Distributed Feedback Lasers Based on Phase-Stabilized CsPbI₃ Thin Films

All-inorganic cesium lead halide perovskites (CsPbX₃, X = I, Br, Cl) are gaining significant attention for their use in light-emitting diodes and lasers, owing to their enhanced thermal stability compared to organic-inorganic hybrid perovskites. While CsPbBr₃ has been extensively studied for stimulated emission and lasing^[1], CsPbI₃ has not received the same level of attention despite its favorable optical properties, with a band gap of about 1.7 eV and emission in the red spectral region. The phase instability of CsPbI₃ causes it to assume a non-perovskite phase (yellow phase) at room temperature, which limits its practical application in devices.
In this presentation, we introduce the first distributed feedback (DFB) lasers utilizing CsPbI₃ thin films, featuring a resonator directly patterned into the perovskite. The additive polyvinylpyrrolidone (PVP) is employed to stabilize the CsPbI₃ thin film in the black phase at room temperature. Previously, we could show that various halide perovskites can be patterned by thermal nanoimprint ^[2,3]. Here, we use thermal nanoimprint to pattern second order DFB gratings directly into the perovskite active layer. The γ-CsPbI₃ phase stabilized by PVP remained stable during thermal nanoimprinting at temperatures up to 170°C. Our DFB lasers demonstrate a low lasing threshold of 45 μJ cm^-2 at room temperature under picosecond pulse laser excitation, with tunable emission in the deep red spectral range from 714.1 nm to 723.4 nm^[4]_. Additionally, as a further laser application of our phase-stabilized CsPbI₃ thin films, vertical cavity surface emitting lasers (VCSELs) fabricated utilizing the versatility of thermal nanoimprinting in laser device fabrication and their laser characteristics will be presented.
We expect that our results will have significant implications for the development of future electrically driven perovskite lasers and light-emitting diodes (LEDs) that use CsPbI₃ as the active medium.

[1] N. Pourdavoud et. al., Adv. Mater. 2019, 31, 1903717
[2] N. Pourdavoud et. al,. Adv. Mater. 2017, 29, 1605003
[3] N. Pourdavoud et. al,. Adv. Mater. Technol. 2018, 3, 1700253
[4] N. Kurahashi et. al, Adv. Funct. Mater. 2024, 2405976