Theoretical Design of the Absorber for Intermediate Band Solar Cells from Group‐IV (Si, Ge, and Sn)‐Doped AgAlSe2.

Recently, chalcopyrite compounds have been extensively studied as the absorber for solar cells. Inserting an intermediate band in the main band gap of the absorber has been proposed to exceed the Shockley–Queisser limit on single band solar cells. In this paper, the group‐IV elements Si, Ge, and Sn substituting at Al site in AgAlSe2 to form an intermediate band in the main band gap has been studied by first‐principles calculations. The half‐filled intermediate bands from the antibonding state of group‐IV s state and Se‐p state show delocalized characteristics and just shift from each other in Si, Ge, and Sn‐doped AgAlSe2. Based on the analysis on the position of the intermediate band and defect formation energy, Si‐doped AgAlSe2 has been excluded and Ge and Sn‐doped AgAlSe2 have been suggested as promising absorber for the intermediate band solar cell. A heterojunction based on CuAlTe2, AgAlSe2:Sn, and CdS has been proposed as a suitable device for intermediate band solar cells after considering the lattice mismatch and band alignment. [ABSTRACT FROM AUTHOR]