Bandgap Tuning on Cu2ZnSn(SxSe1-x)4 absorbers using electron beam evaporated precursor stack

Copper Zinc Tin Sulfo-Selenide (Cu
₂
ZnSn(S
_x
Se
_1-x
)
₄
) (CZTSSe) with varying S and Se composition has gained research interest owing to its tunable bandgap, high absorption coefficient value and relatively high earth abundance. In this study, CZTSSe films are prepared using electron beam evaporated glass/Mo/Sn/Zn/Cu precursor stacking sequence and then sulfo-selenized in presence of mixture of elemental S and Se powders in different ratios at 500 °C at low ramping rate (1 °C/min). Formation of CZTSSe films with an entire range of S/Se ratio is confirmed through X-ray diffraction and Raman spectroscopy. A significant degradation in the morphology with increasing Se content is observed through Field Emission Scanning Electron Microscopy (FESEM) and the composition of the films are estimated using Energy dispersive X-Ray spectroscopy (EDS). The bandgap of the films are found to be decreasing from 1.45 eV to 0.98 eV as the Se content is increased.