Regensburg 2025 – scientific programme
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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur
KFM 16: Perovskite and Photovoltaics II (joint session HL/KFM)
KFM 16.7: Talk
Thursday, March 20, 2025, 11:15–11:30, H13
Unravelling how solvated PbI2 Crystallites precede the Crystallization of Lead Halide Perovskites by UV/VIS In-Situ measurements — •Maximilian Spies1, Simon Biberger1, Fabian Eller2, Eva M. Herzig2, and Anna Köhler1 — 1Soft Matter Optoelectronics, University of Bayreuth, Bayreuth, Germany — 2Dynamics and Structure Formation, University of Bayreuth, Bayreuth, Germany
The fabrication of reproducible, high-quality lead iodide perovskite films via solution-based methods requires a comprehensive understanding of crystallization dynamics. The formation of perovskite films is primarily dictated by the composition of the precursor solution and its processing conditions. In this study, we present an in-situ absorption study, i.e. during spin-coating, of the critical pre-nucleation stage to unravel the formation mechanisms of lead iodide perovskite films. We tracked the evolution of iodoplumbate complexes within the precursor solution and identified a distinctive absorption feature at 3.15 eV, emerging prior to film formation. We attribute this feature to the development of a crystalline PbI2-DMF solvated (PDS) phase. In particular, we propose that PDS crystallites serve as precursors to the crystalline perovskite phase, acting as nucleation sites within the precursor solution. Notably, the amount of this PDS phase correlates closely with the concentration of the solution layer during spin coating, suggesting that increasing concentration promotes PDS formation. These findings provide valuable insights into the early stages of perovskite crystallization.
Keywords: optical in situ spectroscopy; precursor solution; solution processing; crystallization; sol-gel