Lasing in all-inorganic halide perovskite semiconductors^*

All-inorganic halide perovskite semiconductors will be presented as gain media for perovskite lasers. Specifically, we will address CsMX 3 , where M=Pb or Sn and X=I, Br, Cl. While in CsPbBr 3 , the control of polymorphs with different dimensionality is important, in CsPbI 3 the preferential formation of the optically inactive $\delta-$phase needs to be prevented. For CsSnBr3, the detrimental oxidation of S$\mathrm{n}^{2+}$ to S$\mathrm{n}^{4+}$ must be suppressed. In case of the CsPbC$1_{3}$, the poor concomitant solubility of the precursor salts prevents solution processing. We show that thermally evaporated superlattices of PbC$1_{2}$ and CsC1 afford the spontaneous formation of CsPbC$1_{3}$ and yield high-quality gain media. The set of active media shown in this work allows tunability of the emission from 410 nm to 720 nm.