Optimization of substrates and physical properties of CdS thin films for perovskite solar cell applications

The physical properties of cadmium sulfide (CdS) thin films have been optimized using different substrates for perovskite solar cell applications as electron-transport layer. The films were deposited by electron beam evaporation on glass, fluorine doped tin oxide (FTO), indium tin oxide and silicon wafer (n-type) and characterized by different respective tools. XRD results show that the films have cubic zinc blende structure with (111) as preferred orientation for all substrates and the calculated crystallographic constants are also discussed. The direct band gap is found 2.41 eV for the films deposited on FTO substrates which is suitable for electron-transport layer in perovskite solar cells due to its good conductivity, crystallinity and an appropriate conduction band level. The electrical studies show that the characteristic behavior is almost linear in both the directions and the conductivity is found to maximum for FTO substrate. The films are also found to be homogeneous, smooth, uniform and free from crystal defects as revealed by SEM studies.