Characterizing the Solvation Structure of Lead Halide Perovskite Inks

Solvent selection in metal halide perovskite (MHP) precursor inks is essential for controlling thin-film crystallization. Coordination engineering is a widely used approach for optimizing thin-film morphology; however, significant gaps remain in understanding the coordination chemistry of solvated haloplumbate complexes in these inks. While various structures have been proposed, the exact nature of these solvation complexes and a detailed picture of their extended solvation structure remain unclear. In this study, we present a collection of structural motifs found in prototypical MHP chemistries, ranging from mononuclear to polynuclear solute clusters. To classify and differentiate these motifs, we have established a systematic framework that uses a combination of X-ray absorption spectroscopy (XAS), small-angle X-ray scattering (SAXS), and X-ray pair distribution function (xPDF) techniques. The solvation structure of individual complexes and their clustering in solution were modeled using a combination of density functional theory (DFT) and molecular dynamics (MD) simulations. These models were iteratively refined against experimental data through forward scattering simulations, and a comprehensive statistical analysis was performed on the resulting structures. This revised picture of MHP solution chemistry provides crucial insights to guide the strategic development of new MHP chemistries, both 3D and 2D, through informed coordination engineering practices.