Atomic-scale characterization of the CdS/CuInSe2 interface in thin-film solar cells

Elemental mixing at the CdS/CuInSe2 interface of a thin-film solar cell was studied by means of atom probe tomography. A Cu-depleted and Cd-doped region (∼2 nm in width) was detected at the CuInSe2 surface, proving the existence of a buried p-n homojunction within the CuInSe2 absorber layer. Furthermore, CdS was found to infiltrate open pores existing in CuInSe2 during the chemical bath deposition. This could explain why chemical bath deposition of CdS leads to higher solar cell efficiencies compared to physical vapor deposition of CdS.