Thermodynamics of cesium lead halide (CsPbX3, x= I, Br, Cl) perovskites.

• Thermodynamic stability of CsPbX3 perovskite increases in the order CsPbI3, CsPbBr3, CsPbCl3. • Thermodynamic differences between the high and low temperature phases decreases in the order CsPbI3, CsPbBr3 and CsPbCl3. • CsPbI3 perovskite is barely stable under ambient conditions, and thus may not be suitable for long term applications. Inorganic cesium lead halide (CsPbX 3 , X = I, Br, Cl) perovskites have sparked broad interest for photovoltaic applications, which, however, may be plagued by chemical and thermodynamic instabilities. This work reports calorimetric studies on the formation enthalpies of CsPbX 3 perovskites, confirming decreasing thermodynamic stability in the order CsPbCl 3 , CsPbBr 3 and CsPbI 3. Cesium lead iodide (CsPbI 3), one of the most studied inorganic lead halide perovskites, is shown to be only barely stable from a thermodynamic perspective. This order of increasing instability is consistent with the variation of Goldschmidt tolerance factor. The perovskites are high temperature entropy-stabilized phases with respect to low temperature polymorphs, with the thermodynamics of phase transitions reflecting the above thermodynamic trends. [ABSTRACT FROM AUTHOR]