Speckle-Free Imaging Based on a Quasi-2D Perovskite Random Laser with a Subwavelength Thickness

Quasi-two-dimensional (quasi-2D) perovskite materials possess remarkable optical properties, including a large exciton binding energy, enhanced stability, and natural quantum-well structures, which have great potential for lasing applications. However, solution-processed quasi-2D perovskite films encounter challenges such as serious defect states, poor crystal quality, and random phase distribution, thereby hindering the practical application of quasi-2D perovskite lasers. Here, we demonstrate random lasers based on quasi-2D (PEA)2MA3Pb4Br13 films with preeminent optical gain by introducing adipic acid (AA) as an additive and further explore their speckle-free imaging. By the introduction of AA, the quality of quasi-2D perovskite films is significantly improved, including suppressed defect states, improved crystalline quality, larger grain sizes, a more homogeneous phase distribution, and enhanced photoluminescence (PL) because of the lowering of the crystallization rate. Moreover, the AA-assisted quasi-2D perovskite film exhibits significantly decreased amplified spontaneous emission (ASE) thresholds from 55.4 to 7.8 μJ/cm2, along with an increased gain coefficient from 332 to 1404 cm–1, which is four times that of the pristine one. Accordingly, the threshold of random lasers based on AA-assisted quasi-2D perovskite films can be reduced to 20% of that of pristine films. Benefiting from the high brightness, narrow bandwidth, and relatively low spatial coherence of the random laser, we realized higher speckle-free imaging of quasi-2D perovskite subwavelength random lasers. This work presents an effective strategy for enhancing quasi-2D perovskites as gain media and expanding their practical applications in optoelectronic devices, particularly in semiconductor lasers.