Impact of composition, shape, and environment on the physical and optoelectronic properties of cesium lead halide perovskite nanocrystals

Abstract

Perovskite nanocrystals have electronic and optical properties that could be advantageous in electronic devices. This dissertation aims to understand how post synthetic processing impacts the electron dynamics of CsPbBr3 nanocrystals using spectroscopy techniques to provide fundamental information on the properties of perovskites. To investigate how the tunability of CsPbX3 nanocrystals affects the electron dynamics, we synthesized CsPbBr3 nanocubes via a hot-injection process. Then, we performed anion exchange reactions to vary the ratio of chlorine to bromine in the nanocrystals. We also compared the electron dynamics as a function of morphology for bulk CsPbBr3, and CsPbBr3 nanocubes and nanowires. Finally, we observed how the environment surrounding the nanocrystals impacts their optical properties by varying the solvent to dictate self-assembly and using uv-vis and photoluminescence spectroscopies to see how their optical properties change. As the ratio of Cl to Br increased in CsPb(Br1-xClx)3, the photoluminescence quantum yield decreased, the rate of carrier cooling increased, and the magnitude of the hot-phonon bottleneck effect decreased. As we varied the morphology of CsPbBr3 from bulk to nanocubes to nanowires, radiative recombination became more rapid and the hot-phonon bottleneck effect was more pronounced in the nanostructures. Finally, varying the polarity of the solvent used to wash CsPbBr3 nanocrystals allowed us to control the formation of 1D superlattices via the tuning of van der Waals forces, and hydrophobic interactions involved in solvent-ligand interactions. These findings provide fundamental insights that can be generalized to other perovskite structures and provide strategies for incorporating perovskites into optoelectronic devices.