal BN, we obtain an EEA coefficient in the order of $10^{-3}$ cm$^{2}$s$^{-1}$ at room temperature, suggesting that carrier losses are often dominated by other processes, such as defect-assisted scattering. Our studies open a perspective to quantify the efficiency of intrinsic EEA processes in various 2d materials in the focus of modern materials research.