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

Abstract

Elemental mixing at the $\text{CdS}/{\text{CuInSe}}_2$ interface of a thin-film solar cell was studied by means of atom probe tomography. A Cu-depleted and Cd-doped region ($\sim 2\text{nm}$ in width) was detected at the ${\text{CuInSe}}_2$ surface, proving the existence of a buried p-n homojunction within the ${\text{CuInSe}}_2$ absorber layer. Furthermore, CdS was found to infiltrate open pores existing in ${\text{CuInSe}}_2$ 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.