Spatially Confined Crystallization of Patterned MAPbBr3−xClx Microcrystals

Patterned lead-halide perovskite microstructures are promising for integrated optoelectronics, photonics, and polarization-sensitive devices, but the practical growth behavior of compositionally tunable microcrystals under simple static confinement remains insufficiently understood. Here, we investigate template-assisted confined crystallization of MAPbBr3 and MAPbBr3−xClx microstructures using patterned polydimethylsiloxane (PDMS) stamps. MAPbBr3 was first examined as a reference system to evaluate pattern transfer, morphology, substrate compatibility, and characteristic growth imperfections. Periodic microstructures with template spacings from 0.8 to 10 μm were obtained on Si/SiO2, ITO, PDMS, and MAPbBr3 macrocrystal substrates. Static stamping creates strong edge–center morphological divergence: thick patterned microcrystals and coalesced domains formed preferentially near the sample edges, whereas thinner isolated microcrystal arrays were more common in central regions. XRD, AFM, SEM, SAED, EDX, HRTEM, PL microscopy, and TRPL analyses show that the method can generate well-crystallized and optically active perovskite domains while also producing multidomain aggregates, incomplete pattern transfer, pressure-induced wrinkling, and nanoscale secondary crystallites. Extension to MAPbBr3−xClx demonstrates that patterned mixed-halide microstructures can be obtained with composition-dependent structural and optical properties. Nevertheless, XRD, EDX, PL, and TRPL results indicate that Cl-rich samples are not fully described by a simple homogeneous solid-solution model, likely involving compositionally heterogeneous crystallization and a Br-rich emissive component. Preliminary MAPbCl3-on-MAPbBr3 experiments further show that PDMS-confined patterning can be coupled with substrate-mediated halide exchange or interfacial recrystallization. Overall, static PDMS-confined crystallization is established as a simple exploratory platform for producing diverse patterned perovskite microstructures. This approach is well-suited for the manual selection of suitable crystals and the fabrication of individual microdevices; however, improved control over pressure, mass transport, nucleation localization, and composition will be required when the uniformity of produced patterned microcrystals is desired.