Optimization of p-Type CZTS Nanocrystal Thin Film Layers For Applications in Low Cost Photovoltaic Devices

In this thesis Cu2ZnSnS4 nanocrystal synthesis was optimized by way of photoelectrochemical measurements through tuning the stoichiometry. Formation of a Cu2ZnSnS4 light-absorbing layer was studied using multiple depositions methods. These included dropcasting, electrophoretic deposition, and use of 3-mercaptopropyl trimethoxysilane as a chemical linker. Dropcasting samples were compared according to the solvents used to suspend the nanocrystals. Photoelectrochemical measurements were used to compare dropcasting with electrophoretic deposition and use of 3-mercaptopropyl trimethoxysilane as a chemical linker. Dropcasting was shown to be the least effective method of depositing the light-absorbing layer. Samples prepared by electrophoretic deposition were optimized according to a number of variables, which included deposition time, nanocrystal concentration, solvent and applied potential. A concentration of 2 g/L, in isopropanol with an applied potential of 50 V for 40 seconds gave the largest photocurrent of all films tested (106 μA/cm2). Using 3-mercaptopropyl trimethoxysilane as a chemical linker photocurrent results as high as 74 μA/cm2 was observed from a much thinner layer. Preliminary solar cells were fabricated using electrophoretic deposition, one of the cells fabricated had a fill factor of 0.27. In this thesis electrophoretic deposition was proven to be the best method of depositing Cu2ZnSnS4 nanocrystals. While a functioning solar cell was fabricated, preliminary cells showed room for much improvement. This shows that upon further optimization, an efficient solar cell can be realized