With a view to obtain high performance multiferroic devices for applications in data storage media and multiple storage memories, we have investigated the multiferroic properties of Bi0.92Tb0.08FeO3 for the first time based on density functional theory calculations. Our results on Bi0.92Tb0.08FeO3 reveal the presence of incommensurate band gaps in the up and down spin channels and thus confirm the existence of bipolar magnetic semiconductor, a rare and promising candidate among spintronic materials. The hybridization between Bi, Tb 6s states and O 2p states gives rise to cation off-centering and distortion and the partial density of states indicates the presence of exchange splitting of Fe 3d states. In addition, we have also obtained a ferrimagnetic arrangement of Fe atoms as a result of destruction of the antiferromagnetic spin structure. Accounting for optical properties, when electric field is perpendicular with respect to the crystallographic c axis (E⊥c) the maximum value of refractive index reached to 3.3 at 3.3 eV (375.7 nm, UV region) and 3.3 at 2.5 eV (496 nm, visible region). This is one of the largest values of refractive index known in the visible region of electromagnetic spectrum and thus Bi0.92Tb0.08FeO3 can become a promising candidate for optical communication devices. Also the dielectric constant reaches maximum to 10.6 at 2.5 eV (496 nm, visible region) for E⊥c and 10.5 at 3.3 eV (375.7 nm, UV region). A high polarization value 82.56 µC/cm2 was calculated for Bi0.92Tb0.08FeO3 and is in good agreement with the known experimental values. © 2017 Elsevier B.V.