Effect of 2D MXene-to-nanoparticle ratio on the electronic structure of Ti(3)C(2) MXene-CsPbBr(3) nanocomposites.

MXene-CsPbBr nanocomposites have garnered significant interest for next-generation optoelectronics, combining tunable quantum effects with exceptional charge transport characteristics. Realizing optimal functionality, however, necessitates precise control over the 2D MXene-to-nanoparticle ratio. Herein, we systematically elucidate how this ratio governs the electronic structure and charge dynamics in TiC MXene-CsPbBr nanocomposites using scanning tunnelling spectroscopy (STS), electrostatic force microscopy (EFM), and Kelvin probe force microscopy (KPFM). STS reveals distinct density of states for isolated CsPbBr nanoparticles chemically bonded to MXene compared to aggregated counterparts. Schottky junctions at well-defined interfaces promote charge separation, whereas nanoparticle aggregation induces defect-mediated states, narrowing the CsPbBr bandgap and opening a gap in TiC. Correlated EFM-KPFM analyses further demonstrate that isolated nanoparticles yield uniform electrostatics and homogeneous surface potentials, while aggregates generate localized fields and patchy work-function distributions. These results demonstrate that nanoscale electrostatics and interfacial coupling critically dictate carrier dynamics, enabling the rational design of tunable optoelectronic device architectures.