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Thesis
In situ Study of Methylammonium Lead Iodide Inverse Temperature Crystallization
Master of Science (M.S.), Drexel University
Jun 2021
DOI:
https://doi.org/10.17918/00000419
Abstract
Methylammonium lead iodide (MAPI) has enormous potential for use in next-generation perovskite solar cells, but industrial production is difficult to optimize due to the inherent complexity of uniform and rapid drying of solution based inks. Solutions of MAPI dissolved in gamma-butyrolactone (GBL) display retrograde solubility at high temperatures and offer new possibilities for film fabrication through heating without solvent loss in a process known as inverse temperature crystallization (ITC). Growth of MAPI through ITC, in contrast to evaporative supersaturation, can produce high quality crystals without the typical problems associated with drying such as top-down nucleation. This crystallization mechanism can be applied to scalable manufacturing practices, however to date all studies of ITC have focused on growth of thick films or bulk single crystals or under conditions where ITC and solvent-loss crystallization occur simultaneously. Herein, we have developed a method to deconvolute these two mechanisms by observing MAPI crystallization in situ in rigorously closed and transparent viewing cells prepared by pressing indium metal between glass coverslips that fully prevent solvent loss over the experimental time scale. Study of open samples reveal that under conditions typical of traditional slot-die coating onto a heated substrate, yellow crystalline solids can form and either seed the nucleation and growth of perovskite phase MAPI or undergo an apparent solid-state conversion to the black phase thereby establishing the undersirable yellow morphology in the resulting film. Additionally, study of enclosed samples reveal that MAPI must overcome a high kinetic barrier in order to crystallize via retrograde solubility as indicated by the high degree of supersaturation that is routinely achieved by overheating saturated samples. Finally it is observed that mechanical perturbation of samples in supersaturation conditions can trigger rapid crystallization.
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Details
- Title
- In situ Study of Methylammonium Lead Iodide Inverse Temperature Crystallization
- Creators
- Ryan F. Barrett
- Contributors
- Aaron T. Fafarman (Advisor)
- Awarding Institution
- Drexel University
- Degree Awarded
- Master of Science (M.S.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- ix, 49 pages
- Resource Type
- Thesis
- Language
- English
- Academic Unit
- Materials Science and Engineering; College of Engineering; Drexel University
- Other Identifier
- 991015242080204721