The quasiparticle approach making use of the GW approximation is suitable for modeling single particle excitations such as the addition or removal of an electron to/from the system. However, charge-neutral excitations that involve excitonic effects (electron-hole pair interaction) are not accounted for, as they require a two-particle Green's function in the context of many-body Green's functions theory. The corresponding equation-ofmotion can be expressed after some manipulation as a non-Hermitian eigenvalue problem known as Bethe-Salpeter equation (BSE)