Compensation-doped silicon for photovoltaic applications

A small overlap between the silicon optical absorption spectrum and the solar spectral irradiance limits the conversion efficiency of crystalline thin-film silicon solar cells. In this work, a theoretical search for compensation-doped silicon is carried out aiming to maximize the spectral overlap. First, a wide range of dopant species and concentrations is considered using the virtual crystal approximation and the empirical pseudopotential method. Second, the most promising modifications of silicon are investigated using the supercell method and a first-principles many-electron Green's function approach. In both steps, the optical absorption spectrum is computed by solving the Bethe-Salpeter equation to include excitonic effects. It is found that the conversion efficiency of a silicon film of 10 mu m thickness can be increased by 25% by a 1.6 at. % compensation doping with In and Sb.