Solution‐Processed Large‐Scale Concentric‐Ring Laser on Two‐Dimensional Ruddlesden–Popper Perovskites Thin Films

Self‐assembly of large‐scale periodic structures is promising for the applications of optoelectronic devices and enhancing light trapping or extraction in optoelectronics. Spontaneous pattern formation provides a facile and large‐area fabrication technology for ordered concentric‐ring patterns. Herein, a facile and robust solution‐processed method for the controllable spontaneous formation of concentric‐ring patterns on 2D Ruddlesden–Popper perovskite (2D‐RPP) thin films is presented. High‐quality (sub)millimeter‐scale concentric multi‐rings are prepared and their parameters can be adjusted by experimental conditions. The obtained 2D‐RPP concentric‐ring patterns show excellent lasing behaviors with high‐quality factor and significantly low lasing threshold. This strategy can be exploited for the development of high‐performance 2D‐RPP laser arrays and the integration of optoelectronic devices. A controllable spontaneous‐pattern‐formation method for the fabrication of concentric‐ring‐pattern lasers on 2D Ruddlesden–Popper perovskite (2D‐RPP) thin films is developed. These submillimeter‐scale regular 2D‐RPP concentric rings present low‐threshold lasing behaviors with very high quality factor, outstanding laser‐mode modulation, and stability.