Conversion Efficiency of Intermediate Band Solar Cells with GaAs:N $\delta$-Doped Superlattices

The performance of intermediate band solar cells using a GaAs:N $\delta$-doped superlattice (SL) as the optical absorber is analyzed. In GaAs:N $\delta$-doped SLs, both of the $E_{+}$ and $E_{-}$ bands formed around the N $\delta$-doped layers form SL potentials with the conduction band of the spacer GaAs layers, resulting in the formation of multiple minibands. The conversion efficiency limits of the solar cells are calculated using the detailed balance model based on intermediate band structures composed of the valence band and two minibands formed respectively in the $E_{-}$- and $E_{+}$-related SL potentials. A high efficiency of 62.6% for full concentration is expected by properly adjusting the structural parameters of the SL. Alloying other elements such as In to a GaAs:N $\delta$-doped SL is a possible way to further facilitate the development of intermediate band materials for high-efficiency solar cells.