Study of the Crystallization of Metal Halide Perovskites Containing Additives via Differential Scanning Calorimetry

Control of the crystallization and morphology has been one of the major challenges in the design and fabrication of perovskite thin films. Recently, additives of different nature have been used to improve the crystallization and the quality of perovskite films. In this work, we study in detail the role of water (H 2 O), 1,8-diiodooctane (DIO), and dimethylsulfoxide (DMSO) as additives in the precursor solution of the CH 3 NH 3 PbI 3− x Cl x perovskite. Differential scanning calorimetry analysis revealed the thermal transitions for the crystallization of CH 3 NH 3 PbI 3− x Cl x perovskite depending on the chemical nature and physical properties of the additive. Information from thermograms enabled us to find optimal annealing ramps for each additive. We found that DIO produced changes mainly due to the interaction of this additive with the precursor salts in solution, while H 2 O due to its different boiling point compared to the DMF solvent. DMSO dramatically modified the thermal transitions to higher temperatures; however, high quality films were obtained only when the solvent engineering method is used.