Systematic study of effects of solvents on structural and optical properties of CsPbBr₃ nanocrystals

Razdan, Samarth (2022) Systematic study of effects of solvents on structural and optical properties of CsPbBr₃ nanocrystals. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS dissertation of Samarth Razdan (17MS121)) 17MS121_Thesis_file.pdf - Submitted Version Restricted to Repository staff only Download (2MB)

Abstract

Lead halide perovskites have emerged as an attractive material for optoelectronic applications. This is due to their unique properties, which include, high absorption coefficient, high charge carrier mobility, long diffusion lifetimes, intense photoluminescence properties and high photoluminescence quantum yields. Due to its widespread acceptance in optoelectronic applications, it has become increasingly important to study its fundamental properties. In this work, the effect of solvents of different polarities on the structural and optical properties of CsPbBr₃ nanocrystals was investigated. The structural properties were studied via powder X-ray diffraction technique. From the peak positions and crystallite size calculations, it is evident that the solvent had no effect on the crystal structure and crystallite size. No new phases were formed and no degradation was observed. The optical properties were studied via UV-visible absorption spectroscopy, photoluminescence spectroscopy and time resolved photoluminescence spectroscopy. In the UV-visible measurements, it was observed that the absorption onset showed no dependence on the solvent polarity. Band gaps were calculated using Tauc plots for each solvent, and no dependence could be ascertained here either. Through photoluminescence spectra measurements, it was observed that the PL emission peak underwent a redshift with increase in solvent polarity, which may be explained via solvent relaxation effect. Through time resolved photoluminescence measurements, it was observed that the PL decay lifetime lowered in magnitude with increase in solvent polarity. This can be explained by the interaction between solvent molecules and the capping ligands of the nanocrystal. Hence, an effect of solvent polarity was observed in optical properties of CsPbBr₃ nanocrystals.

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