Synthesis and stability of CsSnBr3 perovskite nanocrystals

This thesis presents a modified synthetic method and techniques to enhance the stability of CsSnBr3 perovskite nanocrystals. This modification includes modifying the followed hot injection method and the purification process. As the original hot injection method caused an aggregation problem to the synthesized nanocrystals, both temperature of the injection was changed from 250°C to 190°C and the direction of the injection was redirected from (Cs-Oleate solution to SnBr2 solution) to (from SnBr2 to Cs-Oleate solutions). Additionally, the purification process was also modified by using anhydrous t-butanol to purify the synthesized NCs and by drying N-hexane solvent with molecular sieves before dispersing the NCs in it.  The stability of the nanocrystals was planned to be enhanced. This plan includes choosing four different ligands and investigating the impact of these ligands by measuring both time-dependent absorption and steady-state photoluminescence emission of the treated and the untreated samples. The measurements were conducted under different conditions, which are the inert condition (inside a glovebox filled with Argon with water and oxygen molecules concentrations less than 0.5 ppm) and ambient condition (where the samples were kept in nitrogen-filled sealed flasks, and these flasks were kept outside the glovebox under air). Moreover, the results were presented and discussed in a clear comparison way, explaining the mechanisms leading to such results, where the untreated NCs that was kept under ambient condition show the least the stability and the NCs that were treated with the tetrafluoro benzoic acid ligand show the highest stability under inert condition. However, an additional study was done on the oxidation process of the divalent tin-based perovskite nanocrystals to tetravalent tin-based perovskite nanocrystals, where the impact of the oxygen and water molecules was investigated by monitoring both structural and absorption spectral change of the NCs by measuring their XRD and absorption measurements with time under different environmental conditions and dispersed in different N-hexane status. This further investigation is presented in the appendix.