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Kinetically Stable Single Crystals of Perovskite-Phase CsPbI3
journal contribution
posted on 2019-07-08, 00:00 authored by Daniel
B. Straus, Shu Guo, Robert J. CavaWe use a solid-state method
to synthesize single crystals
of perovskite-phase cesium lead iodide (γ-CsPbI3)
that are kinetically stable at room temperature. Single crystal X-ray
diffraction characterization shows the compound is orthorhombic with
the GdFeO3 structure at room temperature. Unlike conventional
semiconductors, the optical absorption and joint density-of-states
of bulk γ-CsPbI3 is greatest near the band edge and
decreases beyond the Eg for at least 1.9
eV. Bulk γ-CsPbI3 does not show an excitonic resonance
and has an optical band gap of 1.63(3) eV, ∼90 meV smaller
than has been reported in thin films; these and other differences
indicate that previously measured thin film γ-CsPbI3 shows signatures of quantum confinement. By flowing gases in situ during powder X-ray diffraction measurements, we
confirm that γ-CsPbI3 is stable to oxygen but rapidly
and catalytically converts to non-perovskite δ-CsPbI3 in the presence of moisture. Our results provide vital parameters
for theoretical and experimental investigations into perovskite-phase
CsPbI3 that will the guide the design and synthesis of
atmospherically stable inorganic halide perovskites.