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

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 MoS2 encapsulated in hexagonal BN, we obtain an EEA coefficient in the order of 10 −3 cm 2 s −1 at room temperature, suggesting that exciton annihilation is 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.c/v k is the energy of a carrier with momentum k in a conduction/valence band, and V λ,ν,ν ,λ k,k ,k +q,k−q are Coulomb interaction matrix elements. The crystal area is denoted by A. Augerlike EEA emerges as a higher-order carrier-carrier interaction process within the dynamics of microscopic exciton populations, which are described by two-particle

Dielectric Engineering for Manipulating Exciton Transport in Semiconductor Monolayers

“…We note that such a huge variance in the Auger recombination rate cannot be explained by the change of the Coulomb-mediated Auger scattering. 15,54 Thus, we infer that the decisive factor is the change of the defect-assisted Auger recombination rate due to various dielectric disorders. In a defective system, the exciton detrapping rate decreases (ratio of excitons being trapped increases) with increased trap depth.…”