Abstract:
Hybrid organic materials are widely investigated due to their exceptional optical properties,
high structural flexibility and low-cost production. X-ray scattering techniques are
non-invasive methods which allow studying crystallization kinetics in situ during thin film
growth, unraveling the processes occurring between the deposited solution (liquid state)
and final film (solid state). In order to achieve high spatial and temporal resolution, the
X-rays at synchrotron facilities have to be used. This requires a special sample environment
with various remotely controlled systems to be installed at the diffractometer.
This work is focused on the development of a compact sample environment for studying
hybrid organic-inorganic materials by in situ grazing incidence X-ray scattering (GIWAXS)
and revealing crystallization kinetics during spin-coating and subsequent annealing. The
spinning motor features speeds from 500 rpm up to 10000 rpm with a low ”wobbling”
amplitude, which ensures the stability of the angle of incidence during the scattering experiments.
The annealing for completing thin film crystallization is done by a halogen
lamp targeted at the sample surface. For monitoring the optical properties of thin films,
differential reflectance spectroscopy (DRS) was adjusted to the spin-coating chamber. The
detailed description of each system designed and introduced into the chamber is provided.
All systems used for sample deposition and characterization are remotely controlled via
TANGO. The chamber was successfully integrated and tested at the Deutsches Elektronen-
Synchrotron (DESY) and European Synchrotron Radiation Facility (ESRF).
For the demonstration of the designed chamber performance, the materials used as active
layers for solar cells, namely organic-inorganic perovskites, were deposited as thin
films using three solution-based methods: one-step deposition, antisolvent-assisted and
gas quenching methods. The crystallization kinetics of various perovskite compositions
from precursor solutions were studied by in situ GIWAXS depending on the cations and
halides. The research of this work highlights the influence of different cations and halides
on the pathways of the three-dimensional (3D) perovskite phase formation. Besides that,
two-dimensional (2D) perovskite compositions with various spacer and small cations were
studied, the interplay of the forming phases and their preferred orientations was analysed
and summarized. In particular, annealing profiles directly affect the orientation of spacer
cations in 2D perovskite phases.
The designed chamber is essentially only a beginning of the journey to reveal the crystallization
complexity of thin films, deposited from solution. The acquired structural
information during real-time experiments can be used for the optimization of the deposition
procedures, tracking the influence of different conditions on the film quality, and
avoiding the unnecessary and detrimental phases.
spin-coating