Crystal growth and the magic temperature
The basic idea is to form the so called perovskite crystal structure applied as thin layers on (usually) a TiO2/FTO substrate. One requirement to obtain high performances is to have closed layers that homogeneously cover the substrate. However this is not as simple as it sounds since the layer fabrication is very sensitive to many external conditions such as the selection of the precursors, temperature, pressure, humidity, and crystallization rate. Consecutively, a systematic study on the crystal growth resp. the layer formation mechanisms might lead to an important insight and understanding of how to reproducibly prepare high-performing perovskite layers. My day at EMIL was connected exactly to the study of the crystal growth mechanism and the deposition of the precursor thin films. Before we started working, Núria explained me that the layer formation of the precursor SnCl2 is highly temperature-dependent. Consecutively she was really interested to deposit the thin films at different temperature variations between 50 and 150 degrees Celsius. This was part of her Master thesis preparatory work.
Following the deposition, Núria probed the films to check if they had a complete surface coverage. This analysis was carried out with X-ray-based spectroscopy methods. To assess the thickness of the deposited films, scanning electron microscopy images were taken and analyzed. This microscope produces high-resolution images of the surface of the sample. Núria was investigating how parameters like temperature, deposition rate, etc. had to be adjusted for a deposition with a reasonable film thickness.