Ring Patterned Perovskite Single Crystals Fabricated by the Combination of Rigid and Flexible Templates

Regular microstructures can improve the electrical and optical characteristics of perovskite single crystals due to its removal of defects and grain boundaries. Microstructured single crystals are commonly fabricated by either rigid or flexible templates. However, rigid templates usually need surface treatment before crystal fabrication to create an anti-adhesion layer while flexible templates encounter difficulties in achieving large area of uniform single crystals without any deformation. In this work, we present a facile and robust method to fabricate perovskite single crystals using rigid silicon pillars coated with flexible polymer solution, in which the surface treatment is avoided in the preparation process, and the deformation is absent in the formed crystals. The method realized the fabrication of colorful concentric ring pattern composed of nanoscale single crystals for the first time. In order to concisely control the preparation of the template, Newton's ring phenomenon was used to value the droplets height because the number of rings changed with optical path difference. A related digital simulation was performed to find the correlation of Newton's ring pattern with the shape of the droplets. The simulated results are consistent with the experimental observations generally, indicating that the pattern could be controlled mechanically. Concomitantly, the resulting perovskite nanoscale single crystals formed a regular colorful concentric ring pattern. By changing the design of the rigid templates, the parameters of the fabrication process or the selection of the coating polymer solution, different ring patterned single crystals were successfully prepared without surface treatment and deformation. The crystals have potential application in lasers or photodetectors.