Amoroso, Davide (2024) Investigation and modelling of tin-based perovskites production process from colloidal suspensions to thin films for photovoltaic applications. [Tesi di dottorato]

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Abstract

Tin-based perovskite materials have emerged as promising candidates for lead-free solar cells due to their cost-effectiveness and reduced toxicity. Nonetheless, these materials exhibit a notably higher crystallization rate compared to lead-based counterparts, often leading to non-homogeneous film morphology and increased electron trap density. Given the inefficiencies associated with trial-and- error optimization methods, it is advantageous to model the perovskite production process, which is the primary objective of this thesis. The first approach is modelling the spin-coating process with the lubrication-theory-based approximated form of the Navier-Stokes equations and comparing the results with the time evolution of the liquid film thickness during rotation. The simulation data are in good agreement with the experimental results, but we are unable to obtain information about the microstructure of the material. Recent research trends suggest that perovskite solutions should be perceived as colloidal suspensions rather than conventional chemical solutions. Consequently, there is a growing interest in harnessing colloidal properties to influence the kinetics of perovskite formation. This thesis employs a combination of colloidal suspension characterization techniques, including Dynamic Light Scattering (DLS), alongside in situ characterization methods such as Grazing-Incidence Wide-Angle X-ray Scattering (GIWAXS), Photoluminescence (PL), and UV-Vis spectroscopy to analyze the perovskite formation process. Specifically, we performed a comprehensive comparative analysis, juxtaposing the additive-free suspension with ones containing various additives (tin chloride, ethane-1,2-diammoniumiodide, 4-tert-butylpyridine) to gain deeper insights into the effects of these additives on crystallization dynamics. Finally, we have also investigated the use of gas quenching as an alternative to anti-solvent treatments in the manufacture of tin-based perovskite solar cells. This approach allows controlled crystallization of the perovskite films without the need for anti-solvents, offering a potentially more efficient and scalable method for device fabrication.

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