  Realizing direct-bandgap quantum dots working within the deep-ultraviolet
frequency is highly desired for electro-optical and biomedical applications
while remaining challenging. In this work, we combine the first-principles
many-body perturbation theory and effective Hamiltonian approximation to
propose the realization of arrays of deep-ultraviolet excitonic quantum dots in
twisted bilayer hexagonal boron nitride. The effective quantum confinement of
excitons can reach ~400 meV within small twisting angles, which is about four
times larger than those observed in twisted semiconducting transitional metal
dichalcogenides. Especially because of enhanced electron-hole attraction, those
excitons will accumulate via the so-call exciton funnel effect to the
direct-bandgap regime, giving the possibility to better luminescence
performance and manipulating coherent arrays of deep-ultraviolet quantum dots.
