Morphological Engineering of Metal Halide Perovskite Films Using Nanoparticle Integration—Impact on Film Quality and Emission Properties

This study focuses on improving the quality of metal halide perovskite films by correlating their morphological characteristics to the spectral broadening of emission. Dephasing processes cause spectral broadening of emission, and controlling them can lead to longer carrier lifetimes and increased quantum yield, enhancing device efficiencies across a wide range of applications from solar cells and LEDs to quantum technologies. Building on our prior research, where layering of metal halide perovskite quantum dots (PQDs) on methylammonium lead iodide (MAPI) improved stability, passivated defects, and increased charge carrier lifetimes and extraction efficiency, this work incorporates PQDs and perovskite magic-sized clusters (PMSCs) within the MAPI film during crystallization. This approach allows us to alter the morphology of the films. We used X-ray diffraction (XRD) and scanning tunneling microscopy to characterize film structure and morphology. XRD confirmed the tetragonal phase of MAPI, revealing differences in crystallite orientations based on the conducting properties of the nanoparticle ligands. Optical characterization using spatially resolved photoluminescence (PL) showed emission peak shifts in nanoparticle-incorporated films, correlating with nanoparticle sizes. Although it showed uniformity in emission peak energy across individual nanoparticle-incorporated films, this compositional consistency indicates minimal local strains caused by incorporating nanoparticles and reduced inhomogeneous broadening. Time-resolved spectroscopy demonstrated varied charge dynamics with nanoparticle addition, with a two-fold increase in carrier lifetimes observed for PQDs functionalized by conducting ligands. To investigate dephasing mechanisms, we conducted power-dependent PL studies, which revealed the impact of carrier density on dephasing mechanisms. Temperature-dependent PL studies from 20K to room temperature provided insights into exciton-phonon coupling. Analysis of PL linewidth temperature dependence showed changes in coupling strength for nanoparticle-incorporated films. This approach allowed us to understand the effects of nanoparticle integration. Varying the density of nanoparticles can provide additional control in optimizing film properties. Our findings offer crucial insights into the interplay between nanostructure morphology, crystal dynamics, and dephasing mechanisms in perovskite thin films. The integration of carefully selected nanoparticles presents a promising route for controlling dephasing processes, thereby enhancing the optical properties of these materials for advanced applications.