Hexagonal boron nitride: optical properties in the deep ultraviolet.

We review the recent advance in the understanding of the optoelectronic properties of hexagonal boron nitride (hBN) in the deep ultraviolet. The comparison between bulk hBN and monolayer hBN highlights some of theirmajor differences such the bandgap nature, the excitonic binding energy and the phononassisted broadening of the excitonic lines. Perspectives point out the relevance of addressing the regime of hBN samples made of a very few number of monolayers, including twisted hBN monolayers in the context of twistronics. [ABSTRACT FROM AUTHOR]