The structural and electronic properties of Cu(In1−xBx)Se2 as a new photovoltaic material

Abstract

The newly synthesized solar cell absorber material Cu(In_1−xB_x)Se₂ based on a solvothermal method with a special solvent is investigated using density functional theory. Our results show that Cu(In_1−xB_x)Se₂ has an extremely high formation enthalpy which indicates that it is hard to synthesize using a traditional evaporation method. The band gap of Cu(In_1−xB_x)Se₂ increases with increasing B content with a larger bowing parameter than that of Cu(In_1−xGa_x)Se₂. The band alignment of CuInSe₂ and CuBSe₂ is of type II. And the upshift of the valence band maximum is much smaller than that of the conduction band maximum for CuBSe₂, which indicates that pure CuBSe₂ can easily be p-type doped but that n-type doping could be more difficult in the alloy with a high B content. Therefore, we expect that the high efficiency Cu(In_1−xGa_x)Se₂ solar cell material has a low B content.