Abstract
Vertically stacked van der Waals heterostructures constitute a promising platform for providing tailored band alignment with enhanced excitonic systems. Here, we report observations of neutral and charged interlayer excitons in trilayer WSe2–MoSe2–WSe2 van der Waals heterostructures and their dynamics. The addition of a WSe2 layer in the trilayer leads to significantly higher photoluminescence quantum yields and tunable spectral resonance compared to its bilayer heterostructures at cryogenic temperatures. The observed enhancement in the photoluminescence quantum yield is due to significantly larger electron–hole overlap and higher light absorbance in the trilayer heterostructure, supported via first-principles pseudopotential calculations based on spin-polarized density functional theory. We further uncover the temperature- and power-dependence, as well as time-resolved photoluminescence of the trilayer heterostructure interlayer neutral excitons and trions. Our study elucidates the prospects of manipulating light emission from interlayer excitons and designing atomic heterostructures from first-principles for optoelectronics.
Highlights
In two-dimensional (2D) materials, Coulomb-induced electronic states of excitons have been examined as a platform to understand many-body carrier–carrier interactions. These excitonic interactions dominate in layered materials due to quantum confinement and reduced dielectric screening. 2D atomic crystals of transition metal dichalcogenides (TMDs) have provided new opportunities in the studies of single-exciton single-photon interactions, spin–orbit coupling, ultrafast dynamics, and nanoelectronic devices.[1–22]
Layer-by-layer stacking of TMDs-based van der Waals heterostructures has recently captured the attention of the scientific community where the tailored band alignment with diverse 2D materials can be achieved via advanced 2D growth and transfer techniques.[23–28]
These interlayer excitons exhibit rich physics in TMDs-based van der Waals (vdWs) heterostructures due to the novel atomic granularity control through layer-by-layer stacking and the chiral properties of quantum electronic states.[8,31,32]
Summary
In two-dimensional (2D) materials, Coulomb-induced electronic states of excitons have been examined as a platform to understand many-body carrier–carrier interactions. (An example comparison of the trilayer to the bilayer is point We note that the interlayer radiative recombination channels—in both the neutral exciton and trion—may involve the processes of optical phonons in order to conserve momentum in the band-to-band transition by optical phonon absorption and phonon emission This is especially the case for the trion which has approximately two times larger full-width half-maximum (FWHM) than the neutral exciton (detailed in Supplementary Figure S4) and has a stronger thermal dependence.
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