Distributed feedback lasing in thermally imprinted phase-stabilized CsPbI${}_3$ thin films

All-inorganic cesium lead halide perovskites (CsPbX${}_3$, with X = I, Br, Cl) are of great interest for light-emitting diodes and lasers, as they promise improved thermal stability compared to their organic-inorganic analogues. However, among this family of materials, CsPbI${}_3$ shows a detrimental phase instability that causes the perovskite to convert to a thermodynamically preferred non-perovskite phase (yellow phase) at room temperature. In fact, reports on lasers using thin films of CsPbI${}_3$ as gain medium are missing, as of yet. Here, the first distributed feedback (DFB) lasers based on CsPbI${}_3$ thin films are presented with a resonator directly patterned into the perovskite by thermal nanoimprint. This breakthrough is unlocked by the additive polyvinyl pyrrolidone (PVP), that affords the formation of perovskite layers consisting of phase stable γ-CsPbI${}_3$ nanocrystals, that are even preserved during thermal imprint at 170 °C. The DFB lasers show a low lasing threshold of 45 µJ cm${}^{-2}$ at room temperature under optical pumping and a tunable emission in the deep red spectral region between 714.1 to 723.4 nm. It is anticipated that the findings of this work will have a broad relevance for future electrically driven perovskite lasers and for light-emitting diodes based on CsPbI${}_3$ as active medium. (© 2024 The Author(s). Advanced Functional Materials published by Wiley‐VCH GmbH)