The properties of fluorine-doped graphene-based intermediate band solar cell materials

Abstract

The impact of carbon atom concentration to the band structure of intermediate band material which made of one fluorine atom doped graphene are researched by first-principles calculations. After geometry optimization, the fluorine atom protruded from the graphene plane gone through a deformation of Jahn-Teller. The formation energies are small indicate that the configurations are stable. By calculating the band structures of four doping models, we found that the 4 × 4 × 1 graphene supercell doped with one fluorine atom which carbon concentration is 3.125 % has more ideal intermediate-band structure. As can be seen from the optical absorption spectrum, there are three distinct absorption peaks appear from the complex. The two sub-band gap absorption on the left are attributed to the combined effect of the electron transition from the top of the valence band to the intermediate band and from the intermediate band to the bottom of the conduction band, while the large absorption peak on the right is due to the electron transition from the bottom of the conduction band to the top of the valence band. The reason for this phenomenon should be that the polarity of C-F bonds is much larger than that between C-C bonds, and the doping of fluorine atoms causes the charge transfer between atoms, resulting in the opening of the graphene band gap and the introduction of the intermediate band.