Kinetically Stable Single Crystals of Perovskite-Phase CsPbI₃

Abstract

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-ofstates 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.

Chemically Stable Black Phase CsPbI3 Inorganic Perovskites for High‐Efficiency Photovoltaics

“…Cava and co‐workers first successfully synthesized CsPbI 3 single crystal with a bandgap of only 1.63 eV, which was once considered impossible to synthesize. [ 38 ] They further demonstrated that the bandgap difference between the single crystal and previously reported polycrystal CsPbI 3 is ascribed to quantum confinement effect. The crystal phase of the black phase CsPbI 3 was corrected to orthorhombic phase (γ, Pnam ) from the previously mis‐assigned cubic phase (α, Pm m ).…”

“…Besides the phase stability and PV performance, other physical properties of CsPbI 3 perovskites have also been explored over the years. Cava and co‐workers first synthesized single‐crystal CsPbI 3 perovskite, [ 38 ] as shown in Figure a,b. Despite their thermodynamic instability, bulk single crystals of perovskite‐phase γ‐CsPbI 3 are kinetically stable at room temperature under inert conditions.…”

Low‐Temperature Crystallization of CsPbIBr2 Perovskite for High Performance Solar Cells

“…[ 7–10 ] Inorganic cesium halide perovskites (CsPbX 3 , X = I or Br) without the organic component are attractive in the long run because of their advantages in thermal stability, and chemical resistance. [ 11–13 ]…”

Three New Lead Iodide Chain Compounds, APbI3, Templated by Molecular Cations

“…In particular, lead(II) halide perovskites show impressive performances in their electronic and photophysical properties [5], making them promising candidates for practical applications such as solar cells [6,7] and light-emitting devices (LEDs) [8,9]. α-CsPbI 3 , for instance, exhibits a suitable bandgap (Eg =~1.7 eV), and is an excellent candidate for photovoltaic applications [10][11][12]. The general formula for perovskites is ABX 3 , where A is a large cation, B is a smaller cation, and X is an anion.…”

“…Conversely, not all ABX 3 compositions form perovskites, and several other structural architectures based on linked octahedral BX 6 units are available for such a stoichiometry, incorporating either face-sharing or edge-sharing rather than perovskite-like corner-sharing octahedra [13]. The simple composition CsPbI 3 adopts four different polymorphic forms: α-CsPbI 3 (cubic), β-CsPbI 3 (tetragonal), γ-CsPbI 3 (orthorhombic), and δ-CsPbI 3 (orthorhombic) [10,11,14]. The first three structures are ABX 3 "cubic" type perovskites (α is aristotype cubic, β, and γ can be treated as lower symmetry, distorted structures due to "tilting" of the constituent octahedral PbI 6 units).…”