title: Quantitative Phase-Change Thermodynamics and Metastability of Perovskite-Phase Cesium Lead Iodide.
abstract: The perovskite phase of cesium lead iodide (α-CsPbI3or "black" phase) possesses favorable optoelectronic properties for photovoltaic applications. However, the stable phase at room temperature is a nonfunctional "yellow" phase (δ-CsPbI3). Black-phase polycrystalline thin films are synthesized above 330 °C and rapidly quenched to room temperature, retaining their phase in a metastable state. Using differential scanning calorimetry, it is shown herein that the metastable state is maintained in the absence of moisture, up to a temperature of 100 °C, and a reversible phase-change enthalpy of 14.2 (±0.5) kJ/mol is observed. The presence of atmospheric moisture hastens the black-to-yellow conversion kinetics without significantly changing the enthalpy of the transition, indicating a catalytic effect, rather than a change in equilibrium due to water adduct formation. These results delineate the conditions for trapping the desired phase and highlight the significant magnitude of the entropic stabilization of this phase.
authors.affiliation: Department of Chemical and Biological Engineering, Drexel University , 3141 Chestnut Street, Philadelphia, Pennsylvania 19104, United States.
authors.forename: Subham
authors.identifier: http://orcid.org/0000-0002-3025-4787
authors.initials: S
authors.lastname: Dastidar
authors.affiliation: Department of Materials Science & Engineering, Drexel University , Philadelphia, Pennsylvania 19104, United States.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Hawley
authors.affiliation: Department of Chemical and Biological Engineering, Drexel University , 3141 Chestnut Street, Philadelphia, Pennsylvania 19104, United States.
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Dillon
authors.affiliation: Department of Materials Science & Engineering, Drexel University , Philadelphia, Pennsylvania 19104, United States.
authors.forename: Alejandro D
authors.initials: AD
authors.lastname: Gutierrez-Perez
authors.affiliation: Department of Materials Science & Engineering, Drexel University , Philadelphia, Pennsylvania 19104, United States.
authors.forename: Jonathan E
authors.initials: JE
authors.lastname: Spanier
authors.affiliation: Department of Chemical and Biological Engineering, Drexel University , 3141 Chestnut Street, Philadelphia, Pennsylvania 19104, United States.
authors.forename: Aaron T
authors.initials: AT
authors.lastname: Fafarman