Boosting the Performance of Epitaxial Perovskite Microstructures by Surface Passivation

Epitaxial growth enables the fabrication of films and heterostructures with exceptional properties, particularly when performed on single-crystalline substrates with a suitable lattice type and lattice parameters. While epitaxial growth is extensively utilized for conventional semiconductors, epitaxial micro- and nanostructures of lead-halide perovskites have also been successfully obtained through vapor-phase and liquid-phase deposition techniques. Surface passivation, widely employed in polycrystalline perovskite films and single crystals to suppress surface recombination of charge carriers, is often overlooked for epitaxial structures due to the presumption that their inherently smooth surfaces are free of defects. In this study, surface passivation agents commonly used in colloidal nanocrystal chemistry are investigated, such as trioctylphosphine oxide (TOPO), or protective matrices like poly (methyl methacrylate) (PMMA), to improve the performance of epitaxially grown Formamidinium lead bromide (FAPbBr₃) and Cesium lead bromide (CsPbBr₃) micro- and nanostructures. These findings reveal that surface passivation significantly boosts luminescence intensity and decay times, reduces lasing thresholds to record-low levels for microcrystalline perovskite lasers, and enhances the specific detectivity of photoconductors. These advancements are consistent across structures grown by both vapor deposition and solution processing. This study highlights the critical role of surface passivation for achieving the full potential of epitaxially grown perovskite structures, thereby paving the way for advanced optoelectronic applications.