Atomic Scale Structure of (Ag,Cu)2ZnSnSe4 and Cu2Zn(Sn,Ge)Se4 Kesterite Thin Films

Kesterite based materials are being researched and developed as affordable, efficient, mechanically flexible absorber for thin film photovoltaics. Both (Ag,Cu) 2 ZnSnSe 4 Cu Zn(Sn,Ge)Se devices have shown great potential in overcoming some of the remaining challenges further increasing conversion efficiency kesterite solar cells. This study therefore investigates long range crystallographic structure local atomic scale technologically relevant films by means grazing incidence X-ray diffraction low temperature absorption spectroscopy. As expected, unit cell dimensions change about an order magnitude more than element specific average bond lengths. In case , absorbers show a very similar behavior powder samples previously studied. Small amounts residual S were taken into account analysis results imply preferential formation Sn-S bonds instead Ge-S bonds. dependence Ag-Se Cu-Se lengths on Ag/(Ag+Cu) might indicate energetic advantage certain configurations.