During the last decade, novel two-dimensional (2D) semiconducting materials have been synthesized and characterised. As a result, there have been several theoretical and experimental proposals to incorporate 2D materials for designing next generation electronic and optoelectronic devices. In particular, it has been demonstrated that light absorption in phosphorus-based monolayers can span the whole visible spectrum, suggesting they could be used for optolectronic applications. A key ingredient for optical applications is the presence of excitons and their subsequent diffusion along a donor material. This is influenced by the character of the different excitations taking place, as well as, the exciton binding energy. At the same time the anisotropic character of black phosphorus can give rise to interesting optical responses depending on the polarization, and even more so at the edges of the sample. This could interesting phenomena such as unusual thermal conductivity at the edges of the material compared to the bulk.

Therefore, In this work we use accurate density functional theory calculations to probe the optical response of different phosphorus allotropes. First, by means of GW-BSE methodology to we elucidate the most important optical transitions, exciton energy spectrum as well as exciton extension in di fferent types of phosphorene materials. In addition, we solve the Schrodinger equation for different 2D screened potentials in a hydrogenic model and estimate the 2D exciton energy levels and radius extension. Finally, we also study the Raman spectrum on the edges of black phosphorene to show the presence of forbidden Raman modes seen in experiments, which arise from edge reconstruction.