Directional and Collimated Photoluminescence From 2D Perovskite Microcrystals via Post-Synthetic Metalens Integration

For emerging frontiers for compact and miniaturized light sources, achieving deterministic control over the spatial wavefront and angular distribution of the emitted photons is paramount. Perovskite microcrystals are promising light-emitting materials, but their intrinsic photoluminescence is typically highly divergent, which hinders efficient light collection and directional control. Here, we demonstrate wavefront engineering of spontaneous emission from a single phenethylammonium lead iodide (PEPI) microcrystal by integrating it with a dielectric metalens. The metalens, specifically designed for the peak emission wavelength, was fabricated on a quartz substrate via two-photon polymerization. Subsequently, an individual PEPI microcrystal was positioned on the opposing quartz surface via a dry-transfer method. This heterostructure effectively reshapes the divergent emission into a highly directional, quasi-collimated beam, reducing the beam-expansion slope from 0.16 to 0.04, corresponding to an approximately fourfold suppression of divergence. Angle-resolved photoluminescence measurements further confirm a significantly narrowed angular distribution of ∼5°following metalens modulation. These results provide a straightforward, non-invasive strategy to tailor the intrinsic emission of individual perovskite microcrystals, establishing a versatile platform for hybrid perovskite–metasurface photonics with enhanced directional emission and collection efficiency.