The Role of Surface Tension in the Crystallization of Metal Halide Perovskites

Nucleation II.3.Growth II.4.Floatation III.Details of ST-ITC IV.Crystallinity analysis V. Trap state density analysis VI. PL spectra correction VII.Experimental analysis of the effect of surface tension VII.1.Concentration-dependent study of the solution surface tension VII.2.Temperature-dependent study of the solution surface tension VII.3.Estimation of the vial surface energy VII.4.Estimation of the solution-vial interface energy VIII.Raman study of MAPbBr3 PMF IX.Characteristics of the self-powered Schottky photodetector based on MAPbBr3 PMF X.Comparison of the state-of-the-art perovskite photodetectors based on single crystals S3 I. Materials and Methods Materials.Methylammonium bromide and methylammonium iodide were purchased from Dyesol Limited (Australia).Lead bromide (≥ 98%), lead iodide (99.999% trace metal basis), DMF (anhydrous, 99.8%) and GBL (≥ 99%) were purchased from Sigma-Aldrich.Tin bromide (II) was purchased from Alfa Aesar (99.2%).All salts and solvents were used as received without any further purification.All syntheses were carried in 4 ml ChemGlass reaction vials of 33 expansion borosilicate glass corresponding to ASTM E-438 Type 1-Class A, USP Type 1 and ISO 3585.For convenience, hereby we define molarity (M) as moles of solute per liter of solvent. Growth of MAPbI3 bulk single crystals with cuboid shape.A mixture of MAI (0.795 g, 5 mmol) and PbI2 (1.153 g, 2.5 mmol) was dissolved in 2 ml GBL and filtered through 0.45 µm PTFE filter.400 µL of the filtrate was transferred into a 4 ml vial, and the vial was placed on a hot plate at 60 °C.Then temperature was increased gradually to 96 °C when the formation of cuboid crystals was observed.Growth of MAPbBr3 PMFs.Solution A (1.5 M solution of MABr/PbBr2 in DMF prepared at room temperature) and solution B (4.2 M solution of MABr/PbBr2 in DMSO prepared at 60 °C) were mixed in different ratios (1:9, 2:8, 3:7, 4:6 and 5:5 by volume, respectively).300 µL of each mixture was transferred into a 4 ml vial, and the vials were placed on a hot plate at 60 °C.Then the temperature was increased gradually to 90-100 °C when the formation of PMFs in "1:9" and "2:8" mixtures was observed.The crystals were extracted using a spatula and then dried on a filter paper.Note 1: Aluminum foil was used to cover the crystallization setup in order to avoid the temperature fluctuations and determine the threshold concentration more accurately.