Enhanced excitonic features in an anisotropic ReS2/WSe2 heterostructure

Abstract

Two-dimensional (2D) semiconductors have opened new horizons for future optoelectronic applications through efficient light–matter and many-body interactions at quantum level. Anisotropic 2D materials like rhenium disulphide (ReS₂) present a new class of materials with polarized excitonic resonances. Here, we demonstrate a WSe₂/ReS₂ heterostructure which exhibits a significant photoluminescence quenching at room temperature as well as at low temperatures. This indicates an efficient charge transfer due to the electron–hole exchange interaction. The band alignment of two materials suggests that electrons optically injected into WSe₂ are transferred to ReS₂. Polarization resolved luminescence measurements reveal two additional polarization-sensitive exciton peaks in ReS₂ in addition to the two conventional exciton resonances X₁ and X₂. Furthermore, for ReS₂ we observe two charged excitons (trions) with binding energies of 18 meV and 15 meV, respectively. The bi-excitons of WSe₂ become polarization sensitive and inherit polarizing properties from the underlying ReS₂ layers, which act as patterned substrates for top layer. Overall, our findings provide a better understanding of optical signatures in 2D anisotropic materials.