  Transition metal dichalcogenide (TMDC) heterostructures have unique
properties that depend on the twisting angle and stacking order of two or more
monolayers. However, their practical applications are limited by the low
photoluminescence yield of interlayer excitons. This limits the use of layered
2D materials as a versatile platform for developing innovative optoelectronic
and spintronic devices. In this study, we report on the emission enhancement of
interlayer excitons in multilayered-stacked monolayers through the fabrication
of heterotrilayers consisting of WSe$_2$/WSe$_2$/MoSe$_2$ with differing twist
angles. Our results show that an additional WSe$_2$ monolayer introduces new
absorption pathways, leading to an improvement in the emission of interlayer
excitons by more than an order of magnitude. The emission boost is affected by
the twist angle, and we observe a tenfold increase in the heterotrilayer area
when there is a 44$^\circ$ angle between the WSe$_2$ and MoSe$_2$ materials, as
opposed to their heterobilayer counterparts. Furthermore, using density
functional theory, we identify the emergence of new carrier transfer pathways
in the three-layer sample which extends the current understanding of 2D
semiconducting heterostructures. In addition, our research provides a viable
way to significantly enhance the emission of interlayer excitons. The emission
enhancement of interlayer excitons is significant not only for studying the
fundamental properties of interlayer excitons, but also for enabling
optoelectronic applications that utilize engineered 2D quantum materials with
high luminescence yield.
