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Thesis
Understanding and breaking normal grain growth limits in uniaxially compressed perovskite alloys
Master of Science (M.S.), Drexel University
Jun 2025
DOI:
https://doi.org/10.17918/00011073
Abstract
A new generation of solar cell materials known as metal-halide perovskites (MHPs) promises both low cost and scalability. However, a critical fabrication challenge is getting the perovskite crystal to form large individual domains. Previous research has shown that perovskite domains can consolidate laterally during simultaneous heating and uniaxial compression at 100 bar and 150 °C. To date, these studies have been limited to pure component perovskites whereas the compositions optimized for high efficiency and stability are complex alloys. By analogy to the strengthening of metals by alloying, it would be reasonable to expect qualitatively different mechanical response for alloys compared to single-component materials. Herein, we investigate the morphological and microstructural evolution during hot-pressing of one such optimized composition referred to as (Cs/FA/MA)PbX₃, a septenary alloy. Scanning electron microscopy (SEM) and optical profilometry were used to quantify domain size and film thickness, respectively. As deposited, the (Cs/FA/MA)PbX₃ films have small crystal sizes (0.3 [mu]m), which consolidate into larger domains > 1 [mu]m laterally. Alloys appear to be limited to normal grain growth, as reflected in an aspect ratio of 1, whereas tremendously large aspect ratios have been observed in unalloyed perovskites. However, we show that apparent secondary lateral growth of single-component perovskites is likely due to vertical consolidation of small crystallites on top of large existing crystals. Further, we show how the intentional retention of a minute amount of residual solvent can promote secondary growth of massive lateral domains (> 10 [mu]m) in alloys. X-ray diffraction (XRD) suggests that hot-pressing increases the preferred orientation of the perovskite film in the 110-crystal plane, indicating significant recrystallization in both normal and secondary growth regimes. We report that consolidation/recrystallization processes occur regardless of composition, providing access to the benefits of consolidation for state of the art alloys such as (Cs/FA/MA)PbX₃.
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Details
- Title
- Understanding and breaking normal grain growth limits in uniaxially compressed perovskite alloys
- Creators
- Mya Soukaseum
- Contributors
- Aaron T. Fafarman (Advisor)
- Awarding Institution
- Drexel University
- Degree Awarded
- Master of Science (M.S.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- 76 pages
- Resource Type
- Thesis
- Language
- English
- Academic Unit
- Chemical (and Biological) Engineering [Historical]; College of Engineering (1970-2026); Drexel University
- Other Identifier
- 991022059033104721