First-principles many-body comparative study of Bi2Se3 crystal: A promising candidate for broadband photodetector

In this work, we present a theoretical investigation on the structural, electronic and optical properties of Bi2Se3 via density functional theory (DFT) approach in conjunction with a many-body perturbation theory (MBPT) formalism. It was found that inclusion of van der Waals (vdW) correction reproduce experimental interlayer distances, lattice parameters and atomic coordinates of Bi2Se3 material. Also, band structure calculations show that G0W0 correction leads to a band gap closer to the experiment. On the other hand, excitonic effects and optical properties, namely, imaginary and real parts of dielectric function, refractive index, absorption coefficient, extinction coefficient, reflectivity, electron energy loss function and optical conductivity are investigated using Bethe-Salpeter equation (BSE) approach. Our first time reported results of Bi2Se3 with inclusion of electron-hole interaction show a good agreement with the available experimental measurements. The obtained results of the exciton energy show that the title material can absorb a photon within infrared wavelengths.