Effects of strain on optical properties of BiFeO3: A first-principles study

In order to investigate the effects of strain on optical properties of BiFeO3, electronic structure, dielectric properties and optical properties of BiFeO3under different strain conditions were performed by first-principles calculations. Results show that the optical spectra of BiFeO3 is mainly determined by the contributions from transition from valence band O 2p to conduction band Fe 3d levels or even higher conduction band Bi 6s states in the low-energy region. Compared with equilibrium state, state density peaks shift to left side and state density peaks become broader and lower, and band gap becomes smaller under strain states. Furthermore, strain increases optical absorption coefficient peaks, energy loss coefficient peaks and reflectivity coefficient peaks, and extinction coefficient peaks, exhibiting that optical properites of BiFeO3 is improved under strain states. Our research provides theoretical guidance for future optical applications of BiFeO3, especially photovoltaic application. © 2016 Trans Tech Publications, Switzerland.