Influence of stacking order and sulfurization parameters on properties of CZTS thin films grown on flexible molybdenum substrates

In this thesis study, Mo-foil/CuSn/Cu/ZnS, Mo-foil/CuSn/ZnS/Cu, and Mofoil/ZnS/CuSn/Cu precursor layer sequences were produced using the magnetic sputtering method on flexible molybdenum (Mo) foil followed by sulfurization process using the Rapid Thermal Annealing (RTP) method to obtain the kesterite CZTS phase, resulting in the production of CZTS-I, CZTS-II, and CZTS-III films respectively. The crystallite sizes and microstrains calculated using the (112)-preferred orientation XRD peak Full Width at Half Maximum (FWHM) values showed that the CZTS-III sample had a more promising crystalline quality. Raman spectroscopy measurements confirmed the formation of the kesterite CZTS phase in all samples and the presence of a small amount of CTS phase. In SEM images of the of Mo-foil/ZnS/CuSn/Cu layer sequence and CZTS-III films, a more distinct, homogeneous, and compact surface morphology was observed. The optical bandgap values of the CZTS thin film samples varied in the range of 1.44–1.50 eV. Photoluminescence (PL) measurements revealed transitions from the conduction band to defect levels rather than band-to-band transitions. Electrical measurements indicated that CZTS-II and CZTS-III films had lower resistivity and higher carrier concentration due to their better crystalline quality.