Cu2ZnSnS4 thin-film solar cell absorber composition revealed by energy-dispersive and soft x-ray emission spectroscopy

Different Cu
₂
ZnSnS
₄
(CTZS) thin-film solar cell absorbers have been investigated by bulk-sensitive energy-dispersive spectroscopy (EDS) and surface-near bulk-sensitive soft x-ray emission spectroscopy (XES). While we find a good agreement between the computed Zn/Sn composition ratio based on the EDS and XES data, the XES determined Cu/(Zn+Sn) composition ratio significantly deviates from that based on EDS measurements for some samples. While the first can be explained by a homogenous Zn/Sn composition throughout the CTZS samples, the latter is interpreted as a variation of the Cu depth profile in the respective thin-film solar cell absorbers.