In this study, the RHF and B3LYP methods with cc-pVDZ basis set have been used to investigate the non-linear optical (NLO), electronic, optoelectronic and thermodynamic properties of bis (ethylenedithio) tetrathiafulvalene and its chlorine and bromine derivatives. The results show that the undoped molecule denoted BEDT-TTF or ET (Eg =3.88 eV) and its derivatives are semi-conductors materials. However, one of them, Br4ET molecule doped with bromine, considerably improves its energy band gap Eg =2.88 eV is less than 3 eV, which makes more ineresting electronic properties. Some parameters such as dipole moment, average polarizability and first order hyperpolarizability have been calculated. In order to compare the results of molecules and with those of Urea, we have computed first molecular hyperpolarizability ꞵ, doped structures (ET chlorinated and brominated) find applications in telecommunication, in modern communication technology and data storage as NLO active materials. Moreover, the chemical potential, ionization potential, electron affinity, electronegativity, global hardness, softness, refractive index, dielectric constant, electric field and electric susceptibility have also been determined. The results show that there is a good electronic transfer within the doped molecules and could have potential applications as semiconductor components, photovoltaic and photonic devices. Finally thermodynamic properties have been also computed.