动力学稳定的钙钛矿相CsPbI ${_3}$单晶
Kinetically Stable Single Crystals of Perovskite-Phase CsPbI${_3}$
摘要：
我们采用固相法合成了室温下动力学稳定的钙钛矿相碘化铅铯（$γ$ -CsPbI 3）单晶。X射线单晶衍射分析表明，该化合物为正交晶系，室温下为GdFeO 3结构。与传统的半导体不同，体$γ$ -CsPbI 3的光吸收和联合态密度在带边附近最大，并在Eg之外降低至少1.9 eV。块体$γ$ -CsPbI 3没有显示出激子共振，并且具有1.63（3）eV的光学带隙，比薄膜中报道的小~90 meV;这些和其他差异表明先前测量的薄膜$γ$ -CsPbI 3显示出量子限制的特征。通过在原位粉末X射线衍射测量期间使气体流过$γ$ -CsPbI 3，我们确认$γ$ -CsPbI 3对氧稳定，但在水分存在下快速且催化地转化为非钙钛矿$δ$ -CsPbI 3。我们对体相$γ$ -CsPbI 3的研究结果为钙钛矿相CsPbI 3的理论和实验研究提供了重要的参数，这将指导大气稳定的无机卤化物钙钛矿的设计和合成。
英文摘要：
We use solid-state methods 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 that the compound is orthorhombic with the GdFeO3 structure at room temperature. Unlike conventional semiconductors, the optical absorption and the joint density-of-states of bulk $γ$-CsPbI3 is greatest near the band edge and decreases beyond 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 over $γ$-CsPbI3 during in situ 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 on bulk $γ$-CsPbI3 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.
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