Researchers at HZB, Humboldt University and Technische Universität Berlin have used small-angle scattering at the PTB X-ray beamline of BESSY II to experimentally investigate the colloidal chemistry of perovskite precursor solutions used for solar cell production. The results could contribute to the optimization of the manufacturing process and quality of perovskite materials.
Until now, the team explains, it has not been possible to achieve a comprehensive impression of the role of the colloidal chemistry in the precursor that is considered to be directional for crystallinity and the further processing. Now, a team led by Prof. Antonio Abate has used small-angle scattering to experimentally determine how the initially disordered elements in the precursor solution find their way into primary subunits, interacting and thus providing a first "pre crystalline" arrangement for further conversion to perovskite thin films.
"While conventional methods have so far limited us to measure only highly diluted precursor solutions, HZB's ASAXS instrument at PTB's FCM beamline at BESSY II makes it possible to study the precursor at a concentration applicable for solar cell fabrication," emphasizes Marion Flatken, who carried out the measurements as part of her PhD thesis.
"Small-angle scattering is ideally suited for measuring nanoparticles and substructures in solutions," explains Dr. Armin Hoell, an expert for small-angle scattering and a corresponding author of the study. "The measured data provide clear evidence for the formation of initial nanometer-sized clusters, which fit the PbI6 octahedron well in terms of dimension and organize themselves in a concentration-dependent manner. Importantly, the measurements are also highly reproducible."
The presented technique and related results can help to further optimize the fabrication process and to more systematically control the quality of perovskite thin films during solar cell fabrication striving for optimal performances.
