Optimal composition of earth abundant CZTS precursors for photovoltaics application

Kesterite Cu2ZnSnS4 (CZTS) based solar cell recently become more popular due to its elemental abundance and similarity to CIGS solar cells. However, the power conversion efficiency produced by CZTS is still lower than CIGS. Thus, the investigation of the optimum composition of various precursor materials used in CZTS solar cells and the effect of Zn/Sn ratio to the efficiency of the solar cells was conducted to further study the absorber layer of this solar cell. CZTS solar cell were successfully fabricated on Molybdenum-coated glass by spin coating technique with variation of precursors such as zinc chloride, zinc acetate, and zinc nitrates for the Zn precursors and copper acetate and copper chloride for the Cu precursors, while for the tin and Sulphur precursors, the tin chloride and thiourea were used respectively. This was followed by annealing through sulphurization and selenization process. X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) were performed to investigate the crystal structure and morphology of the solution coated on the substrates. The result shows that the highest efficiency obtained by using zinc chloride and copper acetate for the Zn and Cu precursor respectively are 3.2 % and 4.1 % for annealing method through sulphurization and selenization respectively. These results are also supported by the grains that were found out to be larger and more crystalline than the others. Besides that, it was found that the efficiency decreases as more zinc nitrate incorporated as the Zn precursor. Once the optimum composition of the solar cells was obtained, the ratio of Zn/Sn were tuned to investigate the effect to the solar cell efficiency. Having undergone the same fabrication method as previously done, the highest efficiency obtained in the solution with ratio of Zn/Sn = 1.4 for both methods of annealing, with the efficiency of 2.9 % and 3.0 % through sulphurization and selenization respectively. This is due to the Zn-rich layer is promoted as the ratio increases. The larger grains were also observed with increasing ratio of Zn/Sn.Bachelor of Engineering (Materials Engineering