Programmable Single‐Crystalline PbI₂ Microplate Arrays and Their Organic/Inorganic Heterojunctions

Abstract Deterministic patterning of inorganic semiconducting micro‐/nanostructures has laid the foundation for the on‐chip integration of optoelectronic devices. However, it requires complicated equipment for thin‐film deposition, lithography, and etching. Solution‐processing bottom‐up integration of micro‐/nanostructures has been extensively studied in organic semiconductors and nanoparticles, but solution‐patternable inorganic single‐crystalline micro‐/nanostructures are still elusive. It is still challenging to control the crystallization of inorganic semiconductors in solution processes. Herein, an efficient strategy is developed to steer the crystallization of PbI₂ hexagonal microplates in capillary bridges. Evenly distributed mass and ordered microfluid in each capillary bridge are able to attain simultaneous manipulation of position, size, and crystallographic orientation. Complex patterns, including Latin characters, Arabic numeral characters, and mathematical symbols, are realized by positioning capillary bridges. Based on these high‐quality PbI₂ microcrystals, high‐performance photodetectors are demonstrated with a responsivity of 625 mA W⁻¹, an on–off ratio of 10⁵ and response speeds of τ_rise = 0.31 ms and τ_decay = 0.17 ms. This technique also allows for the integration of PbI₂ microstructures with organic semiconductors to manufacture heterojunction arrays with efficient charge transfer. The strategy provides a perception to fabricate inorganic single‐crystalline microarrays and heterostructures for integrated optoelectronics.