Aqueous Solution Printed Low‐Threshold Two‐Photon Pumped Flexible Quasi‐2D Perovskite Amplified Spontaneous Emission Arrays

ABSTRACT Perovskite‐based micro/nano laser arrays, owing to their outstanding optical properties, are highly promising candidates for chip‐scale light sources. Inkjet printing, known for its low cost, high efficiency, and tailor‐made designs, offers an attractive pathway to create perovskite laser arrays. However, existing perovskite inkjet printing heavily relies on toxic solvents (like DMF/DMSO), compromising its environmental friendliness and large‐scale adoption. To address this challenge, we unveil a novel method for fabricating quasi‐2D Ruddlesden‐Popper (RP) perovskite laser arrays via aqueous solution printing. By controlling crystallization kinetics and minimizing interface defects during the in situ growth of RP‐type perovskites from water, custom‐made RP‐type perovskite arrays achieve exceptional optical characteristics. The resulting arrays exhibit mode‐stable amplified spontaneous emission (ASE) under two‐photon pumping, activating at an ultra‐low threshold of 25 µJ/cm 2 . Furthermore, by integrating onto a flexible substrate, we successfully fabricated a bendable perovskite ASE array capable of exhibiting stable ASE in both flat and curved configurations. In contrast to traditional techniques, our aqueous solution‐based printing approach enables the environmentally compatible production of perovskite laser arrays. This method eliminates the need for toxic solvents and imparts the devices with high flexibility. This work demonstrates the potential for fabricating flexible, budget‐friendly, and eco‐conscious perovskite optoelectronic devices.