Facet-controlled preparation of hybrid perovskite microcrystals in the gas phase and the remarkable effect on optoelectronic properties

Within only a few years, hybrid perovskites have become one of the most intriguing semiconductors in different light-harvesting and light-emitting applications. Their optimization for targeting technological implementation can only be achieved if one gathers knowledge of their fundamental material properties and how they are influenced by factors like composition, particle size, and shape. Not only is shaping hybrid perovskite particles difficult, but capping agents binding to crystal surfaces might influence the intrinsic properties as well. We present a new aerosol-assisted crystallization with a liquid single-source precursor for making shaped CH3NH3PbBr3 crystals with naked facets. The formation of microcrystals with either predominant (001) facets or the less favorable (011) facets is achieved. We were able to assemble the particles in a defined orientation on a substrate to investigate the facet influence on the optical properties. We find not only a pronounced influence on the lifetime of the photo-generated charge carriers, but also a shift in the photoluminescence energy, and, using confocal fluorescence spectroscopy, a facet-dependent local enhancement of the fluorescence features. Our study demonstrates that the particle shape is an important tool to modify the properties of hybrid perovskites for optoelectronic applications.