Ternary System CsI–PbI<sub>2</sub>–BiI<sub>3</sub> and Thermodynamic Stability of Cesium Metal Halide Perovskites
Andries van Hattem, D. Alders, R.J.M. Konings, Anna L. Smith
Abstract
High Resolution Image Download MS PowerPoint Slide The thermochemistry of the ternary system CsI–PbI 2 –BiI 3, of interest for applications in photovoltaics, memory devices, and nuclear applications, among other things, is investigated in this work. The binary phase diagrams CsI–PbI 2 and CsI–BiI 3 were subjected to renewed experimental investigation, and the compounds CsPbI 3, Cs 4 PbI 6, and Cs 3 Bi 2 I 9 were found to be the only stable phases in the investigated temperature window. The liquidus lines and invariant equilibria were determined. The phase equilibria in the BiI 3 –PbI 2 system were measured for the first time by using Differential Scanning Calorimetry (DSC). The end-members form a solid solution over the entire composition range. The pseudobinary section CsPbI 3 –Cs 3 Bi 2 I 9 of the CsI–PbI 2 –BiI 3 ternary system was moreover measured by DSC, as well as the ternary eutectic points. A thermodynamic model of the complete CsI–PbI 2 –BiI 3 system was developed by using the Compound Energy Formalism (CEF) for the solid phases and the Modified Quasichemical Model in the Quadruplet Approximation (MQMQA) for the liquid phase. The binary systems were modeled first, and no ternary interaction parameters were found necessary to reproduce accurately the phase equilibria in the ternary system. With our model, the whole liquidus surface of the field CsI–PbI 2 –BiI 3 is described for the first time.