Precursor-Stage Electronic and Stacking-Coherence Modulation of Layered PbI2 via In Situ Ti3C2T x MXene Incorporation.

MXene composite thin films, PbI2-Ti3C2T x , were fabricated by sequential dynamic spin-coating using a water/ethanol precursor system that enables in situ MXene incorporation while avoiding strongly coordinating solvents. This study addresses a central gap in halide precursor engineering: PbI2 is commonly treated as a transient phase before perovskite conversion, although its local structure and electronic environment can influence subsequent material formation. Here, we show that Ti3C2T x incorporation modifies PbI2 at the precursor level without disrupting the 2H-PbI2 framework. Profilometry shows that the average film thickness remains nearly constant across the composition series, whereas roughness and surface morphology evolve with MXene loading. Scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS) identifies Ti-rich clustered regions associated with Pb-I-containing material, supporting a growth-mediated incorporation pathway. X-ray diffraction confirms preservation of the 2H structure, while the PbI2 (001) basal-envelope line shape evolves with composition, consistent with changes in stacking-related environments. Raman spectroscopy shows preservation of the PbI2 vibrational fingerprint together with mode-selective perturbations. X-ray photoelectron spectroscopy (XPS) reveals statistically significant changes in the Pb 4f-I 3d core-level separation, indicating modification of the local Pb-I electrostatic and chemical environment rather than uniform charging or oxidation-state transformation. Optical measurements show a preserved absorption edge, while photoluminescence quenching and photoelectrical response indicate MXene-associated interfacial deactivation and carrier redistribution. Together, these results show that PbI2 can be treated as an engineerable precursor whose local morphology, stacking-related order, and electronic environment can be tuned before conversion into perovskite.