Unusual Spectrally Reproducible and High Q-Factor Random Lasing in Polycrystalline Tin Perovskite Films.

An unusual spectrally reproducible near-IR random lasing (RL) with no fluctuation of lasing peak wavelength is disclosed in polycrystalline films of FASnI 3 perovskite, which have been chemically stabilized against Sn 2+ to Sn 4+ oxidation. Remarkably, a quality Q-factor as high as ≈10 4 with an amplified spontaneous emission (ASE) threshold as low as 2 μJ/cm 2 (both at 20 K) are achieved. However, RL is also observed at room temperature with a decrease of Q relative low temperature in just one order. Additionally, the specific conditions in which only narrow RL lines are generated have been also found, while the formation of the ASE contour is strongly suppressed. The observed spectral reproducibility is unprecedented for semiconductor thin film RL systems and cannot be explained by the strong spatial localization of lasing modes. Instead, we suggest that the spectral stability is a result of such a unique property of Sn-based perovskites as a large inhomogeneous broadening of the emitting centers, which is a consequence of an intrinsic structural inhomogeneity of the material. Due to this, lasing can occur simultaneously in modes that are spatially strongly overlapped, as long as the spectral separation between the modes is larger than the homogeneous linewidth of the emitting centers. The discovered mechanism of RL spectral stability in semiconductor materials, possessing inhomogeneous broadening, opens up prospects for their practical use as cheap sources of narrow laser lines. This article is protected by copyright. All rights reserved.